Latest news with #FermiNationalAcceleratorLaboratory
Toronto Star
10-06-2025
- Science
- Toronto Star
Fermilab: Muon g-2 announces most precise measurement of the magnetic anomaly of the muon
Batavia, Ill., June 04, 2025 (GLOBE NEWSWIRE) — Scientists working on the Muon g-2 experiment, hosted by the U.S. Department of Energy's Fermi National Accelerator Laboratory, have released their third and final measurement of the muon magnetic anomaly. This value is related to g-2, the experiment's namesake measurement. The final result agrees with their published results from 2021 and 2023 but with a much better precision of 127 parts-per-billion, surpassing the original experimental design goal of 140 parts-per-billion. 'The anomalous magnetic moment, or g–2, of the muon is important because it provides a sensitive test of the Standard Model of particle physics. This is an exciting result and it is great to see an experiment come to a definitive end with a precision measurement,' said Regina Rameika, the U.S. Department of Energy's Associate Director for the Office of High Energy Physics.
Yahoo
10-06-2025
- Science
- Yahoo
A Blockbuster ‘Muon Anomaly' May Have Just Disappeared
The Standard Model of particle physics—the best, most thoroughly vetted description of reality scientists have ever devised—appears to have fended off yet another threat to its reign. At least, that's one interpretation of a long-awaited experimental result announced on June 3 by physicists at the Fermi National Accelerator Laboratory, or Fermilab, in Batavia, Ill. An alternative take would be that the result—the most precise measurement ever made of the magnetic wobble of a strange subatomic particle called the muon—still remains the most significant challenge to the Standard Model's supremacy. The results have been posted on the preprint server and submitted to the journal Physical Review Letters. The muon is the electron's less stable, 200-times-heavier cousin. And like the electron and all other charged particles, it possesses an internal magnetism. When the muon's inherent magnetism clashes with an external magnetic field, the particle precesses, torquing to and fro like a wobbling, spinning top. Physicists describe the speed of this precession using a number, g, which almost a century ago was theoretically calculated to be exactly 2. Reality, however, prefers a slightly different value, arising from the wobbling muon being jostled by a surrounding sea of 'virtual' particles flitting in and out existence in the quantum vacuum. The Standard Model can be used to calculate the size of this deviation, known as g−2, by accounting for all the influences of the various known particles. But because g−2 should be sensitive to undiscovered particles and forces as well, a mismatch between a calculated deviation and an actual measurement could be a sign of new physics beyond the vaunted Standard Model's limits. [Sign up for Today in Science, a free daily newsletter] That's the hope, anyway. The trouble is that physicists have found two different ways to calculate g−2, and one of those methods, per a separate preprint paper released on May 27, now gives an answer that closely matches the measurement of the muon anomalous magnetic moment, the final result from the Muon g−2 Experiment hosted at Fermilab. So a cloud of uncertainty still hangs overhead: Has the most significant experimental deviation in particle physics been killed off by theoretical tweaks just when its best-yet measurement has arrived, or is the muon g−2 anomaly still alive and well? Vexingly, the case can't yet be conclusively closed. The Muon g−2 Collaboration announced the results on Tuesday in a packed auditorium at Fermilab, offering the audience (which included more than 1,000 people watching via livestream) a brief history of the project and an overview of its final outcome. The heart of the experiment is a giant 50-foot-diameter magnet, which acts as a racetrack for wobbling muons. In 2001, while operating at Brookhaven National Laboratory on Long Island, this ring revealed the initial sign of a tantalizing deviation. In 2013 physicists painstakingly moved the ring by truck and barge from Brookhaven to Fermilab, where it could take advantage of a more powerful muon source. The Muon g−2 Collaboration began in 2017. And in 2021 it released the first result that strengthened earlier hints of an apparent anomaly, which was bolstered further by additional results announced in 2023. This latest result is a capstone to those earlier measurements: the collaboration's final measurement gives a value of 0.001165920705 for g−2, consistent with previous results but with a remarkable precision of 127 parts per billion. That's roughly equivalent, it was noted during the June 3 announcement, to measuring the weight of a bison to the precision of a single sunflower seed. Despite that impressive feat of measurement, interpretation of this result remains an entirely different matter. The task of calculating Standard Model predictions for g−2 is so gargantuan that it brought together more than 100 theorists for a supplemental project called the Muon g−2 Theory Initiative. 'It is a community effort with the task to come up with a consensus value based on the entire available information at the time,' says Hartmut Wittig, a professor at the University of Mainz in Germany and a member of the theory initiative's steering committee. 