tag:theconversation.com,2011:/uk/topics/higgs-boson-176/articlesHiggs boson – The Conversation2024-01-08T20:01:06Ztag:theconversation.com,2011:article/2202402024-01-08T20:01:06Z2024-01-08T20:01:06ZDark energy is one of the biggest puzzles in science and we’re now a step closer to understanding it<p>Over ten years ago, the <a href="https://www.darkenergysurvey.org/">Dark Energy Survey (DES)</a> began mapping the universe to find evidence that could help us understand the nature of the mysterious phenomenon known as dark energy. I’m one of more than 100 contributing scientists that have helped produce the final <a href="https://arxiv.org/pdf/2401.02929.pdf">DES measurement</a>, which has just been released at the <a href="https://aas.org/meetings/aas243">243rd American Astronomical Society meeting</a> in New Orleans.</p>
<p><a href="https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/">Dark energy</a> is estimated to make up nearly 70% of the observable universe, yet we still don’t understand what it is. While its nature remains mysterious, the impact of dark energy is felt on grand scales. Its primary effect is to drive the <a href="https://www.nobelprize.org/uploads/2018/06/advanced-physicsprize2011.pdf">accelerating expansion of the universe</a>.</p>
<p>The announcement in New Orleans may take us closer to a better understanding of this form of energy. Among other things, it gives us the opportunity to test our observations against an idea called the <a href="https://map.gsfc.nasa.gov/universe/uni_accel.html">cosmological constant</a> that was introduced by Albert Einstein in 1917 as a way of counteracting the effects of gravity in his equations to achieve a universe that was neither expanding nor contracting. Einstein later removed it from his calculations.</p>
<p>However, cosmologists later discovered that not only was the universe expanding, but the expansion was accelerating. This observation was attributed to the mysterious quantity called dark energy. Einstein’s concept of the cosmological constant could actually explain dark energy if it had a positive value (allowing it to conform to the accelerating expansion of the cosmos).</p>
<p>The DES results are the culmination of decades of work by researchers around the globe and provide one of the best measurements yet of an elusive parameter called “w”, which stands for the <a href="https://www.grc.nasa.gov/www/k-12/airplane/eqstat.html">“equation of state</a>” of dark energy. Since the discovery of dark energy in 1998, the value of its equation of state has been a fundamental question.</p>
<p>This state describes the ratio of pressure over energy density for a substance. Everything in the universe has an equation of state. </p>
<p>Its value tells you whether a substance is gas-like, relativistic (described by Einstein’s theory of relativity) or not, or if it behaves like a fluid. Working out this figure is the first step to really understanding the true nature of dark energy.</p>
<p>Our best theory for w predicts that it should be exactly minus one (w=-1). This prediction also assumes that dark energy is the cosmological constant proposed by Einstein.</p>
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Read more:
<a href="https://theconversation.com/the-euclid-spacecraft-will-transform-how-we-view-the-dark-universe-204245">The Euclid spacecraft will transform how we view the 'dark universe'</a>
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<h2>Subverting expectations</h2>
<p>An equation of state of minus one tells us that as the energy density of dark energy increases, so the negative pressure also increases. The more energy density in the universe, the more repulsion there is – in other words, matter pushes against other matter. This leads to an ever-expanding accelerating universe. It might sound a bit bizarre, as it is counterintuitive to everything we experience on Earth.</p>
<p>The work uses the most direct probe we have on the expansion history of the universe: <a href="https://newscenter.lbl.gov/2014/03/03/standard-candle-supernovae/">Type Ia supernovae</a>. These are a type of star explosion and they act as a kind of cosmic yardstick, allowing us to measure staggeringly large distances far into the universe. These distances can then be compared to our expectations. This is the same technique that was used to detect the existence of dark energy 25 years ago.</p>
<p>The difference now is in the size and quality of our sample of supernovae. Using new techniques, the DES team has 20 times more data, over a wide range of distances. This allows for one of the most precise ever measurements of w, giving a value of -0.8</p>
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<img alt="Vera Rubin Observatory." src="https://images.theconversation.com/files/568424/original/file-20240109-25-st53oq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568424/original/file-20240109-25-st53oq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568424/original/file-20240109-25-st53oq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568424/original/file-20240109-25-st53oq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568424/original/file-20240109-25-st53oq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568424/original/file-20240109-25-st53oq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568424/original/file-20240109-25-st53oq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Facilities such as the Vera Rubin Observatory will make further measurements.</span>
<span class="attribution"><a class="source" href="https://rubin.canto.com/v/gallery/album/HDSNU?display=curatedView&viewIndex=2&column=image&id=hfgkvecufl6krfopg1oq7bbv5g">H. Stockebrand/Rubin/NSF/AURARubinObs/NSF/AURA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>At first sight, this is not the precise minus one value that we predicted. This might indicate that it is not the cosmological constant. However, the uncertainty on this measurement is large enough to allow minus one at a 5% chance, or betting odds of only 20 to 1. This level of uncertainty is not good enough yet to say either way, but it’s an excellent start.</p>
<p>The detection of the Higgs Boson subatomic particle in 2012 at the Large Hadron Collider required odds of a million to one chance of being wrong. However, this measurement may signal <a href="https://www.wired.co.uk/article/big-rip-end-of-the-universe">the end of “Big Rip” models</a> which have equations of state that are more negative than one. In such models the universe would expand indefinitely at a faster and faster rate – eventually pulling apart galaxies, planetary systems and even space-time itself. That’s a relief.</p>
<p>As usual, scientists want more data and those plans are already well underway. The DES results suggest that our new techniques will work for future supernova experiments with <a href="https://www.esa.int/Science_Exploration/Space_Science/Euclid">ESA’s Euclid mission</a> (launched July 2023) and the new Vera Rubin Observatory in Chile. This observatory should soon use its telescope to take a first image of the sky following construction, giving a glimpse into its capabilities. </p>
<p>These next-generation telescopes could find thousands more supernovae, helping us make new measurements of the equation of state and shedding even more light on the nature of dark energy.</p><img src="https://counter.theconversation.com/content/220240/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Nichol is a member of the Dark Energy Survey collaboration.</span></em></p>The nature of dark energy remains one of the biggest puzzles in cosmology.Robert Nichol, Pro Vice-Chancellor and Executive Dean, University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1826752022-07-26T20:04:32Z2022-07-26T20:04:32ZA new book about 12 experiments that changed the world sidelines the role of beautiful theory in physics<figure><img src="https://images.theconversation.com/files/475022/original/file-20220720-14-qoiduh.jpg?ixlib=rb-1.1.0&rect=0%2C4%2C1467%2C930&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Simulation of lead ion collisions within the ALICE experiment at the Large Hadron Collider -- one of eight detector experiments.</span> <span class="attribution"><span class="source">CERN</span></span></figcaption></figure><p><a href="https://www.goodreads.com/book/show/59999316-the-matter-of-everything">The Matter of Everything</a> tells the history of physics through experiments. Any book about the history of science for a general audience will, of necessity, be something of a distortion. The question is whether the distortion is useful: does it offer a new perspective on the history of physics? While there is much to like about the book, I found it to be largely polemic and unhelpful.</p>
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<p><em>Review: The Matter of Everything: 12 experiments that changed the world – Suzie Sheehy (Bloomsbury)</em></p>
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<p>Here’s what I liked about the book: it is extremely detailed. It takes us through 12 important experiments within physics from roughly the last century and a half. </p>
<p>The experiments range from the study of X-rays and the nature of light in the early 20th century, to the early development of particle accelerators to detect and study subatomic particles throughout the 20th century, culminating in the modern era of Big Science and the use of the Large Hadron Collider to find the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a>. They are described in a manner that is rigorous and accessible. </p>
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<a href="https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/475012/original/file-20220720-20-qoiduh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A technician works in the LHC (Large Hadron Collider) tunnel of the European Organization for Nuclear Research, CERN, in 2016.</span>
<span class="attribution"><span class="source">Laurent Gillieron/AP</span></span>
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Read more:
<a href="https://theconversation.com/higgs-boson-ten-years-after-its-discovery-why-this-particle-could-unlock-new-physics-beyond-the-standard-model-186076">Higgs boson: ten years after its discovery, why this particle could unlock new physics beyond the standard model</a>
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<p>Rigour and accessibility clearly trade off, at least for a non-technical audience.
The book manages this trade off beautifully. Complex experiments are described in a manner that is easily understood.</p>
<p>The role that those experiments play in pushing forward the frontiers of particle physics – the study of an increasingly large array of very small pieces of reality, including those that constitute matter such as electrons, along with the forces that bind them – is also explained well. </p>
<p>It is done so without needing to take the reader through the details of some imposing theories, most notably: the various quantum field theories within the standard model of particle physics. </p>
<p>Author Suzie Sheehy, an Australian physicist with academic roles at Oxford and Melbourne universities, also does an incredible job of explaining the wider implications of the experiments considered. Sheehy is an expert in accelerator physics: the design and implementation of particle accelerators to conduct experiments.</p>
<p>Careful attention is paid to spin-off technologies developed in the course of building particle accelerators, including the development of Magnetic Resonance Imaging (MRIs) as well as the production of radio isotopes for use in medical imaging more generally. </p>
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<p>The point is well-made that developing these technologies was not an aim of scientific investigation but an unpredictable by-product. A word of caution underlies much of the discussion of these technologies: industry should be in the service of science, and not the other way around. </p>
<p>I also loved the book’s relish for the ingenuity of the inventor. For each of the 12 experiments described a common story unfolds: there is something we want to test but we just don’t know how to do it.</p>
<p>Scientists must invent new ways of managing electricity, magnetism, and more just so they can carry out their experiments. The world of experimental particle physics feels suddenly familiar: scientists are tinkerers, hammering out new pieces of equipment in much the same way one might invent a new kitchen utensil on the fly with some duct tape and a healthy dose of optimism.</p>
<h2>A distorted history</h2>
<p>As noted, The Matter of Everything is an inevitable distortion of the history of physics. One of the main distortions lies with the central premise of the book. The 12 experiments chosen are from the realm of particle physics. Whether by design or by accident, the history of 20th century physics is recast as the history of particle physics. </p>
<p>To say that this leaves a lot out, is an understatement. The standard model of particle physics is rivalled, in rigour and experimental confirmation, only by the general theory of relativity. </p>
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Read more:
<a href="https://theconversation.com/explainer-einsteins-theory-of-general-relativity-3481">Explainer: Einstein's Theory of General Relativity</a>
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<p>Whereas the standard model describes the world of particles and particle interactions, general relativity describes the large-scale structure of the universe and gravity.</p>
<p>In the 20th century, general relativity was both motivated and ultimately confirmed by a fascinating array of experiments, starting from the ingenious <a href="https://scienceworld.wolfram.com/physics/Michelson-MorleyExperiment.html">interferometer experiments</a> in the early 20th century to the detection of gravity waves in 2015. </p>
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Read more:
<a href="https://theconversation.com/gravitational-waves-discovered-scientists-explain-why-it-is-such-a-big-deal-54521">Gravitational waves discovered: scientists explain why it is such a big deal</a>
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<p>The focus on experiments relating to particle physics not only paints a strange picture of 20th century physics, but it also tends to cast the standard model in a rosy light. For we now know that the standard model is, in some sense, incomplete. The standard model “conflicts” with general relativity. The two theories are in need of replacement.</p>
<p>A more balanced telling of the history of 20th century physics might have included a wider array of experiments. Of course, a single book cannot cover everything. But some remarks on what is being left out should be offered. Otherwise, an idiosyncratic take on the history of 20th century physics quickly turns into a polemic retelling of where the “real” physics lies.</p>
<h2>Experiment and theory</h2>
<p>Why experiments? This is a question I kept asking myself throughout the book. Ultimately, the answer appears to be a political one. The book works hard to impress upon the reader the importance of experimental physics. Experiments are where the action is in science. Progress can only be made through gathering empirical data.</p>
<p>This focus on the experimenter as the pioneer, forging a path into new scientific terrain, is at best, a half truth. Companion to the experimenter is the theoretician. Theoretical work and experimental work generally go hand-in-hand. Theoretical physics, however, seems to be downplayed throughout the book.
This is perplexing, given that theories are essential to experimental work twice-over. </p>
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<a href="https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=545&fit=crop&dpr=1 600w, https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=545&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=545&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=685&fit=crop&dpr=1 754w, https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=685&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/474483/original/file-20220718-4540-tlj9xo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=685&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Trajectories in a Cloud Chamber.</span>
<span class="attribution"><a class="source" href="http://cerncourier.com/cws/article/cern/28742">Image from Gordon Fraser/CERN, http://cerncourier.com/cws/article/cern/28742)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>First, theories are typically needed to generate hypotheses for experimental testing. Much experimental work tests the predictions of known theories in order to confirm them. There are, of course, cases in which an experiment is conducted and produces results that challenge all known theories. But even then, it is the interplay between theory and experiment that drives science forward. </p>
<p>Second, theories are needed to make sense of empirical data. A theory of some kind is typically needed to understand how a given experiment works. </p>
<p>The Large Hadron Collider – a massive ring of electromagnets used to accelerate particles to high velocities before smashing them together, to see what they’re made of – is a case in point. The experiment is so complex that understanding it requires grasping an array of theories from different areas of science. Experimental data in a vacuum is virtually meaningless. Theories provide context for experimental data.</p>
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Read more:
<a href="https://theconversation.com/new-physics-at-the-large-hadron-collider-scientists-are-excited-but-its-too-soon-to-be-sure-157871">New physics at the Large Hadron Collider? Scientists are excited, but it's too soon to be sure</a>
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<p>The suppression of theoretical work in physics is part of the book’s gimmick. But, again, the picture this conveys of 20th century physics is unrealistic. The story of 20th century physics is as much one of beautiful theory, as it is of ingenious experiment. Again, it is hard not to see the focus on experiment as something of a normative statement on how science ought to be done.</p>
<h2>Lost voices</h2>
<p>People play a large role in the Matter of Everything. Glorious experimental machinery is set against the backdrop of scientist-inventors who tinker and toil. This focus on people is welcome. It helps to humanise the story of 20th century physics, and give the reader a sense that they too could contribute to science, if only they mucked around in the shed long enough. </p>
<p>That being said, the book might have said more about scientists who are widely acknowledged to have been unjustly neglected in the history of their field. As the book itself acknowledges, there is, for example, a need to tell the story of women scientists.</p>
<p>Given this, I found the omission of Marie Curie, and her daughter Irene, striking. Marie and Irene pass in and out of the book at various places, but their story is never properly told. </p>
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<a href="https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=646&fit=crop&dpr=1 600w, https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=646&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=646&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=811&fit=crop&dpr=1 754w, https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=811&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/475019/original/file-20220720-12-t9q7r1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=811&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Marie and Irene Curie.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
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Read more:
<a href="https://theconversation.com/radioactive-new-marie-curie-biopic-inspires-but-resonates-uneasily-for-women-in-science-148986">Radioactive: new Marie Curie biopic inspires, but resonates uneasily for women in science</a>
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<p>This is particularly odd given that both were involved in experimental work in particle physics, and one was a Nobel laureate. Ultimately, the book doesn’t fully heed its own warning, and what we are left with is a history of physics with notable gaps. This is a shame, since it was an opportunity to set the record straight.</p>
<h2>Limitations</h2>
<p>Overall, The Matter of Everything suffers from some serious limitations. It claims to be a history of 20th century physics but, at best, tells the story of experimental particle physics. </p>
<p>Theoretical work is missing, as are some of the experiments that relate to gravitational work in physics. The book also has significant gaps when it comes to the scientists themselves. </p>
<p>I thus don’t recommend the book as a complete history of 20th century physics. But read it if you’re interested in particle accelerators, and if you’re keen to know why they matter so much to everyday life, and not just big science.</p><img src="https://counter.theconversation.com/content/182675/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sam Baron receives funding from the Australian Research Council.</span></em></p>The Matter of Everything is a partial account of the history of physics, which leaves out a lot, including the story of some key women scientists.Sam Baron, Associate professor, Australian Catholic UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1860762022-07-01T14:46:48Z2022-07-01T14:46:48ZHiggs boson: ten years after its discovery, why this particle could unlock new physics beyond the standard model<figure><img src="https://images.theconversation.com/files/472056/original/file-20220701-13-xm3fo4.jpeg?ixlib=rb-1.1.0&rect=24%2C26%2C1556%2C1046&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Press conference for the announcement of the Higgs boson discovery.</span> <span class="attribution"><span class="source">Cern</span></span></figcaption></figure><p>Ten years ago, scientists announced <a href="https://theconversation.com/nobel-prize-in-physics-goes-to-discovery-of-the-higgs-boson-19014">the discovery of the Higgs boson</a>, which helps explain why elementary particles (the smallest building blocks of nature) have mass. For particle physicists, this was the end of a decades-long and hugely difficult journey – and arguably the most important result in the history of the field. But this end also marked the beginning of a new era of experimental physics.</p>
<p>In the past decade, measurements of the properties of the Higgs boson have confirmed the predictions of the <a href="https://theconversation.com/explainer-what-are-fundamental-particles-38339">standard model of particle physics</a> (our best theory for particles). But it has also raised questions about the limitations of this model, such as whether there’s a more fundamental theory of nature. </p>
<figure class="align-right ">
<img alt="Image of Peter Higgs." src="https://images.theconversation.com/files/472033/original/file-20220701-18-d0lxh5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/472033/original/file-20220701-18-d0lxh5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472033/original/file-20220701-18-d0lxh5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472033/original/file-20220701-18-d0lxh5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472033/original/file-20220701-18-d0lxh5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472033/original/file-20220701-18-d0lxh5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472033/original/file-20220701-18-d0lxh5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Physicist Peter Higgs.</span>
<span class="attribution"><span class="source">wikipedia</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Physicist <a href="https://www.nobelprize.org/prizes/physics/2013/higgs/facts/">Peter Higgs</a> predicted the Higgs boson in a series of papers between 1964 and 1966, as an inevitable consequence of the mechanism responsible for giving elementary particles mass. This theory suggests particle masses are a consequence of elementary particles interacting with a field, dubbed the Higgs field. And according to the same model, such a field should also give rise to a Higgs particle – meaning if the Higgs boson wasn’t there, this would ultimately falsify the entire theory.</p>
<p>But it soon became clear that discovering this particle would be challenging. When three theoretical physicists calculated the properties of a Higgs boson, <a href="https://www.sciencedirect.com/science/article/pii/0550321376903825?via%3Dihub">they concluded with an apology</a>. “We apologize to experimentalists for having no idea what is the mass of the Higgs boson … and for not being sure of its couplings to other particles … For these reasons, we do not want to encourage big experimental searches for the Higgs boson.”</p>
<p>It took until 1989 for the first experiment with a serious chance of discovering the Higgs boson to begin its search. The idea was to smash particles together with such high energy that a Higgs particle could be created in a 27km long tunnel at Cern in Geneva, Switzerland – the largest electron-positron (a positron is almost identical to an electron but has opposite charge) collider ever built. It ran for 11 years, but its maximum energy turned out to be just 5% too low to produce the Higgs boson.</p>
<p>Meanwhile, the most ambitious American collider in history, the <a href="https://www.fnal.gov/pub/tevatron/tevatron-accelerator.html#:%7E:text=The%20Tevatron%20was%20the%20second,around%20a%20four%2Dmile%20circumference.">Tevatron</a>, had started taking data at Fermilab, close to Chicago. The Tevatron collided protons (which, along with neutrons, make up the atomic nucleus) and antiprotons (nearly identical to protons but with opposite charge) with an energy five times higher than what was achieved in Geneva – surely, enough to make the Higgs. But proton-antiproton collisions produce a lot of debris, making it much harder to extract the signal from the data. In 2011, the Tevatron ceased operations – the Higgs boson escaped detection again. </p>
<p>In 2010, the <a href="https://theconversation.com/explainer-how-does-an-experiment-at-the-large-hadron-collider-work-42846">Large Hadron Collider</a> (LHC) began colliding protons with seven times more energy than the Tevatron. Finally, on July 4 2012, two independent experiments at Cern had each collected enough data to declare the discovery of the Higgs boson. In the following year, Higgs and his collaborator François Englert <a href="https://www.nobelprize.org/prizes/physics/2013/summary/">won the Nobel prize</a> “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles”.</p>
<p>This almost sells it short. Without the Higgs boson, the whole theoretical framework describing particle physics at its smallest scales breaks apart. Elementary particles would be massless, there would be no atoms, no humans, no solar systems and no structure in the universe. </p>
<h2>Trouble on the horizon</h2>
<p>Yet the discovery has raised new, fundamental questions. Experiments at Cern have continued to probe the Higgs boson. Its properties not only determine the masses of elementary particles, but also how stable they are. As it stands, the results indicate that <a href="https://link.springer.com/article/10.1007/JHEP08(2012)098">our universe isn’t in a perfectly stable state</a>. Instead, similar to ice at the melting point, the universe could suddenly undergo a rapid “phase transition”. But rather than going from a solid to a liquid, like ice transitioning to water, this would involve crucially changing the masses – and the laws of nature in the universe.</p>
<p>The fact that the universe nevertheless seems stable suggests something might be missing in the calculations – something we have not discovered yet. </p>
<p>After a three-year hiatus for maintenance and upgrades, collisions at the LHC are now about to resume at an unprecedented energy, nearly double that used to detect the Higgs boson. This could help find missing particles that move our universe away from the apparent knife-edge between being stable and rapidly undergoing a phase transition.</p>
<p>The experiment could help answer other questions, too. Could the unique properties of the Higgs boson make it a portal to discovering dark matter, the invisible substance making up most of the matter in the universe? Dark matter is not charged. And the Higgs boson <a href="https://www.sciencedirect.com/science/article/pii/S0146641021000351?via%3Dihub">has a unique way of interacting</a> with uncharged matter.</p>
<p>The same unique properties have made physicists question whether the Higgs boson might not be a fundamental particle after all. Could there be a new, unknown force beyond the other forces of nature – gravity, electromagnetism and the weak and strong nuclear forces? Perhaps a force that binds so far unknown particles into a composite object we call the Higgs boson? </p>
<figure class="align-center ">
<img alt="Image of the LHC experiment at Cern." src="https://images.theconversation.com/files/472031/original/file-20220701-16-v4td7n.jpg?ixlib=rb-1.1.0&rect=89%2C50%2C4096%2C1911&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472031/original/file-20220701-16-v4td7n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=277&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472031/original/file-20220701-16-v4td7n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=277&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472031/original/file-20220701-16-v4td7n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=277&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472031/original/file-20220701-16-v4td7n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=349&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472031/original/file-20220701-16-v4td7n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=349&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472031/original/file-20220701-16-v4td7n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=349&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It’s been 10 years since the Higgs was discovered.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/switzerland-april-2010-cern-european-organization-1287557629">D-VISIONS/Shutterstock</a></span>
