The BNL Muon Anomalous Magnetic Moment Measurement

The E821 experiment at Brookhaven National Laboratory is designed to measure the muon magnetic anomaly, a_mu, to an ultimate precision of 0.4 parts per million (ppm). Because theory can predict a_mu to 0.6 ppm, and ongoing efforts aim to reduce this uncertainty, the comparison represents an important and sensitive test of new physics. At the time of this Workshop, the reported experimental result from the 1999 running period achieved a_mu = 11 659 202(14)(6)x 10^-10 (1.3 ppm) and differed from the most precise theory evaluation by 2.6 standard deviations. Considerable additional data has already been obtained in 2000 and 2001 and the analysis of this data is proceeding well. Intense theoretical activity has also taken place ranging from suggestions of the new physics which could account for the deviation to careful re-examination of the standard model contributions themselves. Recently, a re-evaluation of the pion pole contribution to the hadronic light-by-light process exposed a sign error in earlier studies used in the standard theory. With this correction incorporated, experiment and theory disagree by a modest 1.6 standard deviations.Comment: To be published in the Proceedings of the Workshop on Electromagnetic Probes of Fundamental Physics, Erice, 16 - 21 October 2001 (On behalf of the Brookhaven E821 Collaboration) Uses 13 ps/eps figures. 14 pages tota

Next Generation Muon g-2 Experiments

I report on the progress of two new muon anomalous magnetic moment experiments, which are in advanced design and construction phases. The goal of Fermilab E989 is to reduce the experimental uncertainty of $a_\mu$ from Brookhaven E821 by a factor of 4; that is, $\delta a_\mu \sim 16 \times 10^{-11}$, a relative uncertainty of 140~ppb. The method follows the same magic-momentum storage ring concept used at BNL, and pioneered previously at CERN, but muon beam preparation, storage ring internal hardware, field measuring equipment, and detector and electronics systems are all new or upgraded significantly. In contrast, J-PARC E34 will employ a novel approach based on injection of an ultra-cold, low-energy, muon beam injected into a small, but highly uniform magnet. Only a small magnetic focusing field is needed to maintain storage, which distinguishes it from CERN, BNL and Fermilab. E34 aims to roughly match the previous BNL precision in their Phase~1 installation.Comment: 8 pages, 5 figures, 2 tables, Invited talk given at the FCCP 2015 Worksho

Games of status and discriminatory contracts

Following recent empirical evidence which indicates the importance of rank for the determination of workers' wellbeing, this paper introduces status seeking preferences in the form of rank-dependent utility functions into a moral hazard framework with one firm and multiple workers, but no correlation in production. We show that workers' concern for the rank of their wage in the firm's wage distribution induces the firm to offer discriminatory wage contracts when its aim is to induce all workers to expend effort

Why do we need the new BNL muon g-2 experiment now?

New final results from the CMD-2 and SND e+e- annihilation experiments, together with radiative return measurements from BaBar, lead to recent improvements in the standard model prediction for the muon anomaly. The uncertainty at 0.48 ppm--a largely data-driven result--is now slightly below the experimental uncertainty of 0.54 ppm. The difference, a_mu(expt)- a_mu(SM) = (27.6 +/- 8.4) x 10^-10, represents a 3.3 standard deviation effect. At this level, it is one of the most compelling indicators of physics beyond the standard model and, at the very least, a major constraint for speculative new theories such as SUSY or extra dimensions. Others at this Workshop detailed further planned standard model theory improvements to a_mu. Here I outline how BNL E969 will achieve a factor of 2 or more reduction in the experimental uncertainty. The new experiment is based on a proven technique and track record. I argue that this work must be started now to have maximal impact on the interpretation of the new physics anticipated to be unearthed at the LHC.Comment: Invited Talk, Tau-06 Workshop, 10 pages, 5 figure