'The answer to whether there is new physics may depend on which theory prediction you compare against. The consensus value should put an end to this ambiguity.' In 2020 the group published a theoretical calculation of g−2 that appeared to confirm the discrepancy with the measurements. The May preprint, however, brought significant change. The difference between theory and experiment is now less than one part per billion, a number both minuscule and much smaller than the accompanying uncertainties, which has led to the collaboration's consensus declaration that there is 'no tension' between the Standard Model's predictions and the measured result. To understand what brought this shift in the predictions, one has to look at one category of the virtual particles that cross the muons' path. '[Excepting gravity] three out of the four known fundamental forces contribute to g−2: electromagnetism, the weak interaction and the strong interaction,' Wittig explains. The influence of virtual photons (particles of light that are also carriers of the electromagnetic force) on muons is relatively straightforward (albeit still laborious) to calculate, for instance. In contrast, precisely determining the effects of the strong force (which usually holds the nuclei of atoms together) is much harder and is the least theoretically constrained among all g−2 calculations. Instead of dealing with virtual photons, those calculations grapple with virtual hadrons, which are clumps of fundamental particles called quarks glued together by other particles called (you might have guessed) gluons. Hadrons can interact with themselves to create tangled, precision-scuttling messes that physicists refer to as 'hadronic blobs,' enormously complicating calculations of their contributions to the wobbling of muons. Up to the 2020 result, researchers indirectly estimated this so-called hadronic vacuum polarization (HVP) contribution to the muon g−2 anomaly by experimentally measuring it for electrons. One year later, though, a new way of calculating HVP was introduced based on lattice quantum chromodynamics (lattice QCD), a computationally intensive methodology, and quickly caught on. Gilberto Colangelo, a professor at the University of Bern in Switzerland and a member of the theory initiative's steering committee, points out that, currently, 'on the lattice QCD side, there is a coherent picture emerging from different approaches. The fact that they agree on the result is a very good indication that they are doing the right thing.' While the multiple flavors of lattice QCD computations improved and their results converged, though, the experimental electron-based measurements of HVP went the opposite way. Among seven experiments seeking to constrain HVP and tighten predictive precision, only one agreed with the lattice QCD results, while there was also deviation among their own measurements. 'This is a puzzling situation for everyone,' Colangelo notes. 'People have made checks against each other. The [experiments] have been scrutinized in detail; we had sessions which lasted five hours.... Nothing wrong was found.' Eventually, the theory initiative decided to use only the lattice QCD results for the HVP factor in this year's white paper, while work on understanding the experimental results is going on. The choice moved the total predicted value for g−2 much closer to Fermilab's measurement. The Standard Model has seen all of its predictions experimentally tested to high precision, giving it the title of the most successful theory in history. Despite this, it is sometimes described as something unwanted or even failed because it does not address general open questions, such as the nature of dark matter hiding in galaxies. In the solid terms of experimental deviations from its predictions, this century has seen the rise and fall of many false alarms. If the muon g−2 anomaly goes away, however, it will also take down some associated contenders for new, paradigm-shifting physics; the absence of novel types of particles in the quantum vacuum will put strong constraints on 'beyond the Standard Model' theories. This is particularly true for the theory of supersymmetry, a favorite among theorists, some of whom have tailored a plethora of predictions explaining away the muon g−2 anomaly as a product of as-yet-unseen supersymmetric particles. Kim Siang Khaw, an associate professor at Shanghai Jiao Tong University in China and a member of Fermilab's Muon g−2, offers a perspective on what will follow. 'The theory initiative is still a work in progress,' he says. 'They may have to wait several more years to finalize. [But] every physics study is a work in progress.' Khaw also mentions that currently Fermilab is looking into repurposing the muon 'storage ring' and magnet used in the experiment, exploring more ideas that can be studied with it. Finally, on the theory front, he muses: 'I think the beauty of [the g−2 measurement] and the comparison with the theoretical calculation is that no matter if there is an anomaly or no anomaly, we learn something new about nature. Of course, the best scenario would be that we have an anomaly, and then we know where to look for this new physics. [But] if there is nothing here, then we can look somewhere else for a higher chance of discovering new physics.'
Scientific American
09-06-2025
- Science
- Scientific American
Do Wobbling Muons Point the Way to New Physics?