</figcaption>
</figure>
<p>Such theories may help to address the controversial <a href="https://theconversation.com/the-standard-model-of-particle-physics-may-be-broken-an-expert-explains-182081">results of recent measurements</a> which suggest some particles do not behave exactly the way the standard model suggests they should. So studying the Higgs boson is vital to working out whether there is physics to be discovered beyond the standard model.</p>
<p>Eventually, the LHC will run into the same problem as the Tevatron did. Proton collisions are messy and the energy of its collisions will only reach so far. Even though we have the full arsenal of modern particle physics – including sophisticated detectors, advanced detection methods and machine learning – at our disposal, there is a limit to what the LHC can achieve. </p>
<p>A future high-energy collider, specifically designed to produce Higgs bosons, would enable us to precisely measure its most important properties, including how the Higgs boson interacts with other Higgs bosons. This in turn would determine how the Higgs boson interacts with its own field. Studying this interaction could therefore help us probe the underlying process which gives particles masses. Any disagreement between the theoretical prediction and a future measurement <a href="https://journals.aps.org/prd/abstract/10.1103/PhysRevD.78.063518">would be a crystal-clear sign</a> that we need to invent brand new physics.</p>
<p>These measurements will have a profound impact that reaches far beyond collider physics, guiding or constraining our understanding of the origin of dark matter, the birth of our universe – and, perhaps, its ultimate fate.</p><img src="https://counter.theconversation.com/content/186076/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Bauer is an associate professor at the Institute for Particle Physics Phenomenology (IPPP) at Durham University. He receives funding from UKRI through a Future Leaders fellowhip. The IPPP is funded by the Science and Technology and Facilities Council (STFC). Martin Bauer is a member of the STFC Science Board.</span></em></p><p class="fine-print"><em><span>Stephen Jones is an assistant professor at the Institute for Particle Physics Phenomenology (IPPP) at Durham University. He receives funding from the Royal Society through a University Research Fellowship. The IPPP is funded by the Science and Technology and Facilities Council (STFC).</span></em></p>Studying the properties of the Higgs boson could throw up some shocking truths about the nature of reality.Martin Bauer, Associate Professor of Physics, Durham UniversityStephen Jones, Assistant Professor of Physics, Durham UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1820812022-05-06T15:43:30Z2022-05-06T15:43:30ZThe standard model of particle physics may be broken – an expert explains<figure><img src="https://images.theconversation.com/files/461804/original/file-20220506-16-hdf1s0.jpg?ixlib=rb-1.1.0&rect=220%2C110%2C7004%2C4724&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The storage-ring magnet for the Muon G-2 experiment at Fermilab.</span> <span class="attribution"><a class="source" href="https://vms.fnal.gov/asset/detail?recid=1950114">Reidar Hahn/wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>As a physicist working at the Large Hadron Collider (LHC) at Cern, one of the most frequent questions I am asked is “When are you going to find something?”. Resisting the temptation to sarcastically reply “Aside from the Higgs boson, which won the Nobel Prize, and a whole slew of new composite particles?”, I realise that the reason the question is posed so often is down to how we have portrayed progress in particle physics to the wider world.</p>
<p>We often talk about progress in terms of discovering new particles, and it often is. Studying a new, very heavy particle helps us view underlying physical processes – often without annoying background noise. That makes it easy to explain the value of the discovery to the public and politicians.</p>
<p>Recently, however, a series of precise measurements of already known, bog-standard particles and processes have threatened to shake up physics. And with the LHC getting ready to run <a href="https://www.scientificamerican.com/article/large-hadron-collider-seeks-new-particles-after-major-upgrade/">at higher energy and intensity</a> than ever before, it is time to start discussing the implications widely.</p>
<p>In truth, particle physics has always proceeded in two ways, of which new particles is one. The other is by making very precise measurements that test the predictions of theories and look for deviations from what is expected. </p>
<p>The early evidence for Einstein’s theory of general relativity, for example, came from discovering small deviations in the apparent positions of stars and from the motion of Mercury in its orbit. </p>
<h2>Three key findings</h2>
<p>Particles obey a counter-intuitive but hugely successful theory called quantum mechanics. This theory shows that particles far too massive to be made directly in a lab collision can still influence what other particles do (through something called “quantum fluctuations”). Measurements of such effects are very complex, however, and much harder to explain to the public. </p>
<p>But recent results hinting at unexplained new physics beyond the standard model are of this second type. Detailed <a href="https://theconversation.com/new-physics-latest-results-from-cern-further-boost-tantalising-evidence-170133">studies from the LHCb experiment</a> found that a particle known as a beauty quark (quarks make up the protons and neutrons in the atomic nucleus) “decays” (falls apart) into an electron much more often than into a muon – the electron’s heavier, but otherwise identical, sibling. According to the standard model, this shouldn’t happen – hinting that new particles or even forces of nature may influence the process. </p>
<figure class="align-center ">
<img alt="Image of the LHCb experiment." src="https://images.theconversation.com/files/390889/original/file-20210322-19-nytkho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/390889/original/file-20210322-19-nytkho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/390889/original/file-20210322-19-nytkho.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/390889/original/file-20210322-19-nytkho.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/390889/original/file-20210322-19-nytkho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/390889/original/file-20210322-19-nytkho.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/390889/original/file-20210322-19-nytkho.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">LHCb experiment.</span>
<span class="attribution"><span class="source">Cern</span></span>
</figcaption>
</figure>
<p>Intriguingly, though, measurements of similar processes involving “top quarks” from the ATLAS experiment at the LHC show this decay <a href="https://www.nature.com/articles/s41567-021-01236-w">does happen at equal rates</a> for electrons and muons.</p>
<p>Meanwhile, the Muon g-2 experiment at Fermilab in the US has recently made <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">very precise studies</a> of how muons “wobble” as their “spin” (a quantum property) interacts with surrounding magnetic fields. It found a small but significant deviation from some theoretical predictions – again suggesting that unknown forces or particles may be at work.</p>
<p>The <a href="https://www.nature.com/articles/d41586-022-01014-5">latest surprising result</a> is a measurement of the mass of a fundamental particle called the <a href="https://home.cern/science/physics/w-boson-sunshine-and-stardust">W boson</a>, which carries the weak nuclear force that governs radioactive decay. After many years of data taking and analysis, the experiment, also at Fermilab, suggests it is significantly heavier than theory predicts – deviating by an amount that would not happen by chance in more than a million million experiments. Again, it may be that yet undiscovered particles are adding to its mass.</p>
<p>Interestingly, however, this also disagrees with some lower-precision measurements from the LHC (presented in <a href="https://link.springer.com/article/10.1140/epjc/s10052-017-5475-4">this study</a> and <a href="https://link.springer.com/article/10.1140/epjc/s10052-018-6354-3">this one</a>).</p>
<h2>The verdict</h2>
<p>While we are not absolutely certain these effects require a novel explanation, the evidence seems to be growing that some new physics is needed.</p>
<p>Of course, there will be almost as many new mechanisms proposed to explain these observations as there are theorists. Many will look to various forms of “<a href="https://home.cern/science/physics/supersymmetry#:%7E:text=Supersymmetry%20is%20an%20extension%20of,mass%20of%20the%20Higgs%20boson.">supersymmetry</a>”. This is the idea that there are twice as many fundamental particles in the standard model than we thought, with each particle having a “super partner”. These may involve additional Higgs bosons (associated with the field that gives fundamental particles their mass).</p>
<p>Others will go beyond this, invoking less recently fashionable ideas such as “<a href="https://www.forbes.com/sites/brucedorminey/2014/11/19/cerns-higgs-discovery-as-portal-to-new-technicolor-physics/?sh=3deeed1925d8">technicolor</a>”, which would imply that there are additional forces of nature (in addition to gravity, electromagnetism and the weak and strong nuclear forces), and might mean that the Higgs boson is in fact a composite object made of other particles. Only experiments will reveal the truth of the matter - which is good news for experimentalists.</p>
<p>The experimental teams behind the new findings are all well respected and have worked on the problems for a long time. That said, it is no disrespect to them to note that these measurements are extremely difficult to make. What’s more, predictions of the standard model usually require calculations where approximations have to be made. This means different theorists can predict slightly different masses and rates of decay depending on the assumptions and level of approximation made. So, it may be that when we do more accurate calculations, some of the new findings will fit with the standard model. </p>
<p>Equally, it may be the researchers are using subtly different interpretations and so finding inconsistent results. Comparing two experimental results requires careful checking that the same level of approximation has been used in both cases. </p>
<p>These are both examples of sources of “systematic uncertainty”, and while all concerned do their best to quantify them, there can be unforeseen complications that under- or over-estimate them.</p>
<p>None of this makes the current results any less interesting or important. What the results illustrate is that there are multiple pathways to a deeper understanding of the new physics, and they all need to be explored. </p>
<p>With the restart of the LHC, there are still prospects of new particles being made through rarer processes or found hidden under backgrounds that we have yet to unearth.</p><img src="https://counter.theconversation.com/content/182081/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Jones receives funding from STFC. I am a member of the ATLAS Collaboration </span></em></p>A series of thrilling research means physicists may have to start inventing brand new physics.Roger Jones, Professor of Physics, Head of Department, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1810282022-04-14T12:13:39Z2022-04-14T12:13:39ZA decade of science and trillions of collisions show the W boson is more massive than expected – a physicist on the team explains what it means for the Standard Model<figure><img src="https://images.theconversation.com/files/458000/original/file-20220413-16-ptwkj1.jpg?ixlib=rb-1.1.0&rect=235%2C188%2C5006%2C3143&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Measuring the mass of W bosons took 10 years – and the result was not what physicists expected.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/balls-balancing-on-scale-royalty-free-image/1284113909">PM Images/Digital Vision via Getty Images</a></span></figcaption></figure><p>“You can do it quickly, you can do it cheaply, or you can do it right. We did it right.” These were some of the opening remarks from David Toback, leader of the Collider Detector at Fermilab, as he announced the results of a decadelong experiment to <a href="https://doi.org/10.1126/science.abk1781">measure the mass of a particle called the W boson</a>.</p>
<p>I am a <a href="https://physics.ucdavis.edu/directory/faculty/john-conway">high energy particle physicist</a>, and I am part of the team of hundreds of scientists that built and ran the Collider Detector at Fermilab in Illinois – known as CDF.</p>
<p>After trillions of collisions and years of data collection and number crunching, the CDF team found that the W boson has <a href="https://doi.org/10.1126/science.abk1781">slightly more mass than expected</a>. Though the discrepancy is tiny, the results, described in a paper published in Science on April 7, 2022, have <a href="https://doi.org/10.1038/d41586-022-01014-5">electrified the particle physics world</a>. If the measurement is correct, it is <a href="https://theconversation.com/2021-a-year-physicists-asked-what-lies-beyond-the-standard-model-173132">yet another strong signal</a> that there are missing pieces to the physics puzzle of how the universe works.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing many particles." src="https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=574&fit=crop&dpr=1 600w, https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=574&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=574&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=721&fit=crop&dpr=1 754w, https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=721&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/458003/original/file-20220413-17-m5k8mw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=721&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Standard Model of particle physics describes the particles that make up the mass and forces of the universe.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Standard_Model_of_Elementary_Particles.svg#/media/File:Standard_Model_of_Elementary_Particles.svg">MissMJ/WikimediaCommons</a></span>
</figcaption>
</figure>
<h2>A particle that carries the weak force</h2>
<p>The <a href="https://theconversation.com/the-standard-model-of-particle-physics-the-absolutely-amazing-theory-of-almost-everything-94700">Standard Model of particle physics</a> is science’s current best framework for the basic laws of the universe and <a href="https://www.iop.org/explore-physics/physics-stepping-stones/standard-model">describes three basic forces</a>: the electromagnetic force, the weak force and the strong force. </p>
<p>The strong force holds atomic nuclei together. But some nuclei are unstable and undergo radioactive decay, slowly releasing energy by emitting particles. This process is driven by the weak force, and since the early 1900s, physicists sought an explanation for why and how atoms decay.</p>
<p>According to the Standard Model, forces are transmitted by particles. In the 1960s, a series of <a href="https://www.routledge.com/Weak-Neutral-Currents-The-Discovery-Of-The-Electro-weak-Force/Cline/p/book/9780367216139">theoretical and experimental breakthroughs</a> proposed that the weak force is transmitted by particles called W and Z bosons. It also postulated that a third particle, the Higgs boson, is what gives all other particles – including W and Z bosons – mass.</p>
<p>Since the advent of the Standard Model in the 1960s, scientists have been working their way down the list of predicted yet undiscovered particles and measuring their properties. In 1983, two experiments at CERN in Geneva, Switzerland, <a href="https://doi.org/10.1016/0370-2693(83)90860-2">captured the first evidence of the existence of the W boson</a>. It appeared to have the mass of roughly a medium-sized atom such as bromine. </p>
<p>By the 2000s, there was just one piece missing to complete the Standard Model and tie everything together: the Higgs boson. I helped search for the Higgs boson on three successive experiments, and at last we <a href="https://home.cern/science/physics/higgs-boson">discovered it in 2012</a> at the Large Hadron Collider at CERN. </p>
<p>The Standard Model was complete, and all the measurements we made hung together beautifully with the predictions.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large yellow tube surrounded by electronics." src="https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/458007/original/file-20220413-14-a1ml2j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Collider Detector at Fermilab collected data from trillions of collisions that produced millions of W bosons.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Collider_Detector_at_Fermilab.jpg#/media/File:Collider_Detector_at_Fermilab.jpg">Bodhita/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Measuring W bosons</h2>
<p>Testing the Standard Model is fun – you just smash particles together at very high energies. These collisions briefly produce heavier particles that then decay back into lighter ones. Physicists use huge and very sensitive detectors at places like Fermilab and CERN to measure the properties and interactions of the particles produced in these collisions. </p>
<p>In CDF, W bosons are produced about <a href="http://www.hep.ph.ic.ac.uk/%7Ewstirlin/plots/crosssections2012_v5.pdf">one out of every 10 million times</a> when a proton and an antiproton collide. Antiprotons are the antimatter version of protons, with exactly the same mass but opposite charge. Protons are made of smaller fundamental particles called quarks, and antiprotons are made of antiquarks. It is the collision between quarks and antiquarks that <a href="https://inspirehep.net/literature/261813">create W bosons</a>. W bosons decay so fast that they are impossible to measure directly. So physicists track the energy produced from their decay to measure the mass of W bosons.</p>
<p>In the 40 years since scientists first detected evidence of the W boson, successive experiments have attained ever more precise measurements of its mass. But it is only since the measurement of the Higgs boson – since it gives mass to all other particles – that researchers could check the measured mass of W bosons against the <a href="https://doi.org/10.1007/JHEP12(2013)084">mass predicted by the Standard Model</a>. The prediction and the experiments always matched up – until now.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing two circles near a line." src="https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=567&fit=crop&dpr=1 600w, https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=567&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=567&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=713&fit=crop&dpr=1 754w, https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=713&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/458024/original/file-20220413-23-edjk9x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=713&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The new measurement of the W boson (red circle) is much farther from the mass predicted by the Standard Model (purple line) and also greater than the preliminary measurement from the experiment.</span>
<span class="attribution"><a class="source" href="https://www.science.org/doi/10.1126/science.abk1781">CDF Collaboration via Science Magazine</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Unexpectedly heavy</h2>
<p>The CDF detector at Fermilab is excellent at accurately measuring W bosons. From 2001 to 2011, the accelerator collided protons with antiprotons trillions of times, producing millions of W bosons and recording as much data as possible from each collision.</p>
<p>The Fermilab team published <a href="https://inspirehep.net/literature/1097099">initial results</a> using a fraction of the data in 2012. We found the mass to be slightly off, but close to the prediction. The team then spent a decade painstakingly analyzing the full data set. The process included numerous internal cross-checks and required years of computer simulations. To avoid any bias creeping into the analysis, nobody could see any results until the full calculation was complete.</p>
<p>When the physics world finally saw the result on April 7, 2022, we were all surprised. Physicists measure elementary particle masses in units of millions of electron volts – shortened to MeV. The W boson’s mass <a href="https://doi.org/10.1126/science.abk1781">came out to be 80,433 MeV</a> – 70 MeV higher than what the Standard Model predicts it should be. This may seem like a tiny excess, but the measurement is accurate to within 9 MeV. This is a deviation of nearly eight times the margin of error. When my colleagues and I saw the result, our reaction was a resounding “wow!” </p>
<h2>What this means for the Standard Model</h2>
<p>The fact that the measured mass of the W boson doesn’t match the predicted mass within the Standard Model could mean three things. Either the math is wrong, the measurement is wrong or there is something missing from the Standard Model.</p>
<p>First, the math. In order to calculate the W boson’s mass, physicists use the mass of the Higgs boson. CERN experiments have allowed physicists to <a href="https://doi.org/10.1007/JHEP10(2012)140">measure the Higgs boson mass</a> to within a quarter-percent. Additionally, theoretical physicists have been <a href="https://doi.org/10.1103/PhysRevD.96.093005">working on the W boson mass calculations for decades</a>. While the math is sophisticated, the prediction is solid and not likely to change.</p>
<p>The next possibility is a flaw in the experiment or analysis. Physicists all over the world are already reviewing the result to try to poke holes in it. Additionally, future experiments at CERN may eventually achieve a more precise result that will either confirm or refute the Fermilab mass. But in my opinion, the experiment is as good a measurement as is currently possible.</p>
<p>That leaves the last option: There are unexplained particles or forces causing the upward shift in the W boson’s mass. Even before this measurement, some theorists had <a href="https://doi.org/10.1126/science.abk1781">proposed potential new particles or forces</a> that would result in the observed deviation. In the coming months and years, I expect a raft of new papers seeking to explain the puzzling mass of W bosons. </p>
<p>As a particle physicist, I am confident in saying that there must be more physics waiting to be discovered beyond the Standard Model. If this new result holds up, it will be the latest in a series of findings showing that the Standard Model and real-world measurements often <a href="https://theconversation.com/proof-of-new-physics-from-the-muons-magnetic-moment-maybe-not-according-to-a-new-theoretical-calculation-157829">don’t quite match</a>. It is these mysteries that give physicists new clues and new reasons to keep searching for fuller understanding of matter, energy, space and time.</p>
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<p class="fine-print"><em><span>John Conway receives funding from US Department of Energy and US National Science Foundation</span></em></p>A decadelong experiment produced the most accurate measurement yet of the mass of W bosons. These particles are responsible for the weak force, and the result is more evidence for undiscovered physics.John Conway, Professor of Physics, University of California, DavisLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1731322021-12-22T13:12:07Z2021-12-22T13:12:07Z2021: a year physicists asked, ‘What lies beyond the Standard Model?’<figure><img src="https://images.theconversation.com/files/438717/original/file-20211221-48250-esf86c.jpg?ixlib=rb-1.1.0&rect=45%2C21%2C1566%2C1027&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Experiments at the Large Hadron Collider in Europe, like the ATLAS calorimeter seen here, are providing more accurate measurements of fundamental particles.</span> <span class="attribution"><a class="source" href="https://cds.cern.ch/record/910381">Maximilien Brice</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>If you ask a physicist like me to explain how the world works, my lazy answer might be: “It follows the Standard Model.”</p>
<p><a href="https://theconversation.com/the-standard-model-of-particle-physics-the-absolutely-amazing-theory-of-almost-everything-94700">The Standard Model</a> explains the fundamental physics of how the universe works. It has endured over 50 trips around the Sun despite experimental physicists constantly probing for cracks in the model’s foundations. </p>
<p>With few exceptions, it has stood up to this scrutiny, passing experimental test after experimental test with flying colors. But this wildly successful model has conceptual gaps that suggest there is a bit more to be learned about how the universe works.</p>
<p>I am a <a href="https://scholar.google.com/citations?user=N_cqAjYAAAAJ&hl=en&oi=sra">neutrino physicist</a>. <a href="https://neutrinos.fnal.gov/whats-a-neutrino/">Neutrinos</a> represent three of the <a href="https://www.iop.org/explore-physics/physics-stepping-stones/standard-model">17 fundamental particles in the Standard Model</a>. They zip through every person on Earth at all times of day. I study the properties of interactions between <a href="https://neutrinos.fnal.gov/whats-a-neutrino/">neutrinos</a> and normal matter particles.</p>
<p>In 2021, physicists around the world ran a number of experiments that probed the Standard Model. Teams measured basic parameters of the model more precisely than ever before. Others investigated the fringes of knowledge where the best experimental measurements don’t quite match the predictions made by the Standard Model. And finally, groups built more powerful technologies designed to push the model to its limits and potentially discover new particles and fields. If these efforts pan out, they could lead to a more complete theory of the universe in the future.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing the particles of the Standard Model." src="https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438763/original/file-20211222-17-y5l097.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Standard Model of physics allows scientists to make incredibly accurate predictions about how the world works, but it doesn’t explain everything.</span>
<span class="attribution"><a class="source" href="https://cds.cern.ch/images/OPEN-PHO-CHART-2015-001-1/">CERN</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<h2>Filling holes in Standard Model</h2>
<p>In 1897, J.J. Thomson discovered the first fundamental particle, the electron, using nothing more than <a href="https://www.britannica.com/science/atom/Discovery-of-electrons">glass vacuum tubes and wires</a>. More than 100 years later, physicists are still discovering new pieces of the Standard Model.</p>
<p><a href="https://www.energy.gov/science/doe-explainsthe-standard-model-particle-physics">The Standard Model</a> is a <a href="https://theconversation.com/the-standard-model-of-particle-physics-the-absolutely-amazing-theory-of-almost-everything-94700">predictive framework</a> that does two things. First, it explains what the basic particles of matter are. These are things like electrons and the quarks that make up protons and neutrons. Second, it predicts how these matter particles interact with each other using “messenger particles.” These are called bosons – they include photons and the famous Higgs boson – and they communicate the basic forces of nature. The Higgs boson wasn’t <a href="https://atlas.cern/updates/feature/higgs-boson">discovered until 2012</a> after decades of work at CERN, the huge particle collider in Europe.</p>
<p>The Standard Model is incredibly good at predicting many aspects of how the world works, but it does have some holes.</p>
<p>Notably, it does not include any description of gravity. While Einstein’s theory of <a href="https://theconversation.com/why-does-gravity-pull-us-down-and-not-up-162141">General Relativity describes how gravity works</a>, physicists have not yet discovered a particle that conveys the force of gravity. A proper “Theory of Everything” would do everything the Standard Model can, but also include the messenger particles that communicate how gravity interacts with other particles.</p>
<p>Another thing the Standard Model can’t do is explain why any particle has a certain mass – physicists must measure the mass of particles directly using experiments. Only after experiments give physicists these exact masses can they be used for predictions. The better the measurements, the better the predictions that can be made.</p>
<p>Recently, physicists on a team at CERN measured <a href="https://atlas.cern/updates/briefing/twice-higgs-twice-challenge">how strongly the Higgs boson feels itself</a>. Another CERN team also measured the Higgs boson’s mass <a href="https://cms.cern/news/cms-precisely-measures-mass-higgs-boson">more precisely than ever before</a>. And finally, there was also progress on measuring the mass of neutrinos. Physicists know neutrinos have more than zero mass but less than the amount currently detectable. A team in Germany has continued to refine the techniques that could allow them to <a href="https://www.katrin.kit.edu/index.php">directly measure the mass of neutrinos</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A blue circular particle acellerator." src="https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438712/original/file-20211221-15-17289qh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Projects like the Muon g-2 experiment highlight discrepancies between experimental measurements and predictions of the Standard Model that point to problems somewhere in the physics.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Fermilab_g-2_(E989)_ring.jpg#/media/File:Fermilab_g-2_(E989)_ring.jpg">Reidar Hahn/WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Hints of new forces or particles</h2>
