Fermilab G-2 Collaboration Publishes Final Result
PiMuNu writes:
Physics reports that Fermilab's g-2 collaboration has now published its final result.
https://physics.aps.org/articles/v18/116
After measuring the wobbles of 300 billion muons, the Muon g - 2 Collaboration has pinpointed with exquisite precision the internal magnetism of these subatomic particles. The muon's magnetic strength, or moment, has animated particle physics research over the past two decades, as experiment and theory appeared to disagree over its value-raising a flag for possible new physics. In a somewhat surprising turn of events, the final results from the Muon g - 2 experiment line up with the most recent predictions, further validating the standard model of particle physics.
The muon-the heavy cousin to the electron-started to grab the particle-physics spotlight in the 1990s when an experiment at Brookhaven National Laboratory in New York reported the first hints that the muon's magnetic behavior might not match predictions based on the standard model, which has otherwise been widely successful in explaining the subatomic world. The Brookhaven measurements involved magnetically trapping muons in a circular ring and observing how much their internal magnet, or "spin," wobbled around an applied magnetic field. To further investigate this discrepancy, the experiment's big magnet was moved cross-country in 2013 to Fermi National Laboratory (Fermilab) in Illinois. The first results from the transplanted Muon g - 2 experiment came out in 2021, showing good agreement with the Brookhaven findings and raising the significance of the discrepancy (see Viewpoint: Muon's Escalating Challenge to the Standard Model).
The discrepancy has apparently been resolved following improvements to the theoretical estimate for g-2. The Standard Model of Particle Physics - disappointingly for particle physicists - still stands as an entirely accurate prediction of almost all of subatomic physics (the exception being neutrino oscillations https://en.wikipedia.org/wiki/Neutrino_oscillation ).
Preprint paper:
http://arxiv.org/abs/2506.03069
Previously:
g-2 Releases New Data
Making Sense of the Muon's Misdemeanours
Muon G-2 Experiment Hints at Mysterious New Physics
Latest Muon Measurements Hint at Cracks in the Standard Model
The Cloak-and-Dagger Tale Behind This Year's Most Anticipated Result in Particle Physics
Precision Measurements of the Standard Model
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