W.K.H. Panofsky Prize in Experimental Particle Physics - Bradley Roberts: Forty-four years of measuring the muon magnetic moment: 1957 – 2001. What have we learned?

Measurements of the muon magnetic moment have played an important role in the development of the Standard Model. Simultaneous with the discovery of parity non-conservation in beta decay, it was also observed in muon decay by two famous experiments. The parity violating pion decay produces polarized muons and the parity violating muon decay provides the information needed to study the muon magnetic moment as explained by T.D. Lee and C.N. Yang. The first muon spin rotation experiment at the Columbia Nevis cyclotron observed parity violation and also determined that the g value of the muon was consistent with the Dirac value of 2. Further work at Nevis demonstrated that the muon magnetic anomaly, a_m = (g_m-2)/2, was consistent with a/2p, viz. in a magnetic field the muon behaved like a heavy electron. I will discuss the history of the measurements of the muon anomaly leading up to the Brookhaven National Lab g-2 experiment, E821, and discuss what needed to be improved to reach the BNL precision goal of a factor of twenty better than the final CERN experiment.