<p>In April 2021, members of the <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">Muon g-2 experiment at Fermilab announced</a> their first <a href="https://theconversation.com/how-we-found-hints-of-new-particles-or-forces-of-nature-and-why-it-could-change-physics-158564">measurement of the magnetic moment of the muon</a>. The muon is one of the fundamental particles in the Standard Model, and this measurement of one of its properties is the most accurate to date. The reason this experiment was important was because the measurement didn’t perfectly match the Standard Model prediction of the magnetic moment. Basically, muons don’t behave as they should. This finding could point to <a href="https://news.uchicago.edu/story/what-muon-g-2-results-mean-how-we-understand-universe">undiscovered particles that interact with muons</a>.</p>
<p>But simultaneously, in April 2021, physicist Zoltan Fodor and his colleagues showed how they used a mathematical method called Lattice QCD to <a href="https://theconversation.com/proof-of-new-physics-from-the-muons-magnetic-moment-maybe-not-according-to-a-new-theoretical-calculation-157829">precisely calculate the muon’s magnetic moment</a>. Their theoretical prediction is different from old predictions, still works within the Standard Model and, importantly, matches experimental measurements of the muon.</p>
<p>The disagreement between the previously accepted predictions, this new result and the new prediction must be reconciled before physicists will know if the experimental result is truly beyond the Standard Model.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A spinning galaxy in space." src="https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=436&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=436&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=436&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=548&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=548&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438713/original/file-20211221-129369-zkmpnf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=548&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">New tools will help physicists search for dark matter and other things that could help explain mysteries of the universe.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/dark-matter-halo-surrounding-galaxy-royalty-free-illustration/932730112?adppopup=true">Mark Garlick/Science Photo Library via Getty Images</a></span>
</figcaption>
</figure>
<h2>Upgrading the tools of physics</h2>
<p>Physicists must swing between crafting the mind-bending ideas about reality that make up theories and advancing technologies to the point where new experiments can test those theories. 2021 was a big year for advancing the experimental tools of physics. </p>
<p>First, the world’s largest particle accelerator, the <a href="https://theconversation.com/ten-years-of-large-hadron-collider-discoveries-are-just-the-start-of-decoding-the-universe-102331">Large Hadron Collider at CERN</a>, was shut down and underwent some substantial upgrades. Physicists just restarted the facility in October, and they plan to begin the <a href="https://cerncourier.com/a/protons-back-with-a-splash/">next data collection run in May 2022</a>. The upgrades have boosted the power of the collider so that it can <a href="https://www.universetoday.com/140769/the-large-hadron-collider-has-been-shut-down-and-will-stay-down-for-two-years-while-they-perform-major-upgrades/">produce collisions at 14 TeV</a>, up from the previous limit of 13 TeV. This means the batches of tiny protons that travel in beams around the circular accelerator together carry the same amount of energy as an 800,000-pound (360,000-kilogram) passenger train traveling at 100 mph (160 kph). At these incredible energies, physicists may discover new particles that were too heavy to see at lower energies.</p>
<p>Some other technological advancements were made to help the search for dark matter. Many astrophysicists believe that dark matter particles, which don’t currently fit into the Standard Model, could answer some outstanding questions regarding the way gravity bends around stars – called <a href="https://www.nasa.gov/content/discoveries-highlights-shining-a-light-on-dark-matter">gravitational lensing</a> – as well as the <a href="https://phys.org/news/2019-10-dark-massive-spiral-galaxies-breakneck.html">speed at which stars rotate in spiral galaxies</a>. Projects like the Cryogenic Dark Matter Search have yet to find dark matter particles, but the teams are <a href="https://supercdms.slac.stanford.edu/overview">developing larger and more sensitive detectors</a> to be deployed in the near future. </p>
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<p>Particularly relevant to my work with neutrinos is the development of immense new detectors like <a href="http://www.hyper-k.org/en/">Hyper-Kamiokande</a> and <a href="https://lbnf-dune.fnal.gov/">DUNE</a>. Using these detectors, scientists will hopefully be able to answer questions about a <a href="https://cerncourier.com/a/why-does-cp-violation-matter-to-the-universe/">fundamental asymmetry in how neutrinos oscillate</a>. They will also be used to watch for proton decay, a proposed phenomenon that certain theories predict should occur. </p>
<p>2021 highlighted some of the ways the Standard Model fails to explain every mystery of the universe. But new measurements and new technology are helping physicists move forward in the search for the Theory of Everything.</p><img src="https://counter.theconversation.com/content/173132/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aaron McGowan has received funding in the past from the U.S. Department of Energy. </span></em></p>Physicists know a lot about the most fundamental properties of the universe, but they certainly don’t know everything. 2021 was a big year for physics – what was learned and what’s coming next?Aaron McGowan, Principal Lecturer in Physics and Astronomy, Rochester Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1554332021-02-18T17:31:37Z2021-02-18T17:31:37ZIt’s no Large Hadron Collider, but our new particle accelerator is the size of a large room<figure><img src="https://images.theconversation.com/files/385027/original/file-20210218-20-1451rd2.png?ixlib=rb-1.1.0&rect=7%2C0%2C1552%2C1031&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A prototype of our novel plasma-based particle accelerator</span> <span class="attribution"><span class="source">EuPRAXIA Conceptual Design Report</span></span></figcaption></figure><p>In 2010, when scientists were preparing to smash the first particles together within the Large Hadron Collider (LHC), sections of the media fantasised that the EU-wide experiment might <a href="https://www.forbes.com/sites/startswithabang/2016/03/11/could-the-lhc-make-an-earth-killing-black-hole/">create a black hole</a> that could swallow and destroy our planet. How on Earth, columnists fumed, could scientists justify such a dangerous indulgence in the pursuit of abstract, theoretical knowledge?</p>
<p>But particle accelerators are much more than enormous toys for scientists to play with. They have practical uses too, though their sheer size has, so far, prevented their widespread use. Now, as part of a large-scale European collaboration, my team has <a href="https://doi.org/10.1140/epjst/e2020-000127-8">published a report</a> that explains in detail how a far smaller particle accelerator could be built – closer to the size of a large room, rather than a large city. </p>
<p>Inspired by the technological and scientific know-how of machines like the LHC, our particle accelerator is designed to be as small as possible so it can be put to immediate practical use in industry, in healthcare and in universities.</p>
<h2>Collider scope</h2>
<p>The biggest collider in the world, the LHC, uses particle acceleration to achieve the astonishing speeds at which it collides particles. This system was used to measure the sought-after <a href="https://www.sciencedirect.com/science/article/pii/S037026931200857X">Higgs boson particle</a> – one of the most elusive particles predicted by the Standard Model, which is our current model to describe the structure and operation of the universe.</p>
<p>Less giant and glamorous particle accelerators have been around since the early 1930s, performing useful jobs as well as causing collisions to help our understanding of fundamental science. Accelerated particles are used to generate radioactive materials and strong bursts of radiation, which are crucial for healthcare processes such as radiotherapy, nuclear medicine and CT scans.</p>
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Read more:
<a href="https://theconversation.com/five-ways-particle-accelerators-have-changed-the-world-without-a-higgs-boson-in-sight-54187">Five ways particle accelerators have changed the world (without a Higgs boson in sight)</a>
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<p>The typical downside to accelerators is that they tend to be bulky, complex to run and often prohibitively expensive. The LHC represents a pinnacle of experimental physics, but it is 27 kilometres (17 miles) in circumference and cost <a href="https://home.cern/sites/home.web.cern.ch/files/2018-07/factsandfigures-en_0.pdf">6.5 billion Swiss francs (£5.2 billion)</a> to build and test. The accelerators currently installed in select hospitals are smaller and cheaper, but they still cost tens of millions of pounds, and require 400x400m of space for installation. As such, only large regional hospitals can afford the money and the space to host a radiotherapy department.</p>
<p>Why exactly do accelerators need to be so big? The simple answer is that if they were any smaller, they’d break. Since they’re based on solid materials, ramping up the power too much would tear the system apart, creating a very expensive mess.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large yellow circle drawn over an aerial view of fields" src="https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/385016/original/file-20210218-12-19epl5i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Large Hadron Collider is a vast looped system on the France-Switzerland border.</span>
<span class="attribution"><span class="source">Cern</span></span>
</figcaption>
</figure>
<h2>Need for speed</h2>
<p>We set out to find a way to make smaller, cheaper particle accelerators for use in a wider range of hospitals – from the large and regional to the small and provincial.</p>
<p>Our team worked on the premise that to accelerate particles you actually have two options: either give them a strong boost over a short distance, or lots of small nudges over a long one – which is how the LHC works.</p>
<p>It’s a bit like reaching 100mph in a vehicle: you can either slowly accelerate in a truck over a long period of time, or you can put your foot down in a sports car and get there in a matter of seconds. Conventional accelerators are a bit like trucks: reliable and docile, but slow. We’ve been searching for the sports car alternative.</p>
<p>We found that alternative in plasma. The beauty of plasma is that it’s just composed of an ionised gas: a gas that’s been broken down to its tiniest components. As such, it doesn’t have the same limit on the power that can be applied to it as a solid system. In effect, you can’t break something that is already broken.</p>
<figure class="align-center ">
<img alt="A man holds a clear component in front of his eye. Behind him is a large yellow pipe" src="https://images.theconversation.com/files/385020/original/file-20210218-28-aii8mb.png?ixlib=rb-1.1.0&rect=8%2C5%2C1830%2C1196&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/385020/original/file-20210218-28-aii8mb.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=393&fit=crop&dpr=1 600w, https://images.theconversation.com/files/385020/original/file-20210218-28-aii8mb.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=393&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/385020/original/file-20210218-28-aii8mb.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=393&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/385020/original/file-20210218-28-aii8mb.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=494&fit=crop&dpr=1 754w, https://images.theconversation.com/files/385020/original/file-20210218-28-aii8mb.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=494&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/385020/original/file-20210218-28-aii8mb.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=494&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A researcher holding a section of our novel particle accelerator. Behind is the corresponding section in a traditional accelerator.</span>
<span class="attribution"><span class="source">EuPRAXIA Conceptual Design Report</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>It’s in this sense that plasmas can sustain much higher accelerating powers – up to a thousand times larger than a solid-state accelerator. The higher the power, the shorter time and distance it takes to accelerate particles, and this leads to smaller, cheaper accelerators. </p>
<p>Our accelerator uses powerful lasers to “shake” the plasmas it contains, moving their particles about in a way that creates waves. It’s a little like the wake left behind by a boat (the laser) on a lake (the plasma). Like a surfer, a beam placed on one of these waves can then be pushed forward by it, constantly accelerating. These waves within plasmas are very small (sub-millimetre) and very powerful, which is what allows the overall accelerator to be extremely small.</p>
<h2>Plasma perks</h2>
<p>Plasma-based particle accelerators like ours will need 100 times less space than existing designs, reducing the space required for installation from 400x400m to just 40x40m. The hardware needed to build our accelerator is cheaper to install, run and maintain. Overall, we expect our plasma accelerator to reduce the cost of installing an accelerator in a hospital by a factor of ten.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Four different scanned images of a mouse" src="https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=909&fit=crop&dpr=1 600w, https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=909&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=909&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1142&fit=crop&dpr=1 754w, https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1142&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/385089/original/file-20210218-28-1ia04lk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1142&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A mouse embryo scanned with our machine (left column) and traditional scans (right column).</span>
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<p>Besides these two advantages, our accelerator can perform certain new functions that existing accelerators cannot. For instance, plasma-based accelerators can provide <a href="https://www.youtube.com/watch?v=a8ueGqLPy1I">detailed X-rays of biological samples</a> with <a href="https://www.pnas.org/content/115/25/6335/tab-figures-data">far greater clarity</a> than those that exist today. By providing a better image of the inside of a human body, this could help doctors find cancer at a much earlier stage, dramatically increasing the chance of successfully treating the illness. </p>
<p>The same ultra-high resolution imaging can also help spot the early signs of cracks and defects on machinery, at nanometer scale. Faults related to such defects are regarded as one of the “six big losses” well known to manufacturers. Their early detection by our accelerator could help extend the lifetime of high-precision, high-quality components in heavy industry and manufacturing.</p>
<h2>Accelerator rollout</h2>
<p>The European Strategy Forum on Research Infrastructures is assessing the design report, with a decision expected in summer 2021. If successful, construction of the first two prototypes is expected to be completed by 2030, with access to external users to be granted immediately after.</p>
<p>Several years of interdisciplinary research were needed for us to form the first detailed and realistic design of a machine of this kind. Our plasma accelerator is the most recent example of how obscure, abstract, fundamental physics can enter into our everyday lives – cutting research costs, improving manufacturing and helping to save lives.</p>
<p><em>This article was updated on February 23 2021 to clarify that the EuPRAXIA particle accelerator is designed to perform a different set of tasks than those performed by the Large Hadron Collider.</em></p><img src="https://counter.theconversation.com/content/155433/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gianluca Sarri receives funding from the Engineering and Physical Sciences Research Council (EPSRC) and the Science and Technology Facility Council (STFC). </span></em></p>The compact accelerators are 100 times smaller than traditional ones, and could easily fit inside hospitals and laboratories.Gianluca Sarri, Reader (Associate Professor) at the School of Mathematics and Physics, Queen's University BelfastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1023312018-09-07T17:50:42Z2018-09-07T17:50:42ZTen years of Large Hadron Collider discoveries are just the start of decoding the universe<figure><img src="https://images.theconversation.com/files/235276/original/file-20180906-190642-1uweigo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The activity during a high-energy collision at the CMS control room of the European Organization for Nuclear Research, CERN, at their headquarters outside Geneva, Switzerland. </span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Switzerland-Retooled-Collider/7d495c0dc5a54744b645c260a1017822/9/0">AP Photo</a></span></figcaption></figure><p>Ten years! Ten years since the start of operations for <a href="https://home.cern/topics/large-hadron-collider">the Large Hadron Collider (LHC)</a>, one of the most complex machines ever created. The LHC is the world’s largest particle accelerator, buried 100 meters under the French and Swiss countryside with a 17-mile circumference.</p>
<p>On Sept. 10, 2008, protons, the center of a hydrogen atom, were circulated around the LHC accelerator for the first time. However, the excitement was short-lived because on Sept. 22 an incident occurred that damaged more than 50 of the LHC’s more than 6,000 magnets – which are critical for keeping the protons traveling on their circular path. Repairs took more than a year, but in March 2010 the LHC began colliding protons. The LHC is the crown jewel of <a href="https://home.cern">CERN, the European particle physics laboratory</a> that was founded after World War II as a way to reunite and rebuild science in war-torn Europe. Now <a href="https://voisins.cern/en/cern">scientists from six continents and 100 countries</a> conduct experiments there.</p>
<p>You might be wondering what the LHC does and why it is a big deal. Great questions. The LHC collides two beams of protons together at the highest energies ever achieved in a laboratory. Six experiments located around the 17-mile ring study the results of these collisions with massive detectors built in underground caverns. That’s the what, but why? The goal is to understand the nature of the most basic building blocks of universe and how they interact with each other. This is fundamental science at its most basic.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/235269/original/file-20180906-190647-fzqzvs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/235269/original/file-20180906-190647-fzqzvs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235269/original/file-20180906-190647-fzqzvs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235269/original/file-20180906-190647-fzqzvs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235269/original/file-20180906-190647-fzqzvs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235269/original/file-20180906-190647-fzqzvs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235269/original/file-20180906-190647-fzqzvs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">View of the LHC in its tunnel at CERN (European particle physics laboratory) near Geneva, Switzerland. The LHC is a 27-kilometer-long underground ring of superconducting magnets housed in this pipe-like structure, or cryostat. The cryostat is cooled by liquid helium to keep it at an operating temperature just above absolute zero. It will accelerate two counterrotating beam of protons to an energy of 7 tera-electron volts (TeV) and then bring them to collide head-on. Several detectors are being built around the LHC to detect the various particles produced by the collision.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/SWITZERLAND-CERN-LHC-CRYOGENIC-SYSTEM/b3aef1c7c68a4092a95939b1ca9d36ec/139/0">Martial Trezzini/KEYSTONE/AP Photo</a></span>
</figcaption>
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<p>The LHC has not disappointed. One of the discoveries made with the LHC includes <a href="https://home.cern/topics/higgs-boson">the long sought-after Higgs boson</a>, predicted in 1964 by scientists working to combine theories of two of the fundamental forces of nature.</p>
<p>I work on one of the six LHC experiments – the <a href="https://cms.cern">Compact Muon Solenoid experiment</a> designed to <a href="https://doi.org/10.1088/0954-3899/34/6/S01">discover the Higgs boson and search for signs of previously unknown particles or forces</a>. My institution, <a href="http://www.fsu.edu">Florida State University</a>, joined the Compact Muon Solenoid collaboration in 1994 when I was a young graduate student at another school working on a different experiment at a different laboratory. Planning for the LHC dates back to 1984. The LHC was hard to build and expensive – 10 billion euros – and took 24 years to come to fruition. Now we are celebrating 10 years since the LHC began operating. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=849&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=849&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=849&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1067&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1067&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235273/original/file-20180906-190659-o99p2y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1067&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A view of the Compact Muon Solenoid detector at the European Organization for Nuclear Research (CERN)‘s Large Hadron Collider (LHC) particle accelerator. The core of the Compact Muon Solenoid is the world’s largest superconducting solenoid magnet.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Doomsday-Collider-/628e4c09cab04dafa48ef7d0e870d339/156/0">Martial Trezzini/KEYSTONE/AP Photo</a></span>
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<h2>Discoveries from the LHC</h2>
<p>The most significant discovery to come from the LHC so far is <a href="https://doi.org/10.1016/j.physletb.2012.08.021">the discovery of the Higgs boson</a> on July 4, 2012. The announcement was made at CERN and <a href="http://www.fnal.gov/pub/today/Higgs_Media_Highlights/">captivated a worldwide audience</a>. In fact, my wife and I watched it via webcast on our big screen TV in our living room. Since the announcement was at 3 a.m. Florida time, we went for pancakes at IHOP to celebrate afterwards.</p>
<p>The Higgs boson was the last remaining piece of what we call <a href="https://doi.org/10.1103/RevModPhys.71.S96">the standard model of particle physics</a>. This theory covers all of the known fundamental particles – 17 of them – and three of the four forces through which they interact, although gravity is not yet included. The standard model is an incredibly well-tested theory. Two of the six scientists who developed the part of the standard model that predicts the Higgs boson <a href="https://www.nobelprize.org/prizes/physics/2013/summary/">won the Nobel Prize in 2013</a>.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=682&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=682&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=682&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=857&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=857&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235262/original/file-20180906-190659-1kijrb0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=857&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Higgs boson, sometimes refered to as the ‘God particle,’ was first seen during by experiments at the Large Hadron Collider.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/higgs-boson-what-god-particle-part-171639761?src=gOrKO--a6FdCpbVa-e2fTg-1-27">Designua/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>I am often asked, why do we continue to run experiments, smashing together protons, if we’ve already discovered the Higgs boson? Aren’t we done? Well, there is still lots to be understood. There are a number of questions that the standard model does not answer. For example, studies of galaxies and other large-scale structures in the universe indicate that there is a lot more matter out there than we observe. We call this dark matter since we can’t see it. The most common explanation to date is that <a href="https://doi.org/10.1146/annurev-astro-082708-101659">dark matter is made of an unknown particle</a>. Physicists hope that the LHC may be able to produce this mystery particle and study it. That would be an amazing discovery.</p>
<p>Just last week, the ATLAS and Compact Muon Solenoid collaborations announced <a href="https://arxiv.org/abs/1808.08242">the first observation of the Higgs boson decaying, or breaking apart, into bottom quarks</a>. The Higgs boson decays in many different ways – some rare, some common. The standard model makes predictions about how often each type of decay happens. To fully test the model, we need to observe all of the predicted decays. Our recent observation is in agreement with the standard model – another success.</p>
<h2>More questions, more answers to come</h2>
<p>There are lots of other puzzles in the universe and we may require new theories of physics to explain such phenomena – such as <a href="https://doi.org/10.1103/RevModPhys.76.1">matter/anti-matter asymmetry</a> to explain why the universe has more matter than anti-matter, or the <a href="http://dx.doi.org/10.1590/S0103-97332007000400006">hierarchy problem</a> to understand why gravity is so much weaker than the other forces.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=421&fit=crop&dpr=1 600w, https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=421&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=421&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=529&fit=crop&dpr=1 754w, https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=529&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/235265/original/file-20180906-190650-10btvtr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=529&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Diagram of the standard model of particle physics. There are 13 fundamental particles that make up matter that have now been discovered and four fundamental force carriers.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/diagram-standard-model-particle-physics-12-170480570">Designua/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>But for me, the quest for new, unexplained data is important because every time that physicists think we have it all figured out, nature provides a surprise that leads to a deeper understanding of our world.</p>
<p>The LHC continues to test the standard model of particle physics. Scientists love when theory matches data. But we usually learn more when they don’t. This means we don’t fully understand what is happening. And that, for many of us, is the future goal of the LHC: to discover evidence of something we don’t understand. There are thousands of theories that predict new physics that we have not observed. Which are right? We need a discovery to learn if any are correct.</p>
<p>CERN plans to continue LHC operations for a long time. We are planning <a href="http://dx.doi.org/10.23731/CYRM-2017-004">upgrades to the accelerator and detectors</a> to allow it to run through 2035. It is not clear who will retire first, me or the LHC. Ten years ago, we anxiously awaited the first beams of protons. Now we are busy studying a wealth of data and hope for a surprise that leads us down a new path. Here’s to looking forward to the next 20 years.</p><img src="https://counter.theconversation.com/content/102331/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Todd Adams receives funding from US Department of Energy. </span></em></p>The Large Hadron Collider has generated mind-blowing science in the last decade – including the Higgs boson particle. Why is the LHC so important, and how will physicists use it in the years to come?Todd Adams, Professor of Physics, Florida State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/947002018-05-23T10:39:19Z2018-05-23T10:39:19ZThe Standard Model of particle physics: The absolutely amazing theory of almost everything<figure><img src="https://images.theconversation.com/files/219824/original/file-20180521-14978-36nv6i.jpg?ixlib=rb-1.1.0&rect=174%2C0%2C977%2C649&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">How does our world work on a subatomic level?</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Varsha_ys.jpg">Varsha Y S</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The Standard Model. What a dull name for the most accurate scientific theory known to human beings.</p>
<p>More than a quarter of the Nobel Prizes in physics of the last century are direct inputs to or direct results of the Standard Model. Yet its name suggests that if you can afford a few extra dollars a month you should buy the upgrade. <a href="https://scholar.google.com/citations?user=eQiX0m4AAAAJ&hl=en&oi=ao">As a theoretical physicist</a>, I’d prefer The Absolutely Amazing Theory of Almost Everything. That’s what the Standard Model really is.</p>