The Standard Model of particle physics—the best, most thoroughly vetted description of reality scientists have ever devised—appears to have fended off yet another threat to its reign. At least, that's one interpretation of a long-awaited experimental result announced on June 3 by physicists at the Fermi National Accelerator Laboratory, or Fermilab, in Batavia, Ill. An alternative take would be that the result—the most precise measurement ever made of the magnetic wobble of a strange subatomic particle called the muon —still remains the most significant challenge to the Standard Model's supremacy. The results have been posted on the preprint server and submitted to the journal Physical Review Letters. The muon is the electron's less stable, 200-times-heavier cousin. And like the electron and all other charged particles, it possesses an internal magnetism. When the muon's inherent magnetism clashes with an external magnetic field, the particle precesses, torquing to and fro like a wobbling, spinning top. Physicists describe the speed of this precession using a number, g, which almost a century ago was theoretically calculated to be exactly 2. Reality, however, prefers a slightly different value, arising from the wobbling muon being jostled by a surrounding sea of 'virtual' particles flitting in and out existence in the quantum vacuum. The Standard Model can be used to calculate the size of this deviation, known as g−2, by accounting for all the influences of the various known particles. But because g−2 should be sensitive to undiscovered particles and forces as well, a mismatch between a calculated deviation and an actual measurement could be a sign of new physics beyond the vaunted Standard Model's limits. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. That's the hope, anyway. The trouble is that physicists have found two different ways to calculate g−2, and one of those methods, per a separate preprint paper released on May 27, now gives an answer that closely matches the measurement of the muon anomalous magnetic moment, the final result from the Muon g−2 Experiment hosted at Fermilab. So a cloud of uncertainty still hangs overhead: Has the most significant experimental deviation in particle physics been killed off by theoretical tweaks just when its best-yet measurement has arrived, or is the muon g−2 anomaly still alive and well? Vexingly, the case can't yet be conclusively closed. The Latest Word—But Not the Last The Muon g−2 Collaboration announced the results on Tuesday in a packed auditorium at Fermilab, offering the audience (which included more than 1,000 people watching via livestream) a brief history of the project and an overview of its final outcome. The heart of the experiment is a giant 50-foot-diameter magnet, which acts as a racetrack for wobbling muons. In 2001, while operating at Brookhaven National Laboratory on Long Island, this ring revealed the initial sign of a tantalizing deviation. In 2013 physicists painstakingly moved the ring by truck and barge from Brookhaven to Fermilab, where it could take advantage of a more powerful muon source. The Muon g−2 Collaboration began in 2017. And in 2021 it released the first result that strengthened earlier hints of an apparent anomaly, which was bolstered further by additional results announced in 2023. This latest result is a capstone to those earlier measurements: the collaboration's final measurement gives a value of 0.001165920705 for g−2, consistent with previous results but with a remarkable precision of 127 parts per billion. That's roughly equivalent, it was noted during the June 3 announcement, to measuring the weight of a bison to the precision of a single sunflower seed. Despite that impressive feat of measurement, interpretation of this result remains an entirely different matter. The task of calculating Standard Model predictions for g−2 is so gargantuan that it brought together more than 100 theorists for a supplemental project called the Muon g−2 Theory Initiative. 'It is a community effort with the task to come up with a consensus value based on the entire available information at the time,' says Hartmut Wittig, a professor at the University of Mainz in Germany and a member of the theory initiative's steering committee. 'The answer to whether there is new physics may depend on which theory prediction you compare against. The consensus value should put an end to this ambiguity.' In 2020 the group published a theoretical calculation of g−2 that appeared to confirm the discrepancy with the measurements. The May preprint, however, brought significant change. The difference between theory and experiment is now less than one part per billion, a number both minuscule and much smaller than the accompanying uncertainties, which has led to the collaboration's consensus declaration that there is 'no tension' between the Standard Model's predictions and the measured result. Virtual (Particle) Insanity To understand what brought this shift in the predictions, one has to look at one category of the virtual particles that cross the muons' path. '[Excepting gravity] three out of the four known fundamental forces contribute to g−2: electromagnetism, the weak interaction and the strong interaction,' Wittig explains. The influence of virtual photons (particles of light that are also carriers of the electromagnetic force) on muons is relatively straightforward (albeit still laborious) to calculate, for instance. In contrast, precisely determining the effects of the strong force (which usually holds the nuclei of atoms together) is much harder and is the least theoretically constrained among all g−2 calculations. Instead of dealing with virtual photons, those calculations grapple with virtual hadrons, which are clumps of fundamental particles called quarks glued together by other particles called (you might have guessed) gluons. Hadrons can interact with themselves to create tangled, precision-scuttling messes that physicists refer to as 'hadronic blobs,' enormously complicating calculations of their contributions to the wobbling of muons. Up to the 2020 result, researchers indirectly estimated this so-called hadronic vacuum polarization (HVP) contribution to the muon g−2 anomaly by