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The strength of the magnetic field of subatomic particles.

Muon's magnetic moment

The artist’s conception of the mystery of the magnetic moment of muon, a subatomic particle similar to But heavier than electrons. (Denoted by the Greek letter mu) New muon magnetic field strength estimation closes the gap between theory and experimental measurements, making it consistent with the standard model of particle physics.Credits: Dani Zemba, Penn State.

New estimates of the magnetic field strength of subatomic particles are consistent with the standard model of particle physics.

New estimation of the magnetic field strength around muons, a subatomic particle similar to But heavier, the electrons close the gap between theory and experimental measurements, making it consistent with the standard model with the leading particles. Physics for decades

An article describing the research by an international team of scientists appears today (7 April 2021) in the journal. nature.

Twenty years ago, in an experiment at Brookhaven National Laboratory, physicists detected what appeared to be mismatched during the measurements. Mion’s “magnetic moment” – the strength of the magnetic field and the theoretical calculation of what the measurement should be. The possibility of undiscovered particles or physical forces. New discoveries reduce this discrepancy, suggesting that Moon’s magnetic power is unlikely to be a mystery. To achieve this, instead of relying on experimental data, the researchers simulated every aspect of computing from the ground up, a task that required very high computing power.

“Most of the phenomena in nature can be explained by what we call the“ natural phenomenon ”. “The standard model” of particle physics, “said Zoltan Fodor, Penn State physics professor and lead research team leader,” we can predict the properties of particles very accurately based solely on this theory. We are excited that we may find something new that goes beyond the standard model. ”

For the discovery of new physics beyond the standard model, there was a consensus among physicists that the conflict between theory and measure would require five sigma values, a statistical measure equal to approximately 1 in 3.5 probability. million

In the case of Miwon, the measurement of the magnetic field deviates from the existing theoretical predictions of about 3.7 sigma, interesting, but not enough to announce the discovery of a new break-up of the laws of physics. Therefore, the researchers aim to improve both the measurement and the theory, hoping to bring the theory and measure to impact each other, or raise the sigma to a level that will allow announcements of new physics discoveries.

“The existing theory for estimating the magnetic field strength of Muon relies on an experimental measure of electron-positron destruction,” Fodor said. Totally independent of dependence on experimental measurements We start with the fundamental equation and build all estimates from scratch. “

The new computation required hundreds of millions of CPU hours at several supercomputer centers in Europe and brought the theory back in line with measurements. However, the story is not over yet. A new, more accurate measurement of muon’s magnetic momentum is expected very soon.

“If our calculations are correct and the new measurements don’t change the story, it seems that we don’t need new physics to explain the miwon’s magnetic moment – it follows the rules of the standard model,” Fodor said. The expectations for new physics will always be attractive. But it’s also exciting to see the theory and the experiment go hand in hand. It deepens our understanding and opens up new possibilities for exploration. ”

The excitement was out of reach.

“Our results should be cross-checked by other groups, and we expect them,” Fodor said. “In addition, our findings mean there is tension between our previous theoretical results and our new results. This discrepancy should be understood. In addition, the new results may be closer to the old results or the earlier theoretical calculations. We have a lot of excitement ahead. “

Reference: “Leading Hadronic Contribution to the Magnetic Momon Moment from lattice QCD” by Sz Borsanyi, Z. Fodor, JN Guenther, C. Hoelbling, SD Katz, L. Lellouch, T. Lippert, K.Miura, L. Parato, KK Szabo, F.Stokes, BC Toth, Cs. Torok and L. Varnhorst April 7, 2021. nature.
DOI: 10.1038 / s41586-021-03418-1

In addition to Fodor, the research team included Szabolcs Borsanyi, Jana N. Guenther, Christian Hoelbling, Sandor D. Katz, Laurent Lellouch, Thomas Lippert, Laurent Lellouch, Kohtaroh Miura, Letizia Parato, Kalman K. Szabo, Finn Stokes, Balint C. Toth, Csaba Torok, Lukas Varnhorst.

Participating institutions are Penn State, University of Wuppertal in Germany; Jülich Supercomputing Center in Germany; Eötvös University in Budapest, Hungary; University of California, San Diego; The University of Regensburg in Germany; Aix Marseille Univ, Université de Toulon in Marseille, France; Helmholtz Institute Mainz in Germany; Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University in Japan

The research was funded by the German Research Foundation (DFG); German Federal Ministry of Education and Research (BMBF); Hungarian National Research, Development and Innovation Agency And the Excellence Initiative of Aix-Marseille Which is a French investment program through the Chaire d’Excellence and Laboratoire d’Excellence programs.

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