<p>Many recall the excitement among scientists and media over the 2012 <a href="https://home.cern/topics/higgs-boson">discovery of the Higgs boson</a>. But that much-ballyhooed event didn’t come out of the blue – it capped a five-decade undefeated streak for the Standard Model. Every fundamental force but gravity is included in it. Every attempt to overturn it to demonstrate in the laboratory that it must be substantially reworked – and there have been many over the past 50 years – has failed. </p>
<p>In short, the <a href="https://home.cern/about/physics/standard-model">Standard Model</a> answers this question: What is everything made of, and how does it hold together?</p>
<h2>The smallest building blocks</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">But these elements can be broken down further.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Periodic_table_vectorial.png">Rubén Vera Koster</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>You know, of course, that the world around us is made of molecules, and molecules are made of atoms. Chemist <a href="https://www.famousscientists.org/dmitri-mendeleev/">Dmitri Mendeleev</a> figured out in the 1860s how to organize all atoms – that is, the elements – into the periodic table that you probably studied in middle school. But there are 118 different chemical elements. There’s antimony, arsenic, aluminum, selenium … and 114 more.</p>
<p>Physicists like things simple. We want to boil things down to their essence, a few basic building blocks. Over a hundred chemical elements is not simple. The ancients believed that everything is made of just five elements – <a href="https://en.wikipedia.org/wiki/Classical_element">earth, water, fire, air and aether</a>. Five is much simpler than 118. It’s also wrong. </p>
<p>By 1932, scientists knew that all those atoms are made of just three particles – neutrons, protons and electrons. The neutrons and protons are bound together tightly into the nucleus. The electrons, thousands of times lighter, whirl around the nucleus at speeds approaching that of light. Physicists <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1918/planck-bio.html">Planck</a>, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html">Bohr</a>, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1933/schrodinger-bio.html">Schroedinger</a>, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1932/heisenberg-bio.html">Heisenberg</a> and friends had invented a new science – <a href="https://en.wikipedia.org/wiki/Quantum_mechanics">quantum mechanics</a> – to explain this motion.</p>
<p>That would have been a satisfying place to stop. Just three particles. Three is even simpler than five. But held together how? The negatively charged electrons and positively charged protons are bound together by <a href="https://en.wikipedia.org/wiki/Electromagnetism">electromagnetism</a>. But the protons are all huddled together in the nucleus and their positive charges should be pushing them powerfully apart. The neutral neutrons can’t help. </p>
<p>What binds these protons and neutrons together? “Divine intervention” a man on a Toronto street corner told me; he had a pamphlet, I could read all about it. But this scenario seemed like a lot of trouble even for a divine being – keeping tabs on every single one of the universe’s 10⁸⁰ protons and neutrons and bending them to its will. </p>
<h2>Expanding the zoo of particles</h2>
<p>Meanwhile, nature cruelly declined to keep its zoo of particles to just three. Really four, because we should count the <a href="https://en.wikipedia.org/wiki/Photon">photon</a>, the particle of light that <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-bio.html">Einstein</a> described. Four grew to five when <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1936/anderson-bio.html">Anderson</a> measured electrons with positive charge – positrons – striking the Earth from outer space. At least <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1933/dirac-bio.html">Dirac</a> had predicted these first anti-matter particles. Five became six when the pion, which <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1949/yukawa-bio.html">Yukawa</a> predicted would hold the nucleus together, was found. </p>
<p>Then came the muon – 200 times heavier than the electron, but otherwise a twin. “Who ordered that?” <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1944/rabi-bio.html">I.I. Rabi</a> quipped. That sums it up. Number seven. Not only not simple, redundant.</p>
<p>By the 1960s there were hundreds of “fundamental” particles. In place of the well-organized periodic table, there were just long lists of baryons (heavy particles like protons and neutrons), mesons (like <a href="https://en.wikipedia.org/wiki/Hideki_Yukawa">Yukawa</a>’s pions) and leptons (light particles like the electron, and the elusive neutrinos) – with no organization and no guiding principles.</p>
<p>Into this breach sidled the Standard Model. It was not an overnight flash of brilliance. No Archimedes leapt out of a bathtub shouting “eureka.” Instead, there was a series of crucial insights by a few key individuals in the mid-1960s that transformed this quagmire into a simple theory, and then five decades of experimental verification and theoretical elaboration. </p>
<p><a href="https://home.cern/about/updates/2014/01/fifty-years-quarks">Quarks</a>. They come in six varieties we call flavors. Like ice cream, except not as tasty. Instead of vanilla, chocolate and so on, we have up, down, strange, charm, bottom and top. In 1964, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1969/gell-mann-bio.html">Gell-Mann</a> and <a href="https://www.macfound.org/fellows/113/">Zweig</a> taught us the recipes: Mix and match any three quarks to get a baryon. Protons are two ups and a down quark bound together; neutrons are two downs and an up. Choose one quark and one antiquark to get a meson. A pion is an up or a down quark bound to an anti-up or an anti-down. All the material of our daily lives is made of just up and down quarks and anti-quarks and electrons.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=536&fit=crop&dpr=1 600w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=536&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=536&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=673&fit=crop&dpr=1 754w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=673&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=673&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Standard Model of elementary particles provides an ingredients list for everything around us.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Standard_Model_From_Fermi_Lab.jpg">Fermi National Accelerator Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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</figure>
<p>Simple. Well, simple-ish, because keeping those quarks bound is a feat. They are tied to one another so tightly that you never ever find a quark or anti-quark on its own. The theory of that binding, and the particles called gluons (chuckle) that are responsible, is called <a href="https://en.wikipedia.org/wiki/Quantum_chromodynamics">quantum chromodynamics</a>. It’s a vital piece of the Standard Model, but mathematically difficult, even posing an unsolved problem of basic mathematics. We physicists do our best to calculate with it, but we’re still learning how.</p>
<p>The other aspect of the Standard Model is “<a href="https://doi.org/10.1103/PhysRevLett.19.1264">A Model of Leptons</a>.” That’s the name of the landmark 1967 paper by <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1979/weinberg-bio.html">Steven Weinberg</a> that pulled together quantum mechanics with the vital pieces of knowledge of how particles interact and organized the two into a single theory. It incorporated the familiar electromagnetism, joined it with what physicists called “the weak force” that causes certain radioactive decays, and explained that they were different aspects of the same force. It incorporated <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/2013/higgs-facts.html">the Higgs mechanism</a> for giving mass to fundamental particles. </p>
<p>Since then, the Standard Model has predicted the results of experiment after experiment, including the discovery of several varieties of quarks and of the <a href="https://en.wikipedia.org/wiki/W_and_Z_bosons">W and Z bosons</a> – heavy particles that are for weak interactions what the photon is for electromagnetism. The possibility that <a href="https://en.wikipedia.org/wiki/Neutrino#Mass">neutrinos aren’t massless</a> was overlooked in the 1960s, but slipped easily into the Standard Model in the 1990s, a few decades late to the party.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">3D view of an event recorded at the CERN particle accelerator showing characteristics expected from the decay of the SM Higgs boson to a pair of photons (dashed yellow lines and green towers).</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:3D_view_of_an_event_recorded_with_the_CMS_detector_in_2012_at_a_proton-proton_centre_of_mass_energy_of_8_TeV.png">McCauley, Thomas; Taylor, Lucas; for the CMS Collaboration CERN</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Discovering the Higgs boson in 2012, long predicted by the Standard Model and long sought after, was a thrill but not a surprise. It was yet another crucial victory for the Standard Model over the dark forces that particle physicists have repeatedly warned loomed over the horizon. Concerned that the Standard Model didn’t adequately embody their expectations of simplicity, worried about its mathematical self-consistency, or looking ahead to the eventual necessity to bring the force of gravity into the fold, physicists have made numerous proposals for theories beyond the Standard Model. These bear exciting names like <a href="https://en.wikipedia.org/wiki/Grand_Unified_Theory">Grand Unified Theories</a>, <a href="https://en.wikipedia.org/wiki/Supersymmetry">Supersymmetry</a>, <a href="https://en.wikipedia.org/wiki/Technicolor_(physics)">Technicolor</a>, and <a href="https://en.wikipedia.org/wiki/String_theory">String Theory</a>. </p>
<p>Sadly, at least for their proponents, beyond-the-Standard-Model theories have not yet successfully predicted any new experimental phenomenon or any experimental discrepancy with the Standard Model.</p>
<p>After five decades, far from requiring an upgrade, the Standard Model is <a href="http://artsci.case.edu/smat50/">worthy of celebration</a> as the Absolutely Amazing Theory of Almost Everything.</p><img src="https://counter.theconversation.com/content/94700/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Glenn Starkman receives funding from the Office of Science of the US Department of Energy. He is affiliated with Case Western Reserve University. </span></em></p>A particle physicist explains just what this keystone theory includes. After 50 years, it’s the best we’ve got to answer what everything in the universe is made of and how it all holds together.Glenn Starkman, Distinguished University Professor of Physics, Case Western Reserve UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/858082017-10-25T13:34:11Z2017-10-25T13:34:11ZDark matter: The mystery substance physics still can’t identify that makes up the majority of our universe<figure><img src="https://images.theconversation.com/files/191475/original/file-20171023-1695-1xeghxr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Map of all matter – most of which is invisible dark matter – between Earth and the edge of the observable universe.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/planck/multimedia/pia16875.html#.We5FQkzMzdc">ESA/NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The past few decades have ushered in an amazing era in the science of cosmology. A diverse array of high-precision measurements has allowed us to reconstruct our universe’s history in remarkable detail.</p>
<p>And when we compare different measurements – of the <a href="http://earthsky.org/space/video-hubble-constant-rate-expansion-universe">expansion rate of the universe</a>, the patterns of light released in the <a href="http://planck.cf.ac.uk/science/cmb">formation of the first atoms</a>, the <a href="https://www.e-education.psu.edu/astro801/content/l10_p6.html">distributions in space of galaxies and galaxy clusters</a> and the <a href="http://w.astro.berkeley.edu/%7Emwhite/darkmatter/bbn.html">abundances of various chemical species</a> – we find that they all tell the same story, and all support the same series of events.</p>
<p>This line of research has, frankly, been more successful than I think we had any right to have hoped. We know more about the origin and history of our universe today than almost anyone a few decades ago would have guessed that we would learn in such a short time.</p>
<p>But despite these very considerable successes, there remains much more to be learned. And in some ways, the discoveries made in recent decades have raised as many new questions as they have answered.</p>
<p>One of the most vexing gets at the heart of what our universe is actually made of. Cosmological observations have determined the <a href="https://doi.org/10.1051/0004-6361/201525830">average density of matter in our universe</a> to very high precision. But this density turns out to be much greater than can be accounted for with ordinary atoms.</p>
<p>After decades of measurements and debate, we are now confident that the overwhelming majority of our universe’s matter – about 84 percent – is not made up of atoms, or of any other known substance. Although we can feel the gravitational pull of this other matter, and clearly tell that it’s there, we simply do not know what it is. This mysterious stuff is invisible, or at least nearly so. For lack of a better name, we call it “dark matter.” But naming something is very different from understanding it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&rect=79%2C517%2C2119%2C1562&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&rect=79%2C517%2C2119%2C1562&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191472/original/file-20171023-1722-1ei7aqm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Astronomers map dark matter indirectly, via its gravitational pull on other objects.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/mission_pages/hubble/science/dark-matter-map.html">NASA, ESA, and D. Coe (NASA JPL/Caltech and STScI)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>For almost as long as we’ve known that dark matter exists, physicists and astronomers have been devising ways to try to learn what it’s made of. They’ve built <a href="https://pandax.sjtu.edu.cn/">ultra-sensitive detectors</a>, <a href="http://lux.brown.edu/LUX_dark_matter/Home.html">deployed in</a> <a href="http://www.xenon1t.org/">deep underground mines</a>, in an effort to measure the gentle impacts of individual dark matter particles colliding with atoms.</p>
<p>They’ve built exotic telescopes – sensitive not to optical light but <a href="https://fermi.gsfc.nasa.gov/">to less familiar gamma rays</a>, <a href="http://www.ams02.org/">cosmic rays</a> and <a href="http://icecube.wisc.edu/">neutrinos</a> – to search for the high-energy radiation that is thought to be generated through the interactions of dark matter particles.</p>
<p>And we have searched for signs of dark matter using incredible machines which accelerate beams of particles – typically protons or electrons – up to the highest speeds possible, and then smash them into one another in an effort to <a href="http://www.tedxnaperville.com/talks/dan-hooper/">convert their energy into matter</a>. The idea is these collisions could create new and exotic substances, perhaps including the kinds of particles that make up the dark matter of our universe.</p>
<p>As recently as a decade ago, most cosmologists – including myself – were reasonably confident that we would soon begin to solve the puzzle of dark matter. After all, there was an ambitious experimental program on the horizon, which we anticipated would enable us to identify the nature of this substance and to begin to measure its properties. This program included the world’s most powerful particle accelerator – <a href="https://home.cern/topics/large-hadron-collider">the Large Hadron Collider</a> – as well as an array of other new experiments and powerful telescopes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191469/original/file-20171023-1717-1lamup8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Experiments at CERN are trying to zero in on dark matter – but so far no dice.</span>
<span class="attribution"><a class="source" href="http://cds.cern.ch/record/2229237">CERN</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>But things did not play out the way that we expected them to. Although these experiments and observations have been carried out as well as or better than we could have hoped, the discoveries did not come.</p>
<p>Over the past 15 years, for example, experiments designed to detect individual particles of dark matter have become a million times more sensitive, and yet no signs of these elusive particles have appeared. And although the Large Hadron Collider has by all technical standards performed beautifully, with the exception of the <a href="https://home.cern/topics/higgs-boson">Higgs boson</a>, no new particles or other phenomena have been discovered.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=902&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=902&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=902&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1133&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1133&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191628/original/file-20171024-30596-1rj833x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1133&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">At Fermilab, the Cryogenic Dark Matter Search uses towers of disks made from silicon and germanium to search for particle interactions from dark matter.</span>
<span class="attribution"><a class="source" href="http://vms.fnal.gov/asset/detail?recid=1783766">Reidar Hahn/Fermilab</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The stubborn elusiveness of dark matter has left many scientists both surprised and confused. We had what seemed like very good reasons to expect particles of dark matter to be discovered by now. And yet the hunt continues, and the mystery deepens.</p>
<p>In many ways, we have only more open questions now than we did a decade or two ago. And at times, it can seem that the more precisely we measure our universe, the less we understand it. Throughout the second half of the 20th century, theoretical particle physicists were often very successful at predicting the kinds of particles that would be discovered as accelerators became increasingly powerful. It was a truly impressive run.</p>
<p>But our prescience seems to have come to an end – the long-predicted particles associated with our favorite and most well-motivated theories have stubbornly refused to appear. Perhaps the discoveries of such particles are right around the corner, and our confidence will soon be restored. But right now, there seems to be little support for such optimism.</p>
<p>In response, droves of physicists are going back to their chalkboards, revisiting and revising their assumptions. With bruised egos and a bit more humility, we are desperately attempting to find a new way to make sense of our world.</p><img src="https://counter.theconversation.com/content/85808/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dan Hooper does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Cosmologists are heading back to their chalkboards as the experiments designed to figure out what this unknown 84 percent of our universe actually is come up empty.Dan Hooper, Associate Scientist in Theoretical Astrophysics at Fermi National Accelerator Laboratory and Associate Professor of Astronomy and Astrophysics, University of ChicagoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/706442016-12-20T05:22:03Z2016-12-20T05:22:03ZAntimatter breakthrough sheds light on matter’s shadowy twin<figure><img src="https://images.theconversation.com/files/150907/original/image-20161220-26712-s4xew.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There's a lot we still don't know about antimatter.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>It is an exciting time to be a physicist, particularly in Australia. In mid-2012, the <a href="https://theconversation.com/cern-discovers-a-higgs-like-particle-let-the-party-and-head-scratching-begin-8036">Higgs boson was discovered at CERN</a>, and <a href="http://international-relations.web.cern.ch/international-relations/nms/australia.html">physicists from Melbourne</a> contributed to the development of the <a href="https://home.cern/about/experiments/atlas">ATLAS detector</a> that participated in the discovery. </p>
<p>Then came the first <a href="https://theconversation.com/gravitational-waves-discovered-the-universe-has-spoken-54237">direct detection of gravitational waves</a> in early 2016, with Australian contributors from the <a href="https://www.adelaide.edu.au/news/news82942.html">University of Adelaide</a>, the <a href="http://www.anu.edu.au/news/all-news/anu-plays-a-key-role-in-discovery-of-gravitational-waves">Australian National University</a> and the <a href="http://www.gravity.uwa.edu.au/">University of Western Australia</a>. </p>
<p>Now, just <a href="http://www.nature.com/news/ephemeral-antimatter-atoms-pinned-down-in-milestone-laser-test-1.21193">reported in Nature</a>, is another breakthrough in fundamental physics, this time concerning antimatter. And this is another area where Australian researchers have been very active.</p>
<p>The researchers at CERN managed to isolate several atoms of antihydrogen – the antimatter analogue of hydrogen – and measure its properties with unprecedented accuracy.</p>
<p>While Australian researchers were not formally part of this experimental program, we have been providing calculations that show how to <a href="http://phys.org/news/2015-05-physicists-ways-antihydrogen-production.html">increase substantially the number of antihydrogen atoms made</a>.</p>
<h2>Mysterious matter</h2>
<p>Why the interest in antihydrogen, or antimatter in general? It turns out that along with <a href="https://theconversation.com/au/topics/dark-energy-328">dark energy</a> and <a href="https://theconversation.com/au/topics/dark-matter-95">dark matter</a>, the existence of antimatter is quite a mystery to physicists. </p>
<p>The biggest puzzle is why there is so much matter in the universe, and so little antimatter. It would have been much easier to explain if there were equal amounts of matter and antimatter in the universe, or none at all. </p>
<p>The <a href="https://theconversation.com/au/topics/standard-model-of-particle-physics-1312">Standard Model</a> predicts equal amounts of antimatter and matter being created by the Big Bang, but in reality there is a tiny amount of antimatter compared to matter. Why is this so? No one knows, and a Nobel Prize awaits whoever solves this problem.</p>
<p>It gets even more interesting, though. As there is no unification between <a href="https://theconversation.com/au/topics/quantum-mechanics-157">quantum mechanics</a> and <a href="https://theconversation.com/au/topics/general-relativity-161">general relativity</a>, we have no reason to believe that antimatter will behave in a gravitational field in the same way as does matter. </p>
<p>This is something that physicists would very much like to test. But to do so, we need to create a substantial quantity of antimatter. </p>
<p>It also needs to be electrically neutral, so that any effect of gravity on the antimatter isn’t overwhelmed by the far more powerful electromagnetic force. Antihydrogen is a great candidate for this experiment because it has no electric charge.</p>
<p>The interest of the Gravitational Behaviour of Antihydrogen at Rest (<a href="http://gbar.web.cern.ch/GBAR/">GBAR</a>) group at CERN is observing how antihydrogen behaves under gravity. If it falls, just like ordinary hydrogen, not much will be learned regarding the asymmetry of matter and antimatter in the universe. On the other hand, if it goes up, the foundation of physics will need a rethink! </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/150908/original/image-20161220-26712-cpn0f4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The ALPHA2 apparatus at CERN is helping to understand antimatter.</span>
<span class="attribution"><span class="source">CERN</span></span>
</figcaption>
</figure>
<h2>Elusive anti-atoms</h2>
<p>Another way to study antimatter is to examine its structure. </p>
<p>We already know a lot about the behaviour of matter, such as the way electrons move between the shells around the nucleus. We have measured the amount of energy required to bump an electron from the innermost, 1 shell, and the next, 2 shell, with startling precision – out to 15 significant figures. </p>
<p>If the same transition can be measured in antihydrogen to a similar level of precision, then perhaps we will gain a clue to matter-antimatter asymmetry for the first time.</p>
<p>In physics, when we perform experiments, the measurements are repeated many times to ensure that the results are statistically significant. This is not so easy when it comes to working with antihydrogen. </p>
<p>When matter and antimatter come together they annihilate, creating a massive amount of energy (as described by Einstein’s famous E=mc² formula). One practical benefit is in positron emission tomography (<a href="https://theconversation.com/the-science-of-medical-imaging-spect-and-pet-14086">PET</a>) scans for cancer detection. </p>
<p>PET uses the annihilation of positrons (antielectrons) with electrons to create gamma rays that we can use to determine the position of the cancer in the body. </p>
<p>In the new experiment at CERN, the number of antihydrogen atoms initially created is around 25,000. But only about a dozen of these were trapped and could be examined closely.</p>
<p>Nevertheless, that was sufficient to measure the 1 shell to 2 shell transition of an electron to an accuracy of 10 significant figures, all of which agree with the ordinary hydrogen case.</p>
<h2>Antimatter downunder</h2>
<p>Though there have not been any surprises thus far, the next goal is to increase substantially the number of trapped antihydrogen atoms so we can form the gravitational and spectroscopic experiments with considerably improved precision. </p>
<p>This is where our research on how to produce more antihydrogen atoms comes in. Antihydrogen is typically made by bringing together positronium – a short-lived bound state of a positron and an electron – together with antiprotons that are chilled to less than a degree above absolute zero. </p>
<p>We showed that if the positronium is initially prepared in a more electrically excited state, as can be routinely done with modern lasers, then the number of antihydrogen atoms created will increase by several orders of magnitude. </p>
<p>This process is currently under development at CERN, and we look forward to seeing one of the longstanding problems in physics – matter-antimmatter asymmetry – being tackled head-on by the teamwork of experimental and theoretical physicists.</p><img src="https://counter.theconversation.com/content/70644/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Igor Bray receives funding from the Australian Research Council. </span></em></p>One of the great mysteries of the universe is why there is so much more matter than antimatter. Now a new experiment is helping us understand the nature of antimatter better than ever before.Igor Bray, Head of Physics, Astronomy and Medical Radiation Science, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/553562016-04-19T14:02:03Z2016-04-19T14:02:03ZBig data has not revolutionised medicine – we need big theory alongside it<figure><img src="https://images.theconversation.com/files/119143/original/image-20160418-1266-fsdhyp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Genomes don't translate easily into an understanding of disease.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=Y32E6C_-CI2e4_ZBJ_97dg&searchterm=dna%20sequence&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=129618455">www.shutterstock.com</a></span></figcaption></figure><p>Science rests on data, of that there can be no doubt. But peer through the hot haze of hype surrounding the use of big data in biology and you will see plenty of cold facts that suggest we need fresh thinking if we are to turn the swelling ocean of “omes” – <a href="https://ghr.nlm.nih.gov/primer/hgp/genome">genomes</a>, <a href="http://www.thehpp.org/">proteomes</a> and <a href="http://www.nature.com/scitable/definition/transcriptome-296">transcriptomes</a> – into new drugs and treatments.</p>
<p>The relatively <a href="http://www.scientificamerican.com/article/revolution-postponed/">meagre returns</a> from the human genome project reflect how DNA sequences do not translate readily into understanding of disease, let alone treatments. The rebranding of “<a href="https://theconversation.com/how-science-is-using-the-genetics-of-disease-to-make-drugs-better-30747">personalised medicine</a>” – the idea that decoding the genome will lead to treatments tailored to the individual – as “precision medicine” reflects the <a href="https://www.elsevier.com/connect/what-is-precision-medicine-and-can-it-work">dawning realisation</a> that using the -omes of groups of people to develop targeted treatments is quite different from using a person’s own genome.</p>
<p>Because we are all ultimately different, the only way to use our genetic information to predict how an individual will react to a drug is if we have a profound understanding of how the body works, so we can model the way that each person will absorb and interact with the drug molecule. This is tough to do right now, so the next best thing is precision medicine, where we look at how genetically similar people react and then assume that a given person will respond in a similar way.</p>
<p>Even the long-held dream that drugs can be routinely designed by knowing the atomic structure of proteins, in order to identify the location in a protein where a drug acts, has <a href="http://pubs.acs.org/doi/abs/10.1021/ci700332k">not been realised</a>.</p>
