Twenty years after an apparent anomaly in the behavior of elementary particles raised hopes of a major physics breakthrough, a new measurement has solidified them: Physicists at Fermi National Accelerator Laboratory near Chicago
announced today that muons — elementary particles similar to electrons — wobbled more than expected while whipping around a magnetized ring.
The widely anticipated new measurement confirms the decades-old result, which made headlines around the world. Both measurements of the muon’s wobbliness, or magnetic moment, significantly overshoot the theoretical prediction, as
calculated last year by an international consortium of 132 theoretical physicists. The Fermilab researchers estimate that the difference has grown to a level quantified as “4.2 sigma,” well on the way to the stringent five-sigma level that physicists need to claim a discovery.
