Does the latest measurement of the muon hint at new physics?

Two years ago, physicists confirmed that a subatomic particle called the muon was slightly more magnetic than predicted by the standard model, the theory that describes fundamental particles and their interactions. The find raised hopes that scientists might finally be seeing signs of something beyond the standard model that would reinvigorate particle physics. Now, the same team has reported a new measurement of the muon’s magnetism that’s twice as precise as the previous one. But whether the finding challenges the standard model remains unclear. That’s not because the new measurement doesn’t agree with the previous one (it does), but because, ironically, the standard model prediction for the muon’s magnetism look less certain that it did 2 years ago. “It’s a fantastic result,” says Aida El-Khadra, a theoretical physicist at the University of Illinois Urbana-Champaign who was not involved in the experiment. Still, she says, given the greater uncertainties in the standard model prediction, it’s impossible to say what the finding implies. “Theory has to get its act together.” Common in cosmic rays, the muon is a heavier cousin of the electron. It can be blasted into fleeting existence in particle collisions. Because it is electrically charged, the particle goes in circles when it whizzes through a magnetic field. At the same time, the muon is magnetized like a little compass needle. Even as it circles, the magnetic field will m...
Source: ScienceNOW - Category: Science Source Type: news