<p>Most importantly, the fact that “most published research findings are false”, as famously reported by <a href="http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.0020124">John Ioannidis</a>, an epidemiologist from Stanford University, underlines that data is not the same as facts; one critical dataset – the conclusions of peer reviewed studies – is not to be relied on without evidence of good experimental design and rigorous statistical analysis. Yet many now claim that we live in the “data age”. If you count research findings themselves as an important class of data, it is very worrying to find that they are more likely to be false (incorrect) than true.</p>
<p>“There’s no doubt of the impact of big data, which could contribute more than £200 billion to the UK economy alone over five years,” <a href="http://www.parliament.uk/business/committees/committees-a-z/commons-select/science-and-technology-committee/news-parliament-2015/big-data-dilemma-report-published-15-16/">says Roger Highfield</a>, director of external affairs at the Science Museum, London. But “the worship of big data has encouraged some to make the extraordinary claim that this marks the end of theory and the scientific method”.</p>
<h2>Useful but not profound</h2>
<p>The worship of big data downplays many issues, some profound. To make sense of all this data, researchers are using a type of artificial intelligence known as neural networks. But no matter their “depth” and sophistication, they merely fit curves to existing data. They can fail in circumstances beyond the range of the data used to train them. All they can, in effect, say is that “based on the people we have seen and treated before, we expect the patient in front of us now to do this”. </p>
<p>Still, they can be useful. Two decades ago, one of us (Peter) used big data and <a href="http://bit.ly/1SnfV6s">neural networks</a> to predict the thickening times of complex slurries (semi-liquid mixtures) from infrared spectrums of cement powders. But, even though this became a commercial offering, it has not brought us one iota closer to understanding what mechanisms are at play, which is what is needed to design new kinds of cement.</p>
<p>The most profound challenge arises because, in biology, big data is actually tiny relative to the complexity of a cell, organ or body. One needs to know which data is important for a particular objective. Physicists understand this only too well. The discovery of the Higgs boson at CERN’s Large Hadron Collider required petabytes of data; nevertheless, they used theory to guide their search. Nor do we predict tomorrow’s weather by averaging historic records of that day’s weather – mathematical models do a much better job with the help of daily data from satellites. </p>
<p>Some even dream of minting new physical laws by mining data. But the results to date <a href="https://www3.nd.edu/%7Emsen/Teaching/MathMeth/Reading/Lipson2009.pdf">are limited</a> and unconvincing. <a href="http://www.wiley.com/WileyCDA/WileyTitle/productCd-1118027795,miniSiteCd-IEEE2.html">As Edward put it</a>: “Does anyone really believe that data mining could produce the general theory of relativity?”</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/119145/original/image-20160418-1291-jo8d79.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119145/original/image-20160418-1291-jo8d79.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119145/original/image-20160418-1291-jo8d79.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119145/original/image-20160418-1291-jo8d79.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119145/original/image-20160418-1291-jo8d79.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119145/original/image-20160418-1291-jo8d79.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119145/original/image-20160418-1291-jo8d79.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Big data is tiny relative to the complexity of these brain cells.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=rEfzJN1nBF4l4_iMvpcjHg&searchterm=neuron%20cell&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=267094166">www.shutterstock.com</a></span>
</figcaption>
</figure>
<h2>Understand laws of biology</h2>
<p>Many advocates of big data in biology cling to the forlorn hope that we won’t need theory to form our understanding of the basis of health and disease. But trying to forecast a patient’s reaction to a drug based on the mean response of a thousand others is like trying to forecast the weather on a given date by averaging historic records of that day’s weather.</p>
<p>Equally, trying to find new drugs through machine learning based on accessing all known drugs and existing molecular targets is liable to fail because it is based on existing chemical structures and tiny changes in a potential drug can lead to dramatic differences in potency.</p>
<p>We need deeper conceptualisation, but the prevailing view is that the complexities of life do not easily yield to theoretical models. Leading biological and medical journals publish vanishingly little theory-led, let alone purely theoretical, work. Most data provides snapshots of health, whereas the human body is in constant flux. And very few students are trained to model it.</p>
<p>To effectively use the explosion in big data, we need to improve the modelling of biological processes. As one example of the potential, Peter is already <a href="http://pubs.acs.org/doi/pdf/10.1021/acs.jctc.5b00179">reporting results</a> that show how it will soon be possible to take a person’s genetic makeup and – with the help of sophisticated modelling, heavyweight computing and clever statistics – select the right customised drug in a matter of hours. In the longer term, we are also working on virtual humans, so treatments can be initially tested on a person’s digital doppelganger. </p>
<p>But, to realise this dream, we need to divert funding used to gather and process data towards efforts to discern the laws of biology. Yes, big data is important. But we need big theory too.</p><img src="https://counter.theconversation.com/content/55356/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Peter Coveney receives funding from UK Research Councils (EPSRC, MRC), the European Commission, and UCL. </span></em></p><p class="fine-print"><em><span>Edward R Dougherty receives funding from the National Science Foundation, the National Institutes of Health, and the Los Alamos National Laboratory.</span></em></p>Big data is all well and good, but if we want medical breakthroughs, we’ll need big theory too.Peter Coveney, Professor of Physical Chemistry & Director of Centre for Computational Science, UCLEdward R Dougherty, Distinguished professor, Texas A&M UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/544932016-02-12T10:26:32Z2016-02-12T10:26:32ZWhat’s the point of theoretical physics?<figure><img src="https://images.theconversation.com/files/111194/original/image-20160211-29214-2zauf0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>You don’t have to be a scientist to get excited about breakthroughs in theoretical physics. Discoveries such as gravitational waves and <a href="https://theconversation.com/higgs-bosons-decay-confirms-physics-model-works-20882">the Higgs boson</a> can inspire wonder at the complex beauty of the universe no matter how little you really understand them. </p>
<p>But some people will always question why they should care about scientific advances that have no apparent impact on their daily life – and why we spend millions funding them. Sure, it’s amazing that we can study black holes thousands of light years away and that Einstein really was as much of a genius as we thought, but that won’t change the way most people live or work.</p>
<p>Yet the reality is that purely theoretical studies in physics can sometimes lead to <a href="https://theconversation.com/five-ways-particle-accelerators-have-changed-the-world-without-a-higgs-boson-in-sight-54187">amazing changes</a> in our society. In fact, several key pillars on which our modern society rests, from satellite communication to computers, were made possible by investigations that had no obvious application at the time. </p>
<h2>Quantum leap</h2>
<p>Around 100 years ago, <a href="https://theconversation.com/explainer-quantum-physics-570">quantum mechanics</a> was a purely theoretical topic, only developed to understand certain properties of atoms. Its founding fathers such as Werner Heisenberg and Erwin Schrödinger had no applications in mind at all. They were simply driven by the quest to understand what our world is made of. Quantum mechanics states that you cannot observe a system without changing it fundamentally by your observation, and initially its effects to society were of a philosophical and not a practical nature.</p>
<p>But today, quantum mechanics is the basis of our use of all semiconductors in computers and mobile phones. To build a modern semiconductor for use in a computer, you have to understand concepts such as the way electrons behave when atoms are held together in a solid material, something only described accurately by quantum mechanics. Without it, we would have been stuck using computers based on vacuum tubes.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/111195/original/image-20160211-29175-1om523u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/111195/original/image-20160211-29175-1om523u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/111195/original/image-20160211-29175-1om523u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/111195/original/image-20160211-29175-1om523u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/111195/original/image-20160211-29175-1om523u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/111195/original/image-20160211-29175-1om523u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/111195/original/image-20160211-29175-1om523u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">GPS: a relative success.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>At a similar time as the key developments in quantum mechanics, Albert Einstein was attempting to better understand gravity, the dominating force of the universe. Rather than viewing gravity as a force between two bodies, he described it as a curving of space-time around each body, similar to how a rubber sheet will stretch if a heavy ball is placed on top of it. This was Einstein’s <a href="https://theconversation.com/how-einsteins-general-theory-of-relativity-killed-off-common-sense-physics-50042">general theory of relativity</a>. </p>
<p>Today the most common application of this theory is in GPS. To use signals from satellites to pinpoint your location you need to know the precise time the signal leaves the satellite and when it arrives on Earth. Einstein’s theory of general relativity means that the distance of a clock from the Earth’s centre of gravity affects how fast it ticks. And his theory of special relativity means that the speed a clock is moving at also affects its ticking speed.</p>
<p>Without knowing how to adjust the clocks to take account of these effects, we wouldn’t be able to accurately use the satellite signals to determine our position on the ground. Despite his amazing brain, Einstein probably could not have imagined this application a century ago. </p>
<h2>Scientific culture</h2>
<p>Aside from the potential, eventual applications of doing fundamental research, there are also direct financial benefits. Most of the student and post-docs working on big research projects like the Large Hadron Collider, will <a href="https://royalsociety.org/%7E/media/Royal_Society_Content/policy/publications/2010/4294970126.pdf">not stay in academia</a> but move into industry. During their time in fundamental physics, they are educated at the highest existing technical level and then take their expertise into working companies. This is like educating car mechanics in Formula One racing teams.</p>
<p>Despite these direct and indirect benefits, most theoretical physicists have a very different motive for their work. They simply want to improve humanity’s understanding of the universe. While this might not immediately impact everyone’s lives, I believe it is just as important a reason for pursuing fundamental research. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/111199/original/image-20160211-29202-k3uaot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/111199/original/image-20160211-29202-k3uaot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/111199/original/image-20160211-29202-k3uaot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/111199/original/image-20160211-29202-k3uaot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/111199/original/image-20160211-29202-k3uaot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/111199/original/image-20160211-29202-k3uaot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/111199/original/image-20160211-29202-k3uaot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Infinite inspiration.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>This motivation may well have begun when humans first looked up at the night-sky in ancient times. They wanted to understand the world they lived and so spent time watching nature and creating theories about it, many of them involving gods or supernatural beings. Today we have made huge progress in our understanding of both stars and galaxies and, at the other end of the scale, of the tiny fundamental particles from which matter is built.</p>
<p>It somehow seems that every new level of understanding we achieve comes in tandem with new, more fundamental questions. It is never enough to know what we now know. We always want to continue looking behind newly arising curtains. In that respect, I consider fundamental physics a basic part of human culture.</p>
<p>Now we can wait curiously to find out what unforeseen spin-offs that discoveries such as the Higgs boson or gravitational waves might lead to in the long-term future. But we can also look forward to the new insights into the building-blocks of nature that they will bring us and the new questions they will raise.</p><img src="https://counter.theconversation.com/content/54493/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander Lenz receives funding from STFC. </span></em></p>There’s a good reason you should care about the discovery of gravitational waves, even if you don’t understand the science.Alexander Lenz, Deputy director, Institute for Particle Physics Phenomenology, Durham UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/541872016-02-08T14:11:04Z2016-02-08T14:11:04ZFive ways particle accelerators have changed the world (without a Higgs boson in sight)<figure><img src="https://images.theconversation.com/files/110621/original/image-20160208-2608-14wrw0u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Collision course</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/losalamosnatlab/7944152554/in/photolist-bPMwDn-bPMK5M-bATwEq-bPMYb2-bPNeYM-bPMRRg-bPMvZR-bATsJY-bATnbQ-bASTMQ-bATq5E-bPN8Gr-8nuxVG-C3ncbw-m9hxzi-bUnyq9-a375Tj-dWGGaC-d6ZRMu-5RXsXk-9y3eZi-5WhPRd-8tfRob-5svVGs-ehTFV9-ypfh2-7k1Qjt-bhV6oV-aox8xG-bBBhxA-5oH88Q-aiMCe8-9MpCoe-dUtdGT-e3kkGk-apotRr-bWivbZ-aprbVq-aprbWJ-apotEZ-aprbWf-82Ur7X-82Uqgk-aprbY9-uggkkC-aiMC96-5ywu9v-dFcxxd-9SxkNc-6Vj6Kw">Los Alamos National Laboratory/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>The <a href="https://theconversation.com/explainer-how-does-an-experiment-at-the-large-hadron-collider-work-42846">Large Hadron Collider</a> is probably the world’s most famous science experiment. The 27km-long ring-shaped particle accelerator beneath the edge of the Alps grabbed the world’s attention in 2013 when it proved the existence of the Higgs boson particle. This helped <a href="https://theconversation.com/higgs-bosons-decay-confirms-physics-model-works-20882">physicists confirm</a> that one of their key theories about the way the universe worked was correct – a huge step for science. But particle accelerators also have a big impact on our real lives. Even Christmas wouldn’t be the same without them.</p>
<p>Particle accelerators accelerate the tiny building blocks of matter by using electric fields to speed them up to high velocity/energy. These electric fields are the invisible force field created by charged objects, like static electricity or high voltage equipment.</p>
<p>These devices were initially invented to study what happens when particles collide with each other or with targets. These experiments allowed us to understand the particles themselves, the world around us, and nuclear physics (the study of the atomic nucleus). In itself this knowledge has been vital to the development of many technologies such as MRI scanners in hospitals and nuclear power stations.</p>
<p>There are also medium-sized accelerators that produce intense light or neutrons to allow physicists, biologists and pharmacologists to study materials, viruses, proteins and medicines, leading to countless Nobel prizes and new drugs and vaccines. They are even used by chocolate and <a href="http://www.foodonline.com/doc/how-x-ray-inspection-helped-an-ice-cream-maker-improve-food-safety-and-quality-0001">ice cream makers</a> to study how to make the tastiest products by using X-rays to look at the formation of different crystal structures and how to avoiding icy or chalky parts. </p>
<p>However, the most common type of particle accelerators are not the big 27km giants but the small industrial and medical accelerators that are all around us.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/110617/original/image-20160208-2625-1yimal3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/110617/original/image-20160208-2625-1yimal3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=434&fit=crop&dpr=1 600w, https://images.theconversation.com/files/110617/original/image-20160208-2625-1yimal3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=434&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/110617/original/image-20160208-2625-1yimal3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=434&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/110617/original/image-20160208-2625-1yimal3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=545&fit=crop&dpr=1 754w, https://images.theconversation.com/files/110617/original/image-20160208-2625-1yimal3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=545&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/110617/original/image-20160208-2625-1yimal3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=545&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Radiotherapy.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=Bwlb8vrRoZc3hvzKpAiy_g&searchterm=radiotherapy&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=228667765">Shutterstock</a></span>
</figcaption>
</figure>
<h2>1. Treating cancer</h2>
<p>Particle accelerators play a vital role in modern healthcare. The isotopes used in <a href="https://theconversation.com/the-science-of-medical-imaging-spect-and-pet-14086">PET scanners</a> are normally produced in a particle accelerator, and accelerated electrons are fired onto targets to produce X-rays for radiotherapy and imaging. In the UK, the NHS is constructing two special radiotherapy centres at Manchester Christie and the University College London hospitals that <a href="https://theconversation.com/cutting-edge-particle-physics-could-bring-cancer-therapy-home-13765">use protons</a> rather than electrons for radiotherapy, which allow more targeted doses of radiation with less risk to surrounding tissue.</p>
<h2>2. Preventing terrorist attacks</h2>
<p>The same X-ray sources as used in radiotherapy are also commonly used to boost security at ports and airports. The technology can be used to scan cargo, to ensure that nothing is being smuggled into the country. Due to the size of most cargo, a particle accelerator is needed to produce the high energy X-rays that are required. By using two different X-ray energies, we can even distinguish between different materials (similar scanning can also be done using neutrons). A <a href="http://www.dailymail.co.uk/sciencetech/article-3327008/New-scanner-uses-3D-imaging-tubular-X-rays-spot-bombs-drugs.html">new generation</a> of these scanners may also be able to identify emissions from drugs, or explosives when treated with X-rays. </p>
<h2>3. Protecting the environment</h2>
<p>The X-rays from particle accelerators also have the handy side effect of killing bacteria and insects and this has led to them being used for <a href="http://www.emdt.co.uk/article/x-ray-sterilisation-technology-future">sterilising equipment</a> and for treating tobacco, grain or spices to kill any insects, so reducing waste. They can also be used for breaking down nasty elements in <a href="http://www.symmetrymagazine.org/article/october-2009/cleaner-living-through-electrons">waste water</a> or flue gases to protect the environment.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/110627/original/image-20160208-2625-1amqf2u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/110627/original/image-20160208-2625-1amqf2u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/110627/original/image-20160208-2625-1amqf2u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/110627/original/image-20160208-2625-1amqf2u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/110627/original/image-20160208-2625-1amqf2u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/110627/original/image-20160208-2625-1amqf2u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/110627/original/image-20160208-2625-1amqf2u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Blue topaz.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/kohtz/4301851749/in/photolist-7y97DK-cjHsJ-8v6SJ7-8dMiFX-i5y7Ca-6nHpVJ-7aLwtr-6NHX66-7aLwG4-6nHo4q-6S6N7m-6S6NqQ-e3Qps-6nDdVD-6nHpgC-7hHznq-6NN9SA-6NN9iY-7hDBnR-7hDBED-7hHzxd-7eRFPS-7aQmAu-hqvSS-7d9Czz-74uzqF-2HoNxj-2HoPRA-2HjABF-6PvqGA-hqwpa-hqw3a-7fuPh9-hqw6x-hqvZf-hqvWE-hqwhP-hqwej-hqw9h-hqwsb-hqwbL-hqwjW-hqw4w-hqvPW-hqwg2-hqw7Q-hqvVN-hqwnZ-dJzAJd-oX4Xtb">Craig Kohtz/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>4. Making mobile phones</h2>
<p>Electrons or X-rays generated from particle accelerators also have a lot of <a href="http://www.accelerators-for-society.org/industry/index.php?id=8">industrial uses</a>. They can be used to activate certain molecules in paint or composite fibres to make it dry faster, this process – <a href="http://www.sciencedirect.com/science/article/pii/S0168583X05013364">called curing</a> – is commonly used in cereal box printing or making aircraft parts. Without curing, companies would need huge warehouses just for storing things while they dried out. They can also be used to change the <a href="http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/irradiated-gemstones.html">colour of gemstones</a>, for example an accelerator turns the naturally colourless or brown topaz into the nice blue colour normally associated with it. Particle accelerators are also used to implant ions in semiconductors to tailor their behaviour in electronics, such as mobile phone chips.</p>
<h2>5. Saving Christmas</h2>
<p>One common use for particle accelerators is cross-linking, where the particles are used to break polymer chains in a material so they recombine in a stronger configuration. This is commonly used to make the plastic in electrical cables heat-resistant or to make <a href="http://www.symmetrymagazine.org/article/october-2009/accelerator-application-shrink-wrap">shrink wrap </a>for keeping your Christmas turkey fresh. The plastic is stretched and then placed in an electron beam so that when it is heated it shrinks back to its original size. This provides a strong and tight wrapping, protecting your turkey from nasty bacteria.</p><img src="https://counter.theconversation.com/content/54187/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Graeme Burt receives funding from STFC. He works for the Cockcroft Institute of Accelerator Science and Technology and Lancaster University.</span></em></p>Particle accelerators are helping to push forward the frontiers of theoretical physics but they’ve also had more impact on your everyday life than you realise.Graeme Burt, Senior lecturer in engineering, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/506642015-11-19T04:24:48Z2015-11-19T04:24:48ZThe big data challenge and how Africa can benefit<figure><img src="https://images.theconversation.com/files/102326/original/image-20151118-14214-1vxrw3o.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Large Hadron Collider is playing a key role in enabling the collection of big data. </span> <span class="attribution"><span class="source">Supplied</span></span></figcaption></figure><p><a href="https://theconversation.com/explainer-what-is-big-data-13780">Big data</a> has become some sort of celebrity. Everybody talks about it, but it is not clear what it is. To unpack its relevance to society it is important to backtrack a bit to understand why and how it came to be this ubiquitous problem.</p>
<p>Big data is about processing large amounts of data. It is associated with multiplicities of data formats stored somewhere, say in a <a href="http://searchcloudcomputing.techtarget.com/definition/cloud-computing">cloud</a> or in distributed computing systems. </p>
<p>But the ability to generate data systematically outpaces the ability to store it. The amount of data is becoming so big and is produced so fast that it cannot be stored with current technologies in a cost effective way. What happens when big data becomes too big and too fast?</p>
<h2>How fundamental science contributes to society</h2>
<p>The big data problem is yet another example of how the methods and techniques developed by scientists to study nature have had an impact on society. The techno-economic fabric that underlies modern society would be unthinkable without these contributions.</p>
<p>There are numerous examples of how findings intended to probe nature ended up revolutionising life. Big data is intimately intertwined with fundamental science and continues to evolve with it.</p>
<p>Consider just a few examples: what would life be without electricity or electromagnetic waves? Without the fundamental studies of <a href="http://www.phy.pmf.unizg.hr/%7Edpaar/fizicari/xmaxwell.html">Maxwell</a>, <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1925/hertz-bio.html">Hertz</a> and other physicists on the nature of <a href="http://www.merriam-webster.com/dictionary/electromagnetism">electromagnetism</a> we would not have radio, television or other forms of wave mediated communication, for that matter.</p>
<p>Modern electronics is based on materials called <a href="http://dictionary.reference.com/browse/semiconductor">semi-conductors</a>. What would life today be without <a href="http://www.thefreedictionary.com/electronics">electronics</a>? The invention of transistors and eventually of integrated circuits is based entirely on the work scientists have done by thoroughly studying semi-conductors.</p>
<p>Modern medicine relies on countless techniques and applications. These range from x-rays, medical imaging physics and nuclear magnetic resonance to other techniques such as radiation therapeutic and nuclear medicine physics. Modern medicine and research would be unthinkable without techniques that were initially conceived for scientific research purposes.</p>
<h2>How the information age came about</h2>
<p>The big data problem initially emerged as a result of the need for scientists to communicate and exchange data.</p>
<p>At the European laboratory <a href="http://home.cern/">CERN</a> in 1990, internet pioneer <a href="http://www.w3.org/People/Berners-Lee/">Tim Berners-Lee</a> suggested a browser called <a href="http://www.w3.org/People/Berners-Lee/WorldWideWeb.html">WorldWideWeb</a>, leading to the first web server. The internet was born. </p>
<p>The internet has magnified the ability to exchange information and learn, leading to a proliferation of data.</p>
<p>The problem isn’t only about volume. The time lapsing between the generation and processing of information has also been greatly reduced.</p>
<p>The <a href="http://home.cern/topics/large-hadron-collider">Large Hadron Collider</a> has pushed the boundaries of data collection to limits never seen before.</p>
<p>When the project, and its experiments, were being conceived in the late 1980s scientists realised that new concepts and techniques needed to be developed to deal with streams of data that were bigger than had ever been seen before. </p>
<p>It was then that concepts that contributed to cloud and distributed computing were developed.</p>
<p>One of the main tasks of the Large Hadron Collider is to observe and explore the <a href="http://home.cern/topics/higgs-boson">Higgs boson</a>, a particle connected with the generation of mass of fundamental particles, by means of colliding protons at high energy. </p>
<p>The probability of finding a Higgs boson in a high-energy proton-proton collision is extremely small. For this reason it is necessary to collide many protons many times every second. </p>
<p>The Large Hadron Collider produces data flows of the order of petabytes every second. To give an idea of how big a petabyte is, the entire written works of mankind from beginning of written history, in all languages, can be stored in about 50 petabytes. An experiment at the Large Hadron Collider generates that much data in less than one minute.</p>
<p>Only a small fraction of the data produced is stored. But even this has already reached the exabyte scale (one thousand times a petabyte) leading to new challenges in distributed and cloud computing.</p>
<p>The <a href="http://www.ska.ac.za/about/index.php">Square Kilometre Array</a> (SKA) in South Africa will start generating data in the 2020s. SKA will have the processing power of about 100 million PCs. The <a href="https://www.skatelescope.org/">data</a> it collects in a single day would take nearly two million years to play back on an iPod.</p>
<p>This will produce new challenges for the correlation of vast amounts of data.</p>
<h2>Big data and Africa</h2>
<p>The African continent often lags behind the rest of the world when it comes to embracing innovation. Nevertheless big data is increasingly being seen as a solution to tackling poverty on the continent.</p>
<p>The private sector has been the first to get out of the starting blocks.
