Measurement of the muon anomaly to high and even higher precision

Abstract

Our recent series of measurements at Brookhaven National Laboratory determined the muon anomalous magnetic moment \amu to a precision of 0.5 ppm. The final result--representing the average of five running periods using both positive and negative muons--is $\amu ^\pm = 11 659 208(6) \times 10^{-10}$. It lies 2.7 standard deviations above the standard model expectation, which is based on updates given at this Workshop. Importantly, only the $e^{+}{e}^{-}$ annihilation and new KLOE radiative return data are used for the hadronic vacuum polarization input. Because the systematic limit has not been reached in the experiment, a new effort has been proposed and approved with the highest scientific priority at Brookhaven. The goal is an experimental uncertainty of 0.2 ppm, a 2.5-fold reduction in the overall experimental uncertainty. To do so will require a suite of upgrades and several qualitative changes in the philosophy of how the measurement is carried out. I discuss the old and new experiments with a particular emphasis on the technical matters that require change for the future.

10 pages, Proceedings of the 8th International Workshop on Tau-Lepton Physics

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• Electromagnetic and Weak Moments of the Tau-Lepton
• Why do we need the new BNL muon g-2 experiment now?
• OPE Constraints and the Leading Order Hadronic Contribution to (g-2)_mu