experimentally measuring it for electrons. One year later, though, a new way of calculating HVP was introduced based on lattice quantum chromodynamics (lattice QCD), a computationally intensive methodology, and quickly caught on. Gilberto Colangelo, a professor at the University of Bern in Switzerland and a member of the theory initiative's steering committee, points out that, currently, 'on the lattice QCD side, there is a coherent picture emerging from different approaches. The fact that they agree on the result is a very good indication that they are doing the right thing.' While the multiple flavors of lattice QCD computations improved and their results converged, though, the experimental electron-based measurements of HVP went the opposite way. Among seven experiments seeking to constrain HVP and tighten predictive precision, only one agreed with the lattice QCD results, while there was also deviation among their own measurements. 'This is a puzzling situation for everyone,' Colangelo notes. 'People have made checks against each other. The [experiments] have been scrutinized in detail; we had sessions which lasted five hours.... Nothing wrong was found.' Eventually, the theory initiative decided to use only the lattice QCD results for the HVP factor in this year's white paper, while work on understanding the experimental results is going on. The choice moved the total predicted value for g−2 much closer to Fermilab's measurement. The Standard Model Still Stands Tall The Standard Model has seen all of its predictions experimentally tested to high precision, giving it the title of the most successful theory in history. Despite this, it is sometimes described as something unwanted or even failed because it does not address general open questions, such as the nature of dark matter hiding in galaxies. In the solid terms of experimental deviations from its predictions, this century has seen the rise and fall of many false alarms. If the muon g−2 anomaly goes away, however, it will also take down some associated contenders for new, paradigm-shifting physics; the absence of novel types of particles in the quantum vacuum will put strong constraints on 'beyond the Standard Model' theories. This is particularly true for the theory of supersymmetry, a favorite among theorists, some of whom have tailored a plethora of predictions explaining away the muon g−2 anomaly as a product of as-yet-unseen supersymmetric particles. Kim Siang Khaw, an associate professor at Shanghai Jiao Tong University in China and a member of Fermilab's Muon g−2, offers a perspective on what will follow. 'The theory initiative is still a work in progress,' he says. 'They may have to wait several more years to finalize. [But] every physics study is a work in progress.' Khaw also mentions that currently Fermilab is looking into repurposing the muon 'storage ring' and magnet used in the experiment, exploring more ideas that can be studied with it. Finally, on the theory front, he muses: 'I think the beauty of [the g−2 measurement] and the comparison with the theoretical calculation is that no matter if there is an anomaly or no anomaly, we learn something new about nature. Of course, the best scenario would be that we have an anomaly, and then we know where to look for this new physics. [But] if there is nothing here, then we can look somewhere else for a higher chance of discovering new physics.'
The Hindu
04-06-2025
- General
- The Hindu
A long-running experiment finds a tiny particle is still acting weird
Final results from a long-running U.S.-based experiment announced Tuesday show a tiny particle continues to act strangely — but that's still good news for the laws of physics as we know them. 'This experiment is a huge feat in precision,' said Tova Holmes, an experimental physicist at the University of Tennessee, Knoxville who is not part of the collaboration. The mysterious particles called muons are considered heavier cousins to electrons. They wobble like a top when inside a magnetic field, and scientists are studying that motion to see if it lines up with the foundational rulebook of physics called the Standard Model. Experiments in the 1960s and 1970s seemed to indicate all was well. But tests at Brookhaven National Laboratory in the late 1990s and early 2000s produced something unexpected: the muons weren't behaving like they should. Decades later, an international collaboration of scientists decided to rerun the experiments with an even higher degree of precision. The team raced muons around a magnetic, ring-shaped track — the same one used in Brookhaven's experiment — and studied their signature wiggle at the Fermi National Accelerator Laboratory near Chicago. The first two sets of results — unveiled in 2021 and 2023 — seemed to confirm the muons' weird behavior, prompting theoretical physicists to try to reconcile the new measurements with the Standard Model. Now, the group has completed the experiment and released a measurement of the muon's wobble that agrees with what they found before, using more than double the amount of data compared to 2023. They submitted their results to the journal Physical Review Letters. That said, it's not yet closing time for our most basic understanding of what's holding the universe together. While the muons raced around their track, other scientists found a way to more closely reconcile their behavior with the Standard Model with the help of supercomputers. There's still more work to be done as researchers continue to put their heads together and future experiments take a stab at measuring the muon wobble — including one at the Japan Proton Accelerator Research Complex that's expected to start near the end of the decade. Scientists also are still analyzing the final muon data to see if they can glean information about other mysterious entities like dark matter. 'This measurement will remain a benchmark ... for many years to come,' said Marco Incagli with the National Institute for Nuclear Physics in Italy. By wrangling muons, scientists are striving to answer fundamental questions that have long puzzled humanity, said Peter Winter with Argonne National Laboratory. 'Aren't we all curious to understand how the universe works?' said Winter.