The bigger African firms are, naturally, more likely to have big data projects. In Nigeria and <a href="http://www.africanbusinessreview.co.za/technology/1783/Big-Data-in-Africa:-IBM-Dissects-a-Developing-Trend-in-a-Developing-Market">Kenya</a> at least 40% of businesses are in the planning stages of a big data project compared with the global average of 51%. Only 24% of medium companies in the two countries are planning big data projects.</p>
<p>Rich rewards can be reaped from harnessing big data. For example, healthcare organisations can benefit from <a href="http://www.hissjournal.com/content/2/1/3">digitising</a>, combining and effectively using big data. This could enable a range of players, from single-physician offices and multi-provider groups to large hospital networks, to deliver better and more effective services. </p>
<p>Grasping the challenge of managing big data could have big economic spin-offs too. With economies becoming more and more sophisticated and complex the amount of data generated increases rapidly. As a result, in order to improve these complex processes it is necessary to process and understand increasing volumes of data. With this labour productivity is enhanced. </p>
<p>But for any of these benefits to become reality, Africa needs specialists who are proficient in big data techniques. Universities on the continent need to start teaching how big data can be used to find solutions to scientific problems. A sophisticated economy requires specialists who are skilled in big data techniques.</p><img src="https://counter.theconversation.com/content/50664/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bruce Mellado receives funding from the DST, NRF and the University of the Witwatersrand. </span></em></p>Big data is about processing large amounts of data. It is often associated with multiplicities of data. But the ability to generate data outpaces the ability to store it.Bruce Mellado, Professor of Physics, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/492992015-11-11T19:21:13Z2015-11-11T19:21:13ZExplainer: what is mass?<figure><img src="https://images.theconversation.com/files/101632/original/image-20151111-9396-18hihtf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You can feel the weight of an object on Earth because of its mass. But what is mass?</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/jeremybrooks/3785305675/">Flickr/Jeremy Brooks </a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>When it comes to electrons, Higgs bosons or photons, they don’t have much going for them. They possess spin, charge, mass and … that’s about it.</p>
<p>Sometimes they only carry a vanishing amount of some of these features at that. So the mass of a particle is an important property to understand, because it goes to the root of fundamental particle physics.</p>
<p>What is mass then, in the sense of its physical meaning? Why do some particles have mass and others don’t? And you may not think this would be important, but the biggest question is: why do particles have mass at all?</p>
<p>To answer those questions, and go well beyond what Albert Einstein knew about mass, let’s dive into particle physics and general relativity. </p>
<h2>The measure of it</h2>
<p>A professor once told me that the best definition of a physical property is its way of measurement. Following this definition, let’s see how we measure mass.</p>
<p>When you step on a scale, like it or not, it registers your weight. This is because the Earth attracts you with the gravitational force. The force between you and the Earth exists because both you and the Earth have mass.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=437&fit=crop&dpr=1 600w, https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=437&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=437&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=549&fit=crop&dpr=1 754w, https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=549&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/101538/original/image-20151111-21232-1ha1uiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=549&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Your weight is a based on your mass on Earth.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/ssicore/3004213582/">Flickr/Stephanie Sicore</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>If you stepped on the same scale on the moon it would register a fraction of your weight on Earth. About one sixth, to be precise. (There has never been a more effective diet plan: lose 83% of your body weight just by flying to the moon.)</p>
<p>Your moon weight is less because the mass of the moon is less than Earth’s mass, and the gravitational force between the moon and you is proportional to the mass of the moon (<em>M</em>) and your mass (<em>m</em>). This is given by the formula <em>F = GMm/(R<sup>2</sup>)</em> where <em>R</em> is the radius of the moon and <em>G</em> is called Newton’s gravitational constant. </p>
<p>Mass is the charge of the gravitational interaction and without it no gravitational force exists. Physicists refer to this manifestation of mass as gravitational mass. </p>
<p>When you open a door, you have to push it with a force, otherwise the door won’t move. This is because the door has mass manifested as inertia, that is, it counteracts you to change the state of its motion.</p>
<p><a href="http://www.livescience.com/46560-newton-second-law.html">Newton’s second law</a> says that the force you need to change the state of motion of an object is proportional to its inertial mass (<em>F = ma</em>). It’s easier to push a light door than a heavy one with the same acceleration. </p>
<h2>Mass unified</h2>
<p>Einstein connected gravitational and inertial mass via his gravitational equivalence principle. The equivalence principle simply says that gravitational and inertial mass are one and the same thing.</p>
<p>This simple statement, however, coupled with the mathematical idea that the equations of physics <a href="https://theconversation.com/from-newton-to-einstein-the-origins-of-general-relativity-50013">should not depend</a> on the reference frame, leads very far. A main consequence of the equivalence principle are Einstein’s gravitational equations. These equations specify how mass curves space and warps time. </p>
<p>The meaning of Einstein’s gravitational equations is simple: mass warps space-time and curved space-time moves mass around. If you have ever seen a coin spiralling down a funnel shaped wishing well, you know what I’m talking about.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/hayvSnT4n9Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>According to Einstein’s geometric picture of gravity, the Earth orbits around the sun because the latter creates a funnel shaped gravitational well in the fabric of space-time and Earth rotates in it just as the coin rotates in the wishing well.</p>
<p>If the sun had no mass, the gravitational well around it wouldn’t exist and Earth would fly straight away. If Earth had no mass, it wouldn’t feel the curvature of the well and would fly away in a straight line. That’s general relativity in a funnel shaped nut-shell.</p>
<p>Einstein knew all this and much more. After all, he wrote the books on relativity – both on special and general. He figured out how mass is connected to gravity and energy.</p>
<p>The first relation is encapsulated by his gravitational field equations, and the second is the widely known <a href="http://science.howstuffworks.com/science-vs-myth/everyday-myths/einstein-formula.htm"><em>E = mc<sup>2</sup></em></a>. Unfortunately, he never had a chance to learn WHY anything has the property of mass. </p>
<h2>There’s more to mass</h2>
<p>Modern fundamental particle physics gave us the answer in 2012 when the <a href="https://theconversation.com/au/topics/higgs-boson">Higgs boson</a> was finally <a href="https://theconversation.com/cern-discovers-a-higgs-like-particle-let-the-party-and-head-scratching-begin-8036">discovered</a>.</p>
<p>The question is fairly important because, as we saw earlier, without mass there’s no gravity. Or is there? Well, actually, there is.</p>
<p>Take a photon, for example. A photon is the quintessence of masslessness. According to our present understanding, one of the deepest fundamental laws of particle physics, called gauge symmetry, prevents any force carrier particles, including photons, from acquiring even the tiniest of mass.</p>
<p>Yet, a photon is attracted by the sun. Observations clearly show that light from a galaxy far far away, positioned exactly behind the sun, can be observed on either side of the sun. The fact that the sun’s gravitational field bends light was used to prove that general relativity was correct in 1919.</p>
<p>Light interacts with gravitational fields because of <em>E = mc<sup>2</sup></em>. This equation tells us that, from the gravitational perspective, energy and mass are equivalent. A photon carries a tiny bit of energy, so it is slightly attracted by the sun. </p>
<p>The fact that energy gravitates is important, because the bulk of mass around us is, in fact, energy. All the visible parts of galaxies and stars are known to be made mostly of hydrogen, which is just protons and electrons.</p>
<p>Earth is made of many different atoms, but those are just made of nucleons (protons and neutrons) and electrons. Electrons are 2,000 times lighter than nucleons, so they bring much less to the table in terms of mass. And remarkably, most of the mass of protons and neutrons is energy stored in glue.</p>
<p>Glue (or gluon, in scientific terms) is the stuff that keeps protons and neutrons together. It is the carrier of the strong force. Binding energy stored in gluons makes up most of the mass of protons, neutrons, hydrogen and any atom for that matter.</p>
<h2>The role of the Higgs boson</h2>
<p>We could stop here, because we’ve understood the origin of most of the visible mass in the universe. Einstein didn’t know where the mass of macroscopic objects came from, but particle physics revealed this late in the 20th century.</p>
<p>There is, however, one more twist in the story. Perhaps the most amazing one. If Einstein had known about it, he would certainly have loved it.</p>
<p>It is the role of the Higgs boson in generating mass. The <a href="https://theconversation.com/explainer-the-higgs-boson-particle-280">Higgs boson</a>, which is the excitation of the Higgs field, is what provides mass at the fundamental level: it lends mass to the elementary particles.</p>
<p>The Higgs story began with a serious problem in particle physics. By the late 20th century it was evident that gauge symmetries, mentioned earlier, are fundamental laws and they forbid any mass of force carriers.</p>
<p>Yet in 1983 massive force carries, the <a href="http://cern-discoveries.web.cern.ch/cern-discoveries/courier/heavylight/heavylight.html">W and Z bosons</a>, were discovered by the Large Electron-Positron (<a href="http://home.cern/about/accelerators/large-electron-positron-collider">LEP</a>) (the predecessor of the Large Hadron Collider (<a href="http://home.cern/topics/large-hadron-collider">LHC</a>)).</p>
<p>This was a serious conundrum: one of the most fundamental laws of nature, gauge invariance was at stake. Giving up gauge invariance would have meant starting particle physics over from scratch.</p>
<p>Amazingly, smart theorists figured out a way to have their cake and eat it too! They introduced the Higgs mechanism, which allows us to preserve gauge symmetries at the fundamental level but break them such that in our particular universe massive W and Z particles are still possible.</p>
<p>This incredible trick won Sheldon Glashow, Abdus Salam, and Steven Weinberg the <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1979/">1979 Nobel Prize in Physics</a>. Besides force carriers, the Higgs mechanism also lends mass to fundamental matter particles, explaining why electrons, neutrinos or quarks have mass.</p>
<p>The contribution of fundamental electron, quark or neutrino mass, however, is negligible compared to the mass generated by glue around us. So does this mean that the Higgs is negligible at the atomic level?</p>
<p>The answer is no! Without the Higgs boson, electrons would have no mass and all atoms would fall apart. Neutrons would not decay, so even atomic nuclei would look very different. Altogether, the universe would be a very-very different place, lacking galaxies, stars and planets. </p>
<h2>And then came the dark stuff</h2>
<p>So, now we know everything about mass, right? Unfortunately not. Only 5% of the mass in the whole universe comes from ordinary matter (the mass of which is understood).</p>
<p>Nearly 70% of the mass of the universe comes from <a href="http://www.space.com/20929-dark-energy.html">dark energy</a> and about 25% from <a href="http://www.space.com/20930-dark-matter.html">dark matter</a>. </p>
<p>Not only do we not have a clue about what kind of mass that is, we don’t even know what the dark sector is composed of. So stay tuned because the story of mass continues, well into the millennium.</p><img src="https://counter.theconversation.com/content/49299/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Csaba Balazs receives funding from the Australian Research Council. </span></em></p>We talk about mass all the time but what is it that actually gives an object mass? And why do some things have mass and others have no mass at all?Csaba Balazs, Associate Professor in Physics, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/490252015-10-15T04:13:25Z2015-10-15T04:13:25ZBenefits of knowing more about neutrinos which pass through our bodies unnoticed<figure><img src="https://images.theconversation.com/files/98365/original/image-20151014-12654-1q4usks.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Neutrinos, we're looking for you! Japan's Super-Kamiokande detector.</span> <span class="attribution"><span class="source">Kamioka Observatory, ICRR (Institute for Cosmic Ray Research), The University of Tokyo</span></span></figcaption></figure><p>The observation that <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/2015/">neutrinos</a> have mass, which led to the 2015 Nobel Prize for Physics being awarded jointly to Japan’s Takaaki Kajita Japan and Canada’s Arthur McDonald, is important for two key reasons. First, it provides a deeper knowledge of the fundamental tenets of nature. Second, as with any discovery, it comes with innovation in science and technology. </p>
<p>While we know of the existence of neutrinos, not much is known about them. Neutrinos exist in huge numbers in the universe. That is why understanding neutrinos is directly relevant to our knowledge of the universe. </p>
<p>Now that it has been established that neutrinos have <a href="http://www.sciencedaily.com/releases/2015/10/151006083633.htm">mass</a>, we have a key to better understanding how mass is distributed in the universe. Neutrinos may also contribute to understanding why the universe is continuously expanding. </p>
<p>It sits on the similar scale as the discovery of the <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/2013/">Higgs boson</a> at the <a href="http://home.web.cern.ch/topics/large-hadron-collider">Large Hadron Collider</a> at European Organisation for Nuclear Research (<a href="http://home.web.cern.ch/about">CERN</a>), and the future discoveries expected from the <a href="http://www.ska.ac.za/about/project.php">Square Kilometre Array</a> (SKA) project. </p>
<p>Any discovery in experimental science is the result of titanic efforts to overcome technological difficulties and challenges. When the neutrino was first <a href="http://www.pbs.org/wnet/hawking/strange/html/neutrinos.html">postulated</a> in 1930, many thought that it would be mission impossible to detect them, let alone to study its properties – such as its mass.</p>
<p>The relentless need to understand nature better forces scientists to innovate with which to push the boundaries of science and technology. The efforts exerted to demonstrate that neutrinos contain mass have bolstered science and technology in <a href="http://www.cbc.ca/news/technology/canadian-s-nobel-prize-in-physics-highlights-why-basic-science-matters-1.3262835">Canada</a> and <a href="http://www.gmanetwork.com/news/lite/story/539768">Japan</a>. South Africa’s <a href="http://mg.co.za/article/2013-11-27-sa-will-feel-economic-benefits-of-ska-says-director-general">support</a> of projects at CERN, the SKA and other efforts already have a similar effect.</p>
<p>Boosting science and technology via large scientific projects brings the added value of human capacity development in high technology that South Africa is in so much need of.</p>
<h2>What are neutrinos?</h2>
<p>Before answering this question we need to backtrack a bit. Matter is made of <a href="http://education.jlab.org/atomtour/">atoms</a>. Atoms are made of positively charged <a href="http://dictionary.reference.com/browse/nuclei">nuclei</a> and negatively charged <a href="http://dictionary.reference.com/browse/electron">electrons</a> travelling very fast around the nuclei. </p>
<p>The electro-magnetic force holds the electrons in orbit around the nuclei because opposite electric charges attract each other. Nuclei are very heavy compared to electrons and are composed of protons and neutrons. </p>
<p>Neutrinos can be thought of cousins of the electrons, only neutral. Neutrinos share some of the properties of the electrons – for instance, the spin. There is one type of neutrino coupled to the electron, which is called electron neutrino. The electron has an anti-particle, the positron, which has positive electric charge. There is also an electron anti-neutrino.</p>
<p>In nature there are other charged particles that are similar to the electron, which are called muons and taus. These are heavier than the electron. The muons and taus also have two other types of neutrinos respectively. In total we are aware of three types of neutrinos (electron, muon, and tau) and their anti-particles.</p>
<h2>Why are neutrinos elusive?</h2>
<p>Neutrinos do not have electric charge. Therefore, they do not get repelled or attracted to other charged particles in nature. They interact very weakly with matter so they very rarely leave a trace. </p>
<p>Vast amounts of neutrinos <a href="http://timeblimp.com/?page_id=1033">pass through us</a> every day, but we do not feel them because neutrinos hardly ever interact with the atoms that make up our bodies.</p>
<p>Most of the neutrinos that pass through earth come from the sun and are produced by nuclear fusion. These are called solar neutrinos. The other neutrinos are produced as a result of the collision of cosmic particles with the Earth’s atmosphere. These are called atmospheric neutrinos.</p>
<h2>How can we tell that neutrinos have mass?</h2>
<p>There are three types of neutrinos. If neutrinos were massless then they would travel forever unencumbered. If neutrinos have mass then, as they travel, they gradually “disappear” to become a different type of neutrino. </p>
<p>This is referred to as neutrino oscillation and it is a quantum mechanical effect. </p>
<p>For instance, the Sun creates electron neutrinos. By the time neutrinos reach Earth we only observe about one-third of the emitted neutrinos. The remaining two-thirds of the electron neutrinos becomes muon and tau neutrinos. Through this process, it is directly demonstrated that neutrinos have mass.</p>
<h2>Decades of research pay off</h2>
<p>Neutrinos were put forward in 1930 as a means to explain missing energy from a certain type of nuclear reactions. It was not until 1956 that neutrinos were detected unequivocally in laboratory conditions, for which a <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1995/press.html">Nobel Prize in Physics</a> was awarded in 1995. </p>
<p>Scientists from all over the world have not stopped investigating the nature of these elusive particles. Neutrinos were known to be neutral and assumed to be massless. It was not until the late 1990s and early 2000s that experimental techniques became available in order to elucidate if neutrinos have mass. </p>
<p>The latter signifies a major discovery in physics, leading to a Nobel Prize in Physics in 2015. The fact of the matter is that to date we do not really know how neutrinos acquire mass. Unravelling this mystery may lead to other groundbreaking discoveries.</p><img src="https://counter.theconversation.com/content/49025/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bruce Mellado receives funding from the DST, the NRF, Wits research office.</span></em></p>The Nobel Prize-winning research on neutrinos is expected to push the boundaries of science and technology.Bruce Mellado, Professor of Physics, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/447212015-07-15T12:57:00Z2015-07-15T12:57:00ZHere’s what you need to know about the Large Hadron Collider’s latest discovery: pentaquarks<figure><img src="https://images.theconversation.com/files/88494/original/image-20150715-17815-1pe2ckw.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">CERN</span></span></figcaption></figure><p>The Large Hadron Collider, famous for finding the Higgs boson, has now revealed another new and rather unusual particle. Teams at the LHC, the world’s largest particle accelerator, <a href="https://theconversation.com/large-hadron-collider-is-back-to-change-our-understanding-of-the-universe-again-42775">recently began</a> a second <a href="https://theconversation.com/explainer-how-does-an-experiment-at-the-large-hadron-collider-work-42846">run of experiments</a> using far more energy than the ones that found the Higgs particle <a href="https://theconversation.com/cern-discovers-a-higgs-like-particle-let-the-party-and-head-scratching-begin-8036">back in 2012</a>. But another of the groups, LHCb, have also been sifting through its data from the billions of particle collisions of the first run of the LHC, and now think they’ve <a href="http://arxiv.org/abs/1507.03414">spotted something new</a>: pentaquarks.</p>
<p>Pentaquarks are an exotic form of matter first predicted <a href="http://journals.aps.org/prd/abstract/10.1103/PhysRevD.20.748">back in 1979</a>. Everything around us is made of atoms, which are mode of a cloud of electrons orbiting a heavy nucleus made of protons and neutrons. But <a href="http://www.sciencedirect.com/science/article/pii/S0031916364920013">since the 1960s</a>, we’ve also known that protons and neutrons are made up of even smaller <a href="https://theconversation.com/explainer-quarks-12003">particles named “quarks</a>”, held together by something called the “strong force”, the strongest known force in nature in fact.</p>
<p><a href="http://wwwphy.princeton.edu/%7Ekirkmcd/examples/EP/breidenbach_prl_23_935_69.pdf">Experiments in 1968</a> provided the evidence for the quark model. If protons are hit hard enough, the strong force can be overcome and the proton smashed apart. The quark model actually explains the existence of more than 100 particles, all known as “hadrons” (as in Large Hadron Collider) and made up of different combinations of quarks. For example the proton is made of three quarks.</p>
<p>All hadrons seem to be made up of combinations of either two or three quarks, but there is no obvious reason more quarks could not stick together to form other types of hadron. <a href="https://inis.iaea.org/search/search.aspx?orig_q=RN:190196">Enter the pentaquark</a>: five quarks bound together to form a new type of particle. But until now, nobody knew for sure if pentaquarks actually existed – and, although there have been several discoveries claimed in the last 20 years, none has stood the test of time.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/88496/original/image-20150715-17785-klc9jf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/88496/original/image-20150715-17785-klc9jf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/88496/original/image-20150715-17785-klc9jf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/88496/original/image-20150715-17785-klc9jf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/88496/original/image-20150715-17785-klc9jf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/88496/original/image-20150715-17785-klc9jf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/88496/original/image-20150715-17785-klc9jf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The intricate dance of the J/psi and the proton.</span>
<span class="attribution"><span class="source">CERN</span></span>
</figcaption>
</figure>
<p>Pentaquarks are incredibly difficult to see; they are very rare and very unstable. This means that if it is possible to stick five quarks together, they won’t stay together for very long. The team on the LHCb experiment made their discovery by looking in detail at other exotic hadrons produced in the collisions and they way these break apart. In particular, they looked for the Lambda<sub>b</sub> particle, which can decay into thee other hadrons: a Kaon, a J/psi, and a proton.</p>
<p>The J/psi is made of two quarks and the proton is made of three. The scientists discovered that for a short period of time these five quarks were bound together in a single particle: a pentaquark. In fact, through detailed analysis of the data, they actually discovered two pentaquarks and have given them the catchy names Pc(4450)+ and Pc(4380)+.</p>
<h2>Why is this important?</h2>
<p>The discovery answers a decades-old question in particle physics and highlights another part of the mission of the LHC. Discoveries of new fundamental particles such as the Higgs boson tell us something completely new about the universe. But discoveries like pentaquarks give us a more complete understanding of the rich possibilities that lie in the universe we already know.</p>
<p>By developing this understanding, we may get some hints about how the universe developed after the Big Bang and how we’ve ended up with protons and neutrons instead of pentaquarks making up everyday matter. </p>
