3,748 research outputs found
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 from
Brookhaven E821 by a factor of 4; that is, , 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
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