The Muon Anomaly: Experiment and Theory

A summary is given of the present status of the theory and experiment of the anomalous magnetic moment of the muon. A difference between predicted and measured values is an indication of physics beyond the Standard Model. A new experimental measurement has produced a value which differs from a recent Standard Model prediction by 2.6 standard deviations. The experimental number differs from other recent theoretical predictions, based on different evaluations of the hadronic contribution, by at least 2 standard deviations in every case. Additional data are being analyzed and the theory is being scrutinized to see if this discrepancy will be sustained.