<p>With the LHC now colliding protons at almost twice the energy, scientists are ready to tackle some of the <a href="https://theconversation.com/large-hadron-collider-is-back-to-change-our-understanding-of-the-universe-again-42775">other open questions</a> in <a href="https://theconversation.com/beyond-the-higgs-boson-five-reasons-physics-is-still-interesting-20380">particle physics</a>. One of the main targets with the new data is <a href="https://theconversation.com/shedding-new-light-on-the-search-for-the-invisible-dark-matter-40083">Dark Matter</a>, a strange particle which seems to be all around the universe, but has never been seen. Testing the current understanding of quarks, the strong force and all the known particles at this new energy is an essential step towards making such discoveries.</p><img src="https://counter.theconversation.com/content/44721/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gavin Hesketh is a lecturer in particle physics at University College London, and a member of the ATLAS Collaboration at CERN. He receives funding from the Science and Technology Facilities Council, and the Royal Society.</span></em></p>The latest data from the particle accelerator that found the Higgs Boson has confirmed another of our theories about how the universe works.Gavin Hesketh, Lecturer in Particle Physics, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/428462015-06-05T15:34:31Z2015-06-05T15:34:31ZExplainer: how does an experiment at the Large Hadron Collider work?<figure><img src="https://images.theconversation.com/files/84113/original/image-20150605-8677-1ykfc31.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Supersize symmetry</span> <span class="attribution"><span class="source">Maximilien Brice/CERN</span></span></figcaption></figure><p>It’s not every day my Twitter feed is full of people talking about flat-tops, squeezing and injections, but then Wednesday 3 June was not an average day for the Large Hadron Collider.</p>
<p>The LHC is the world’s largest particle accelerator and lies in a tunnel below <a href="http://home.web.cern.ch">CERN</a>, the European physics lab just outside Geneva. And on Wednesday it was restarted after two year break for repairs and upgrades, ready to push our understanding of the universe to new limits. </p>
<p>As my fellow physicists crowded into the control rooms and waited for things to get underway, I was at a workshop in France. But I was able to follow the <a href="http://run2-13tev.web.cern.ch">switch-on online</a>. Here’s how things went down.</p>
<p><strong>8.09am. Injection: Billions of protons are loaded into the LHC.</strong></p>
<p>The LHC is a ring roughly 28km around that accelerates protons almost to the speed of light before colliding them head on. Protons are particles found in the atomic nucleus, roughly one thousand-million-millionth of a metre in size.</p>
<p>They are easiest to get from hydrogen, the simplest atom with just one electron orbiting one proton. The LHC starts with a bottle of hydrogen gas, which is sent through an electric field to strip away the electrons, leaving just the protons. Electric and magnetic fields are the key to a particle accelerator: because protons are positively charged, they accelerate when in an electric field and bend in a circle in a magnetic field. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/84109/original/image-20150605-8725-9xav1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/84109/original/image-20150605-8725-9xav1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/84109/original/image-20150605-8725-9xav1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/84109/original/image-20150605-8725-9xav1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/84109/original/image-20150605-8725-9xav1g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/84109/original/image-20150605-8725-9xav1g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/84109/original/image-20150605-8725-9xav1g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Big data.</span>
<span class="attribution"><span class="source">M.Brice/CERN</span></span>
</figcaption>
</figure>
<p><strong>9.45am. Ramp: Once the LHC is fully loaded, its two proton beams are slowly accelerated up to collision energy, now a world-record 6.5TeV per beam.</strong></p>
<p>Accelerating billions of protons to close to the speed of light, directing them all the way around the LHC, and then colliding them head-on, is a delicate balancing act performed by high voltage equipment and giant magnets. This is an amazing technical achievement. Indeed one of the main applications of particle physics research is in the industrial applications of the technology it develops along the way, from proton therapy cancer treatment to the <a href="http://home.web.cern.ch/topics/birth-web">world wide web</a>.</p>
<p>But for me, the excitement is in the science: the LHC is exploring the universe at the smallest scales. Everything we have learned so far is formulated in the <a href="http://home.web.cern.ch/about/physics/standard-model">Standard Model</a>, a theory which describes the universe made of tiny particles, and gives the rules for how these particles behave. By smashing some of these particles together at high energy, we are able to test these rules and make new discoveries.</p>
<p>The LHC “Run 1” (2010-2013) provided enough data to test the Standard Model to new levels of precision and discover the <a href="https://theconversation.com/definitely-maybe-evidence-grows-for-positive-id-of-higgs-boson-12790">Higgs boson</a>. This particle was predicted in the 1960s and plays a central role in the Standard Model. But it was almost 50 years before we had a machine powerful enough to discover it. As well as high energy, it needed lots of data: the Higgs boson is a rare thing, and fewer than one in a billion collisions at the LHC produce one.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/84110/original/image-20150605-8697-1094eps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/84110/original/image-20150605-8697-1094eps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/84110/original/image-20150605-8697-1094eps.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/84110/original/image-20150605-8697-1094eps.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/84110/original/image-20150605-8697-1094eps.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/84110/original/image-20150605-8697-1094eps.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/84110/original/image-20150605-8697-1094eps.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tense moments.</span>
<span class="attribution"><span class="source">Laurent Egli/CERN</span></span>
</figcaption>
</figure>
<p><strong>10.12am. Flat top: Beam energy levels off after reaching the target.</strong></p>
<p>These were tense moments for the CERN team on Wednesday. The LHC was operating at the <a href="https://theconversation.com/large-hadron-collider-is-back-to-change-our-understanding-of-the-universe-again-42775">highest energy ever</a> achieved in a particle accelerator. “Run 2” will collide protons at 60% higher energies than Run 1 by pushing the magnets and accelerators to the limit. We hope this extra reach will allow us to tackle some of the big questions in particle physics.</p>
<p>One of the main topics is <a href="http://home.web.cern.ch/about/physics/dark-matter">dark matter</a>. This seems to be a new type of particle spread through the entire universe. And with the LHC Run 2 we hope to make it in the lab for the first time. But if the Higgs boson is rare, dark matter is even rarer, and we will need to sort through a lot of collisions before having a hope of finding it.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/84111/original/image-20150605-8725-szj84l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/84111/original/image-20150605-8725-szj84l.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=309&fit=crop&dpr=1 600w, https://images.theconversation.com/files/84111/original/image-20150605-8725-szj84l.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=309&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/84111/original/image-20150605-8725-szj84l.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=309&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/84111/original/image-20150605-8725-szj84l.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=388&fit=crop&dpr=1 754w, https://images.theconversation.com/files/84111/original/image-20150605-8725-szj84l.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=388&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/84111/original/image-20150605-8725-szj84l.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=388&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Worlds collide.</span>
<span class="attribution"><span class="source">CMS/CERN</span></span>
</figcaption>
</figure>
<p><strong>10.17am. Squeeze: The beams are fine-tuned, and focused at the four points around the LHC where they cross, and the experiments will record the collisions</strong></p>
<p>Almost there. The experiments now need to wait for the all-clear before they can start recording, and we begin studying things that have never been seen before. Still, many of the collisions will not be interesting, as the protons just smash apart without doing anything exciting.</p>
<p>To make matters worse, the rare new particles we are looking for also tend to be very unstable, and decay too quickly to be seen directly. So the job of the experiments is to measure whatever particles do come out of a collision and try to reconstruct what happened, looking for evidence of something unusual.</p>
<p>As well as dark matter, there are many other ideas to test, such as <a href="http://home.web.cern.ch/about/physics/supersymmetry">supersymmetry</a>, new gauge bosons, quantum black holes and heavy neutrinos, all of which we could reconstruct from the LHC collisions. Part of the joy and pain of science is that a <a href="https://theconversation.com/is-this-the-end-of-particle-physics-as-we-know-it-lets-hope-not-42849">new discovery</a> could come in a matter of days, or a matter of years.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/84107/original/image-20150605-8674-1xscz2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/84107/original/image-20150605-8674-1xscz2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/84107/original/image-20150605-8674-1xscz2w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/84107/original/image-20150605-8674-1xscz2w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/84107/original/image-20150605-8674-1xscz2w.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/84107/original/image-20150605-8674-1xscz2w.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/84107/original/image-20150605-8674-1xscz2w.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Champagne flowing.</span>
<span class="attribution"><span class="source">Mike Struik/CERN</span></span>
</figcaption>
</figure>
<p><strong>10.43am. Stable beams: The LHC is now running smoothly, the beams are behaving as expected, and the experiments can start recording data.</strong></p>
<p>Run 2 has begun! Champagne is flowing at CERN. Now the attention moves to analysing the new data, and it’s time for the rest of us to get back to work.</p><img src="https://counter.theconversation.com/content/42846/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gavin Hesketh receives funding from The Royal Society and STFC.</span></em></p>Running the world’s largest particle accelerator requires a lot of energy, but it could reveal the secrets of the universe.Gavin Hesketh, Lecturer in Particle Physics, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/427752015-06-03T14:14:14Z2015-06-03T14:14:14ZLarge Hadron Collider is back to change our understanding of the universe … again<p>The Large Hadron Collider (LHC) has just begun smashing particles together at higher energies than ever before. This marks the start of the second run of the world’s largest physics experiment, the huge particle accelerator that sits beneath the Alps and in 2012 was used to prove the existence of the <a href="https://theconversation.com/definitely-maybe-evidence-grows-for-positive-id-of-higgs-boson-12790">Higgs boson</a>.</p>
<p>Now, after more than two years’ work <a href="https://theconversation.com/goodbye-for-a-while-to-the-large-hadron-collider-12238">upgrading the accelerator</a> systems and the particle detectors (and more years of preparation before that), the team at research group CERN are ready to start using the LHC to answer more questions about how the universe works.</p>
<p>The goal is to explain the missing pieces in our understanding of fundamental physics. One example is the nature of the so-called <a href="http://home.web.cern.ch/about/physics/dark-matter">dark matter</a> that scientists say we can’t see directly but that dominates the universe. Another is the imbalance between matter and antimatter in the present-day universe. Our current theories suggest there would have been almost exactly equal amounts of matter and antimatter in the early universe. But somehow the antimatter decayed, allowing the universe that we know made entirely of matter to emerge.</p>
<p>Physicists have proposed a range of theories, <a href="http://home.web.cern.ch/about/physics/supersymmetry">such as “supersymmetry”</a>, to answer these questions and that also predict the existence of new particles and subtle changes to the behaviour of known particles. By colliding particles at energies measured at 13 teraelectronvolts, researchers may also find evidence of the hidden extra dimensions that feature in many theories. Or it could show that the Higgs boson, the particle associated with giving mass to the other particles that make up matter, is one of a whole family of related particles.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/83813/original/image-20150603-2963-6ok9uw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/83813/original/image-20150603-2963-6ok9uw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/83813/original/image-20150603-2963-6ok9uw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/83813/original/image-20150603-2963-6ok9uw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/83813/original/image-20150603-2963-6ok9uw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/83813/original/image-20150603-2963-6ok9uw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/83813/original/image-20150603-2963-6ok9uw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Energy levels up.</span>
<span class="attribution"><span class="source">M Brice/CERN</span></span>
</figcaption>
</figure>
<p>The significance of almost doubling the energy at which particles are fired around the LHC is that the resulting collisions should produce new particles that were inaccessible before. Rarer processes should also become more frequent and so easier to distinguish from the approximately 600m “ordinary” collisions that occur in each experiment each second. And the rate at which Higgs bosons are produced should increase, allowing researchers to determine their true nature.</p>
<p>There are several different experiments scheduled for the higher-energy LHC. My team at the University of Lancaster is part of the <a href="http://atlas.ch">ATLAS experiment</a> and we will be looking studying how the Higgs boson decays into a particle called the tau, a heavier version of the electron. We will be seeing if the decay exhibits what is called <a href="http://cerncourier.com/cws/article/cern/28092">CP violation</a>, a process that distinguishes between matter and antimatter and might help explain the matter-antimatter imbalance.</p>
<p>The improvements to the ATLAS detector for measuring the paths of the particles produced by collisions and the points where they decay mean we in Lancaster will be able to make really precise measurements of CP violation and particle lifetimes in more conventional particles. The extremely large samples of the relevant decays will also contribute to the high precision required to see the influence of any new physics effects such as supersymmetry.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/83812/original/image-20150603-2966-1rs9yi0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/83812/original/image-20150603-2966-1rs9yi0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=309&fit=crop&dpr=1 600w, https://images.theconversation.com/files/83812/original/image-20150603-2966-1rs9yi0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=309&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/83812/original/image-20150603-2966-1rs9yi0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=309&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/83812/original/image-20150603-2966-1rs9yi0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=388&fit=crop&dpr=1 754w, https://images.theconversation.com/files/83812/original/image-20150603-2966-1rs9yi0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=388&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/83812/original/image-20150603-2966-1rs9yi0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=388&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Smashing job.</span>
<span class="attribution"><span class="source">CMS/CERN</span></span>
</figcaption>
</figure>
<p>We will also be looking for other new particles, particularly those that decay into two “jets” of ordinary particles. This is really important for understanding how often you get double collisions between the particles inside the protons. The energy signature from these double collisions can mimic some of the effects predicted by new theories. So we need to understand the collisions before we can claim them as evidence for those theories. </p>
<p>The two year period during which the LHC was offline was an intensely busy time for the accelerator and detector teams. But the work will now intensify at major analysis centres such as Lancaster to extract the relevant results from the large volumes of data the LHC is producing. For the young physicists doing their PhD studies or in their first research positions and the older hands directing them, this is the most exciting time when the work all comes together.</p>
<p>What will be found is unknown – and an unexpected finding could transform our whole programme of work. Whatever nature reveals, it will be interesting and potentially could profoundly change our view of the fundamental workings of the universe.</p><img src="https://counter.theconversation.com/content/42775/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Jones receives funding from STFC.</span></em></p>CERN’s huge particle accelerator has been switched back on after a two-year upgrade to continue its search for answers.Roger Jones, Professor of Physics, Head of Department, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/386642015-03-11T17:56:27Z2015-03-11T17:56:27ZWhat will we find next inside the Large Hadron Collider?<figure><img src="https://images.theconversation.com/files/74513/original/image-20150311-24209-1s37umw.jpg?ixlib=rb-1.1.0&rect=75%2C0%2C810%2C612&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What lies within?</span> <span class="attribution"><span class="source">Maximilien Brice/CERN</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>The Large Hadron Collider, the world’s largest scientific experiment, is due to restart this month <a href="http://www.bbc.co.uk/news/science-environment-21421460">after two years of downtime</a> for maintenance and upgrading. There’s no doubt that having played its role in the discovery of the Higgs boson in 2012, what the media christened the “God particle”, expectations for what the <a href="http://home.web.cern.ch/topics/large-hadron-collider">27km particle accelerator</a> at CERN could achieve this time have certainly been set high.</p>
<p>The <a href="http://home.web.cern.ch/topics/higgs-boson">Higgs boson</a> is a possible explanation for the origin of mass, something predicted in 1964 by Peter Higgs and several other physicists, and the discovery of which led to the award of <a href="https://theconversation.com/nobel-prize-in-physics-goes-to-discovery-of-the-higgs-boson-19014">a Nobel Prize for physics</a> for Higgs and François Englert in 2013.</p>
<p>So why did it take so long to discover it? As Einstein showed in his mass-energy equivalence (E=MC<sup>2),</sup> the mass of a particle is a measure of its energy content. If a particle is more massive, it has a greater energy content, and conversely to create a massive particle requires a great deal of energy. So simply put, it wasn’t until the Large Hadron Collider (LHC) was capable of colliding beams of protons with sufficient energy that the Higgs Boson could be created with its mass of 126 billion electron volts (<a href="http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ev.html">gigaelectronvolts</a>, or GeV). In particle physics it is usual to give masses in terms of energy, and while 126GeV is equivalent to only 2.24x1025kg, this mass is about 127 times larger than a single proton.</p>
<p>So the intention is that following a two-year upgrade the LHC’s new, more powerful electromagnets will be sufficient to accelerate two beams of protons to 6.5 trillion electron volts (teraelectronvolts, or TeV), increasing the potential collision energy from 8TeV in 2012 to 13TeV. And with greater collision energy comes the possibility of creating and detecting new particles of even greater mass. The expectation is that the LHC’s experiments could uncover new particles known as <a href="http://home.web.cern.ch/about/physics/z-boson">Z particles</a>, new Higgs bosons, and even <a href="http://home.web.cern.ch/about/physics/dark-matter">particles of dark matter</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=465&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=465&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=465&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=584&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=584&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74517/original/image-20150311-24168-1m2cvgi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=584&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A map of subatomic particles, known and hypothesised.</span>
<span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/File:Standard_Model_of_Elementary_Particles.svg">MissMJ</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>From Higgs to Z</h2>
<p>Discovered at CERN in 1983, the Z particle is a force carrier – a particle that carries one of the <a href="http://csep10.phys.utk.edu/astr162/lect/cosmology/forces.html">four fundamental forces</a> of nature: the gravitational, electromagnetic, strong and weak forces. The Z particle <a href="http://www.livescience.com/49254-weak-force.html">carries the weak force</a>, which is implicated in subatomic reactions. A related, theorised particle that could be next to be discovered is the <a href="http://press.web.cern.ch/backgrounders/w-prime-and-z-prime">Z prime particle</a>, or Z’. This would help our understanding of gravitons, the carriers of the gravitational force that are theorised but have not yet been detected.</p>
<p>Taking the constituents of the universe as a whole, we have a good understanding of about 5% of it. The remaining 95% is made up of <a href="http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/">about 68% dark energy and 27% dark matter</a>. With a little over 84% of the universe’s mass being dark – not detectable by any known means – if the LHC can in some way shed some light on the nature of this matter it will move our understanding of the universe forward.</p>
<p>With an upgraded LHC able to provide higher collision energies and the possibility of creating new particles – whether those currently theorised or not – it will have a significant impact on our fundamental understanding of the laws of nature and the accepted model that is used to try and explain them.</p>
<p>Some may point to the cost of the LHC upgrade, <a href="http://www.bbc.co.uk/news/science-environment-21941666">estimated at around £70m</a>, as a cost beyond the public purse in these cash-strapped times of austerity. But the possibilities for what it can add to our understanding of the world cannot be ignored either, nor the benefits they might have in other areas, for example medical imaging. Considering how regularly sums far larger than £70m of taxpayers’ money are squandered, CERN’s role as a global educational tool for physicists, mathematicians and engineers must be considered excellent value for money.</p><img src="https://counter.theconversation.com/content/38664/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gren Ireson receives funding from the European Union and Particle Physics and Astronomy Research Council.</span></em></p>Ticking off subatomic particles one by one, now let’s see what an LHC upgrade will do.Gren Ireson, Professor of physics, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/376382015-02-24T19:30:25Z2015-02-24T19:30:25ZThe LHC is back and it’s ready to probe the limits of matter<figure><img src="https://images.theconversation.com/files/72728/original/image-20150223-21887-hkve6j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A 3D artist has dissected the LHC in this composite image, showing a cut-out section of a superconducting dipole magnet. The beam pipes are represented as clear tubes, with counter-rotating proton beams shown in red and blue</span> <span class="attribution"><a class="source" href="http://home.web.cern.ch/about/updates/2015/02/cerns-two-year-shutdown-drawing-close">Daniel Dominguez/CERN</a></span></figcaption></figure><p>Since <a href="https://theconversation.com/goodbye-for-a-while-to-the-large-hadron-collider-12238">shutting down</a> in early 2013, the most powerful particle accelerator on the planet, the <a href="http://home.web.cern.ch/topics/large-hadron-collider">Large Hadron Collider</a> (LHC), has been sitting dormant. Over the past two years this scientific colossus situated at CERN near Geneva, Switzerland, has undergone a series of repairs and upgrades. But now it is ready to reawaken from it’s slumber. </p>