Toronto Sun
03-06-2025
- General
- Toronto Sun
Long-running experiment finds tiny particle is still acting weird: 'Huge feat in precision'
The mysterious particles called muons are considered heavier cousins to electrons Published Jun 03, 2025 • Last updated 10 minutes ago • 2 minute read This image provided by the Fermi National Accelerator Laboratory shows the ring-shaped track that scientists used to study tiny particles called muons, July 20, 2023 in Batavia, Ill. Photo by Ryan Posteland/Fermi National Accelerator Laboratory / AP NEW YORK — Final results from a long-running U.S.-based experiment announced Tuesday show a tiny particle continues to act strangely — but that's still good news for the laws of physics as we know them. This advertisement has not loaded yet, but your article continues below. THIS CONTENT IS RESERVED FOR SUBSCRIBERS ONLY Subscribe now to read the latest news in your city and across Canada. Unlimited online access to articles from across Canada with one account. Get exclusive access to the Toronto Sun ePaper, an electronic replica of the print edition that you can share, download and comment on. Enjoy insights and behind-the-scenes analysis from our award-winning journalists. Support local journalists and the next generation of journalists. Daily puzzles including the New York Times Crossword. SUBSCRIBE TO UNLOCK MORE ARTICLES Subscribe now to read the latest news in your city and across Canada. Unlimited online access to articles from across Canada with one account. Get exclusive access to the Toronto Sun ePaper, an electronic replica of the print edition that you can share, download and comment on. Enjoy insights and behind-the-scenes analysis from our award-winning journalists. Support local journalists and the next generation of journalists. Daily puzzles including the New York Times Crossword. REGISTER / SIGN IN TO UNLOCK MORE ARTICLES Create an account or sign in to continue with your reading experience. Access articles from across Canada with one account. Share your thoughts and join the conversation in the comments. Enjoy additional articles per month. Get email updates from your favourite authors. THIS ARTICLE IS FREE TO READ REGISTER TO UNLOCK. Create an account or sign in to continue with your reading experience. Access articles from across Canada with one account Share your thoughts and join the conversation in the comments Enjoy additional articles per month Get email updates from your favourite authors Don't have an account? Create Account 'This experiment is a huge feat in precision,' said Tova Holmes, an experimental physicist at the University of Tennessee, Knoxville who is not part of the collaboration. The mysterious particles called muons are considered heavier cousins to electrons. They wobble like a top when inside a magnetic field, and scientists are studying that motion to see if it lines up with the foundational rulebook of physics called the Standard Model. Experiments in the 1960s and 1970s seemed to indicate all was well. But tests at Brookhaven National Laboratory in the late 1990s and early 2000s produced something unexpected: the muons weren't behaving like they should. Decades later, an international collaboration of scientists decided to rerun the experiments with an even higher degree of precision. The team raced muons around a magnetic, ring-shaped track _ the same one used in Brookhaven's experiment — and studied their signature wiggle at the Fermi National Accelerator Laboratory near Chicago. Your noon-hour look at what's happening in Toronto and beyond. By signing up you consent to receive the above newsletter from Postmedia Network Inc. Please try again This advertisement has not loaded yet, but your article continues below. The first two sets of results — unveiled in 2021 and 2023 _ seemed to confirm the muons' weird behavior, prompting theoretical physicists to try to reconcile the new measurements with the Standard Model. Now, the group has completed the experiment and released a measurement of the muon's wobble that agrees with what they found before, using more than double the amount of data compared to 2023. They submitted their results to the journal Physical Review Letters. That said, it's not yet closing time for our most basic understanding of what's holding the universe together. While the muons raced around their track, other scientists found a way to more closely reconcile their behavior with the Standard Model with the help of supercomputers. This advertisement has not loaded yet, but your article continues below. There's still more work to be done as researchers continue to put their heads together and future experiments take a stab at measuring the muon wobble — including one at the Japan Proton Accelerator Research Complex that's expected to start near the end of the decade. Scientists also are still analyzing the final muon data to see if they can glean information about other mysterious entities like dark matter. 'This measurement will remain a benchmark … for many years to come,' said Marco Incagli with the National Institute for Nuclear Physics in Italy. By wrangling muons, scientists are striving to answer fundamental questions that have long puzzled humanity, said Peter Winter with Argonne National Laboratory. 'Aren't we all curious to understand how the universe works?' said Winter. Other Sports Canada Toronto & GTA Other Sports Canada