<p>This new era will see a collider with almost double the previous energy, with collisions at <a href="http://home.web.cern.ch/about/engineering/restarting-lhc-why-13-tev">13 TeV</a>. Scaled up into our macroscopic world, the force of these collisions between protons is roughly equivalent to an apple hitting the moon hard enough to create a crater more than 9.5km (6 miles) across. </p>
<p>This new energy frontier will allow researchers to probe beyond the current boundaries of our understanding of the fundamental structure of matter in search of new discoveries.</p>
<h2>Detector upgrades</h2>
<p>In order to make the most of the new accelerator conditions, the discovery experiments, ATLAS and CMS, have undergone further upgrades during the shutdown period. </p>
<p>Most notably the <a href="http://home.web.cern.ch/about/experiments/atlas">ATLAS experiment</a> has added an entirely new detector, the <a href="http://atlas.ch/news/2014/a-new-sub-detector-for-ATLAS.html">Insertable b-Layer</a>, or IBL. This sits very close to the point where the protons slam into each other, creating a cascade of other subatomic particles.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72735/original/image-20150223-21879-vohz2t.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A visualisation of particles colliding in the ATLAS detector back in 2012. New experiments will be run at a higher energy and may yield even more startling results.</span>
<span class="attribution"><a class="source" href="http://cds.cern.ch/record/1459496">ATLAS team/CERN</a></span>
</figcaption>
</figure>
<p>Because the IBL sits closer to the action than the original detectors – which are also still in use – it provides an additional measurement point for particles originating from the collisions, allowing greater accuracy on the resulting measurements. </p>
<p>The IBL will be especially important for identifying heavy particles, such as <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html">bottom quarks</a>, which are produced during decays of short-lived particles such as the Higgs boson and are crucial for measurements of the top quark (which decays to a bottom quark and <a href="http://home.web.cern.ch/about/physics/w-boson-sunshine-and-stardust">W boson</a>). </p>
<h2>Beyond the Higgs boson</h2>
<p>During the first run of the LHC in 2012, the ATLAS and <a href="http://home.web.cern.ch/about/experiments/cms">CMS</a> experiments ended the 50 year hunt for the <a href="https://theconversation.com/explainer-the-higgs-boson-particle-280">Higgs boson</a>, which was predicted by the <a href="http://physics.info/standard/">Standard Model</a> –- a theory governing all particles, forces and interactions. </p>
<p>Having measured the mass of the Higgs boson by looking at the way it decays into other particles, LHC scientists then went one step further. In 2013 they measured the properties of the boson, all of which proved consistent with the predictions of the Standard Model. </p>
<p>Now physicists want to know if the Higgs they found is hiding any surprises. And, perhaps more importantly, what may be lurking beyond it. The increase in LHC energy is coupled with an increase in <a href="http://www.lhc-closer.es/1/4/9/0">luminosity</a>, which allows physicists to probe rare events with greater frequency. </p>
<p>This high luminosity in concert with the increase in energy provides an unprecedented environment to interrogate fundamental physics beyond the limits of our current knowledge. The first thing to do with the new data is to study the Higgs boson in depth to see if anything disagrees with prediction. </p>
<p>This could be a window into new physics. Because the Higgs boson loves mass, scientists suspect that it might interact with a range of hidden, massive particles that we cannot see, such as potential candidates for <a href="https://theconversation.com/au/topics/dark-matter">dark matter</a>. </p>
<p>If the Higgs boson is partying with as yet undiscovered particles, physicists hope that their newly improved particle collider and upgraded detector instruments will allow them to crash the party -– and find out something about the attendees!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=781&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=781&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=781&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=981&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=981&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72739/original/image-20150223-19701-10s5fbw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=981&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Candidate Higgs boson events from collisions between protons in the LHC. The top event in the CMS experiment shows a decay into two photons (dashed yellow lines and green towers). The lower event in the ATLAS experiment shows a decay into four muons (red tracks).</span>
<span class="attribution"><a class="source" href="http://cds.cern.ch/record/1630222">ATLAS and CMS, Collaborations</a></span>
</figcaption>
</figure>
<h2>Supersymmetry, dark matter and other exotica</h2>
<p>Even if the Higgs boson were to continue to agree with the Standard Model predictions, the value of its mass is still suggestive of other interesting goings-on in the universe. </p>
<p>When LHC physicists measured the Higgs mass, they found it was lower than what they anticipated. This might make sense if it was being caused – or protected – by one or more particles that exist at a higher mass and were governed by some new “symmetry”. </p>
<p><a href="https://theconversation.com/could-the-higgs-nobel-be-the-end-of-particle-physics-18978">Supersymmetry</a> is one such extension of the Standard Model that would yield additional partners of the known objects that may appear in high-energy LHC collisions. </p>
<p>These particles could act as “bodyguards” of the Higgs, influencing its measured mass. These supersymmetric particles could potentially be produced in the next run of the LHC, perhaps even as early as this year. </p>
<p>One natural consequence of certain supersymmetric models is the production of invisible stable massive particles that are weakly interacting. Such a particle would be an excellent candidate for dark matter, the mysterious invisible matter that we have thus far only detected via its gravitational effect. </p>
<p>Providing clues as to the nature of dark matter is one of the main motivators of the increased energy and intensity of the LHC collisions. Any evidence of dark matter and/or results consistent with supersymmetry would be hugely significant and would open up a new chapter in our understanding of the universe at a fundamental level. </p>
<p>But the experiments must be prepared for <em>any</em> possible signature to be manifested in their collisions, and subsequently mine the data for evidence of exotic resonant structures, extra dimensions or long-lived particles among many other possibilities.</p>
<p>So 2015 promises to be a once in a lifetime opportunity for a generation of physicists who will turn on and commission a machine at unprecedented energies. With new discoveries potentially just around the corner this may well be a defining time in the field of high energy particle physics.</p><img src="https://counter.theconversation.com/content/37638/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Paul Jackson works in the Department of Physics at the University of Adelaide. He receives funding from the Australian Research Council under the Future Fellowship scheme. He is affiliated with the ARC Centre of Excellence for Particle Physics and the Terascale and is the recipient of a 2015 Australia-Harvard Fellowship.</span></em></p>The Large Hadron Collider is ramping up to probe even deeper into the fundamental constituents of matter.Paul Jackson, Particle physicist, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/267842014-06-13T04:54:50Z2014-06-13T04:54:50ZScience stories: Particle Fever tries too hard to tell us a tale<figure><img src="https://images.theconversation.com/files/50844/original/fdf2d923-1402492945.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The five storey Swiss watch.</span> </figcaption></figure><p>The challenge for the documentary filmmaker is to persuade the viewer to take the images and sounds with which they are presented for the world itself. The documentary viewer willingly collaborates in this project because we want to see what’s real. So for the filmmaker, the challenge really becomes how not to make a mess of things, how not to make it difficult for the viewer to believe that what they see and hear really is the case. </p>
<p>This is where organising the documentary text as a story becomes problematic, for at some level we all sense that stories are artificial. Of course stories are also wonderful because they make sense of things; they hold our interest as life does not. Consequently a great many documentaries are structured as stories. Science documentaries, forever seeking popular appeal, almost always are. </p>
<p><a href="http://particlefever.com/">Particle Fever</a> is a feature length science documentary, showing at various film festivals this summer. It is a fine example of this tendency. The film tells the gripping story of the enormous collaborative effort to find and take the measure of the Higgs, the elusive sub-atomic particle considered by scientists the “lynch-pin” of the so-called “Standard Model”, the name given by physicists to their current understanding of the nature of matter and the universe. The film focuses mainly on the feverish final weeks of the 30 year project, and climaxes with the return of the experiment’s first results on July 4th 2012. </p>
<p>A lot hinges, we are told, on the success of this multi-billion dollar experiment. If the Higgs is not found, then Science’s understanding of things must be deeply wrong. But with the particle in hand, scientists will be able to decide a profound dispute: whether the universe is a beautifully ordered place ruled by universal laws, or a chaotic place where the values of things such as the speed of light are essentially random, a place where doing physics is therefore pretty pointless. </p>
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<p>Although their <em>dramatis personae</em> may vary, stories have a highly conventional form and Particle Fever is no exception. In this film, a series of heroes are dispatched from the village of Science to bring home what is lacking (the Higgs). Each incarnation of the hero is aided in their quest by the magical “five storey Swiss watch” that is the Large Hadron Collider at CERN. Sometimes the heroes are frustrated by villains (mostly in the form of gremlins in the machinery) but ultimately they overcome these and other challenges and return home with the coveted prize to receive their reward. </p>
<p>This triumphant return is set to Beethoven’s <a href="http://www.youtube.com/watch?v=Wod-MudLNPA&feature=kp">Ode to Joy</a>. No doubt the assembled thousands at CERN, many of whom had dedicated years to the project, felt joyful at the proper functioning of their remarkable machine. You’d have to have a heart of stone not to share their emotion. But once the moment has passed a different feeling sets in, a feeling, dare I say it, of emptiness. The narrative has run its course and for the layperson at least we are left wondering what it all adds up to. What have we really seen? </p>
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<span class="caption">Jubilation.</span>
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<p>There is a telling moment early on in the film that suggests an explanation for this feeling. The physicist David Kaplan is describing the project at a conference. When he finishes he invites questions from his audience. A self-avowed economist pipes up asking him to justify the cost – what benefits will it bring? Kaplan sweeps the question aside with a spurious comparison to Hertz’s discovery of radio waves, which, like the Higgs, had no obvious application at the time. </p>
<p>Of course Kaplan has a perfect right to sidestep the economist’s challenge, but this is the only part of the Q & A the editor, Apocalypse Now’s Walter Murch, chose to leave in the film. And he did so not so much because of its “content” as because of its “action”. What we see is the hero besting the villainous philistine, a moment that fits neatly into the film’s narrative structure. We don’t see any engagement with the economic (or any other) questions the project naturally raises. The needs of Story leave no room for that.</p>
<p>The filmmakers clearly recognise that this is a problem because they try – too late – to fix it. Once the story of the experiment is over we are given a sort of philosophical postscript, a reflection on the meaning of it all. The very last thing we see and hear is an interview with the physicist Savas Dimopoulos, who reflects on this seeming paradox: “the things that are least important for our survival are the very things that make us human.” In the end, the film seems to be saying that it doesn’t matter if you can’t grasp the significance of particle physics because what this documentary has really been about is something else: science as a human endeavour, science as culture. </p>
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<p>But if that’s what the film seeks to explore then it falls short. In shaping their material primarily as a story about the heroic conquest of nature, the filmmakers leave little room to show anything more interesting about the nature of science and scientific endeavour. The heroes of Particle Fever are necessarily stereotypes and the picture of their work is an idealised, apolitical vision of selfless brainboxes labouring together in pursuit of knowledge for knowledge’s sake. And don’t get me wrong, it makes for a fantastic story. But although this romantic image may thrill us at the time, when the story’s tension ebbs away it leaves us feeling empty because we’ve seen little that is convincingly particular, convincingly real about the complex cultural phenomenon that is professional science. </p>
<p>There are some moments that hint at what becomes possible when the iron discipline of narrative is relaxed. In one of them, two physicists are playing ping pong when one spontaneously improvises a new, more challenging version of the game in which the players use the walls as well as the table-top. It’s a delightful scene expressing at one and the same time the creativity of these scientists and their competitive natures. </p>
<p>Clearly such moments do not a documentary make but in their spontaneity we sense the real world that narrative cannot comfortably contain. The documentary, if it is to persuasively represent the fabric of reality, must balance our appetite for Story with our desire for the particular and our nose for the contrived. </p><img src="https://counter.theconversation.com/content/26784/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Sternberg does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The challenge for the documentary filmmaker is to persuade the viewer to take the images and sounds with which they are presented for the world itself. The documentary viewer willingly collaborates in…Robert Sternberg, Lecturer in Humanities, Imperial College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/254652014-04-09T16:41:10Z2014-04-09T16:41:10ZQuirky quark combination creates exotic new particle<figure><img src="https://images.theconversation.com/files/46018/original/m2pxsmg4-1397058718.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">And then it falls apart, a bit like this.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/brookhavenlab/3148787798">brookhavenlab</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>Since the spectacular discovery of the Higgs boson in 2012, physicists at the Large Hadron Collider (LHC), the gigantic particle accelerator outside Geneva, have suffered <a href="https://theconversation.com/could-the-higgs-nobel-be-the-end-of-particle-physics-18978">a bit of a drought</a> when it comes to finding new particles. In a welcome relief, the <a href="http://lhcb-public.web.cern.ch/lhcb-public/">LHCb collaboration</a>, who run one of four large experiments at the LHC, have announced one of the most genuinely exciting observations to come out of the 27km super-collider so far – an exotic particle that cannot be explained by current theories.</p>
<p>In the early 1930s physicists had a clean picture of the subatomic particles that make up our world. Every known atom has a tiny nucleus at its heart surrounded by a cloud of electrons, and each nucleus was made out of varying numbers of protons and neutrons. However, as the decades wore on a number of new, and somewhat unwelcome, particles were discovered, at first in detectors studying particles from outer space and later in particle-collider experiments.</p>
<p>By the 1950s, dozens of apparently elementary particles had been discovered, causing frustration among physicists who often brandish an inability to memorise a list of facts as a badge of honour. The famous physicist Enrico Fermi perhaps best expressed the mood of his colleagues in an infamous remark: </p>
<blockquote>
<p>“Young man, if I could remember the names of these particles, I would have been a botanist.”</p>
</blockquote>
<p>Help came in the 1950s when physicists came up with a new model that explained most of these particles as being made up of a small number of truly elementary particles. Borrowing a line from James Joyce’s Finnegans Wake (a book that is even harder to understand than quantum field theory), Murray Gell-Mann dubbed these new particles “quarks”. </p>
<p>By the late 1960s the existence of quarks had been verified experimentally. We now know that there are six in total – the up, down, strange, charm, bottom and top quarks, along with six antiquarks (their anti-matter copies).</p>
<p>The quark model neatly explained all these peculiar particles. Protons, neutrons and many others besides are made of three quarks, belonging to a family known as baryons. Alternatively, a quark and an antiquark can pair up to form a meson. </p>
<p>Since then the quark model has been extremely successful, and is now a cornerstone of our understanding of particle physics. It was only at the turn of the millennium that some strange results started to suggest that the model might be incomplete. Until 2003 quarks had only been seen in twos or threes, but then a number of particles that looked like combinations of four quarks started to reveal themselves. </p>
<p>In 2008 the Belle Collaboration in Japan reported the observation of a new exotic particle – the unfortunately drably named Z(4430)<sup>–</sup> (where <sup>–</sup> for its negative charge). This has a mass that places it in a dense forest of charmonium states – particles that are made up of a charm quark and a charm antiquark. Crucially though, the Z is electrically charged whereas all charmonium states must be neutral, clearly marking it out as something unusual.</p>
<p>After a careful analysis of data from 25,000 decays of mesons resulting from more than 180 trillion collisions at the LHC in 2011 and 2012, the new announcement confirms the existence of Z(4430)<sup>–</sup> with extremely high confidence. The particle was observed with an overwhelming significance of 13.9 sigma, well above the usual 5 sigma threshold required to declare a discovery. LHCb also went further than Belle by measuring the spin and parity of Z(4430)<sup>–</sup>, two quantum-mechanical properties that give a firm handle on the internal makeup of the particle.</p>
<p>The observation by LHCb is important because few physicists will take a result seriously until it has been seen by two independent experiments. This is why hundreds of millions of Euros were spent building two large detectors at the LHC. The observation of the Higgs boson by two independent teams, ATLAS and CMS, was what really convinced the scientific community that the particle was real.</p>
<p>This result is the clearest evidence yet of the existence of a tetraquark – a four-quark state, with the LHCb analysis suggesting that Z(4430)<sup>–</sup> is most likely to be made of a charm, anti-charm, down and anti-up quark. Theorists are now able to add a whole new type of particle to the quark model and begin the hard work of trying to understand exactly how these four quarks are bound together.</p>
<p>Meanwhile, physicists working at the LHC experiments will continue to explore unmapped regions of the subatomic world, with the hope of turning up more members of this exotic new family. Now that we know that at least one is out there, it is very unlikely that Z(4430)<sup>–</sup> is alone.</p><img src="https://counter.theconversation.com/content/25465/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Harry Cliff is affiliated with the University of Cambridge, CERN, the LHCb experiment.</span></em></p>Since the spectacular discovery of the Higgs boson in 2012, physicists at the Large Hadron Collider (LHC), the gigantic particle accelerator outside Geneva, have suffered a bit of a drought when it comes…Harry Cliff, Particle Physicist and Science Museum Fellow, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/208822013-12-01T19:28:06Z2013-12-01T19:28:06ZHiggs boson’s decay confirms physics model works<figure><img src="https://images.theconversation.com/files/36483/original/qwbhsjb4-1385687354.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">We knew the HIggs boson decayed into bosons; now we've seen it crumble into fermions.</span> <span class="attribution"><span class="source">ATLAS</span></span></figcaption></figure><p>Last week, the <a href="http://atlas.ch/">ATLAS</a> experiment at the <a href="https://theconversation.com/topics/large-hadron-collider">Large Hadron Collider</a> in Switzerland, showed evidence for the first time that a <a href="https://theconversation.com/topics/higgs-boson">Higgs boson</a> decays into a <a href="http://atlas.ch/news/2013/higgs-into-fermions.html">pair of tau particles</a>. It is one of the crucial results that has followed on from the discovery of the Higgs boson. </p>
<p>But what makes this result so important?</p>
<p>On July 4, 2012, two experiments (ATLAS and CMS) at CERN announced the discovery of <a href="https://theconversation.com/cern-discovers-a-higgs-like-particle-let-the-party-and-head-scratching-begin-8036">a new boson particle</a>. </p>
<p>Later in the same year, the new particle was <a href="https://theconversation.com/definitely-maybe-evidence-grows-for-positive-id-of-higgs-boson-12790">confirmed</a> as the Higgs boson. Ever since, scientists have been working to pin down the properties of the particle.</p>
<p>The Higgs particle is a very unstable. Once it’s produced, it disintegrates (or decays) immediately into other light stable particles. Scientists hoped to find both the rate of its disintegration, and the particles it disintegrates into.</p>
<h2>Breaking it down</h2>
<p>All of nature is <a href="http://nonlocal.com/hbar/bosonfermion.html">made up of bosons and fermions</a>. The difference between the two types of particles is the way they spin, and that bosons are “gregarious” while fermions are “solitary”. Bosons include, among other things, photons, gluons, W and Z particles. Fermions include leptons and quarks.</p>
<p>At the time of discovery, the Higgs boson was seen to disintegrate into a pair of bosons; that is, into a <a href="http://www.universetoday.com/74027/what-are-photons/">pair of photons</a> and a pair of W or Z particles.</p>
<p>The <a href="https://theconversation.com/explainer-standard-model-of-particle-physics-2539">Standard Model of Particle Physics</a> predicts that Higgs can decay into fermions in addition to bosons. But the decay rates can be different. </p>
<p>The scientists’ job is to confirm or to rule out the possibility of the Higgs boson’s decay into fermions. Any deviation from the prediction would give rise to something new, something never observed before.</p>
<p>Scientists were investigating specifically whether the Higgs decayed into [tau particles](http://en.wikipedia.org/wiki/Tau_(particle); these are a type of fermion and the heavy cousin of electrons. A tau’s mass is a few thousand times higher than that of an electron. </p>
<p>The preliminary results of the ATLAS collaboration at CERN show clear evidence of such decay. The decay rates are consistent with the Standard Model predictions.</p>
<h2>Future hits</h2>
<p>The first run of the Large Hadron Collider finished earlier this year and the second run will start in 2015. The collider will operate at higher energies and produce several time more collisions and hence more Higgs bosons. The additional data from these runs will shed more light on these initial findings. </p>
<p>It will be important to study other possible fermionic decays when the collider is restarted. For example, scientists will be looking at whether Higgs decays into a pair of muons, another type of fermion lighter than tau but heavier than an electron.</p>
<p>In addition to important Higgs studies, the ATLAS experiment is searching for new or rare phenomena in nature. These include <a href="http://hitoshi.berkeley.edu/public_html/susy/susy.html">super-symmetric partners</a>, evidence of a <a href="http://cdms.berkeley.edu/Education/DMpages/essays/candidates.shtml">dark matter candidate</a> and the existence of <a href="http://ctp.berkeley.edu/extraD.html">extra-dimensions of space</a>.</p><img src="https://counter.theconversation.com/content/20882/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nitesh Soni does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Last week, the ATLAS experiment at the Large Hadron Collider in Switzerland, showed evidence for the first time that a Higgs boson decays into a pair of tau particles. It is one of the crucial results…Nitesh Soni, ARC Research Associate (Centre of Excellence for Particle Physics at Tera Scale), University of AdelaideLicensed as Creative Commons – attribution, no derivatives.