121 research outputs found
Measurement of the Negative Muon Anomalous Magnetic Moment to 0.7 ppm
The anomalous magnetic moment of the negative muon has been measured to a
precision of 0.7 parts per million (ppm) at the Brookhaven Alternating Gradient
Synchrotron. This result is based on data collected in 2001, and is over an
order of magnitude more precise than the previous measurement of the negative
muon. The result a_mu= 11 659 214(8)(3) \times 10^{-10} (0.7 ppm), where the
first uncertainty is statistical and the second is sytematic, is consistend
with previous measurements of the anomaly for the positive and negative muon.
The average for the muon anomaly a_{mu}(exp) = 11 659 208(6) \times 10^{-10}
(0.5ppm).Comment: 4 pages, 4 figures, submitted to Physical Review Letters, revised to
reflect referee comments. Text further revised to reflect additional referee
comments and a corrected Fig. 3 replaces the older versio
Search for Lorentz and CPT Violation Effects in Muon Spin Precession
The spin precession frequency of muons stored in the storage ring has
been analyzed for evidence of Lorentz and CPT violation. Two Lorentz and CPT
violation signatures were searched for: a nonzero
(=); and a sidereal variation of
. No significant effect is found, and the following
limits on the standard-model extension parameters are obtained: GeV; GeV; and the 95% confidence level limits
GeV and
GeV.Comment: 5 pages, 3 figures, submitted to Physical Review Letters, Modified to
answer the referees suggestion
An Improved Limit on the Muon Electric Dipole Moment
Three independent searches for an electric dipole moment (EDM) of the
positive and negative muons have been performed, using spin precession data
from the muon g-2 storage ring at Brookhaven National Laboratory. Details on
the experimental apparatus and the three analyses are presented. Since the
individual results on the positive and negative muon, as well as the combined
result, d=-0.1(0.9)E-19 e-cm, are all consistent with zero, we set a new muon
EDM limit, |d| < 1.9E-19 e-cm (95% C.L.). This represents a factor of 5
improvement over the previous best limit on the muon EDM.Comment: 19 pages, 15 figures, 7 table
Search for Lorentz and CPT Violation Effects in Muon Spin Precession
The spin precession frequency of muons stored in the storage ring has
been analyzed for evidence of Lorentz and CPT violation. Two Lorentz and CPT
violation signatures were searched for: a nonzero
(=); and a sidereal variation of
. No significant effect is found, and the following
limits on the standard-model extension parameters are obtained: GeV; GeV; and the 95% confidence level limits
GeV and
GeV.Comment: 5 pages, 3 figures, submitted to Physical Review Letters, Modified to
answer the referees suggestion
The Muon Anomalous Magnetic Moment and the Standard Model
The muon anomalous magnetic moment measurement, when compared with theory,
can be used to test many extensions to the standard model. The most recent
measurement made by the Brookhaven E821 Collaboration reduces the uncertainty
on the world average of a_mu to 0.7 ppm, comparable in precision to theory.
This paper describes the experiment and the current theoretical efforts to
establish a correct standard model reference value for the muon anomaly.Comment: Plenary Talk; PANIC'02 XVI Particles and Nuclear International
Conference, Osaka, Japan; Sept. 30 - Oct. 4, 2002; Report describes the
published 0.7 ppm result and updates the theory statu
Final Report of the Muon E821 Anomalous Magnetic Moment Measurement at BNL
We present the final report from a series of precision measurements of the
muon anomalous magnetic moment, a_mu = (g-2)/2. The details of the experimental
method, apparatus, data taking, and analysis are summarized. Data obtained at
Brookhaven National Laboratory, using nearly equal samples of positive and
negative muons, were used to deduce a_mu(Expt) = 11 659 208.0(5.4)(3.3) x
10^-10, where the statistical and systematic uncertainties are given,
respectively. The combined uncertainty of 0.54 ppm represents a 14-fold
improvement compared to previous measurements at CERN. The standard model value
for a_mu includes contributions from virtual QED, weak, and hadronic processes.
While the QED processes account for most of the anomaly, the largest
theoretical uncertainty, ~0.55 ppm, is associated with first-order hadronic
vacuum polarization. Present standard model evaluations, based on e+e- hadronic
cross sections, lie 2.2 - 2.7 standard deviations below the experimental
result.Comment: Summary paper of E821 Collaboration measurements of the muon
anomalous magnetic moment, each reported earlier in Letters or Brief Reports;
96 pages, 41 figures, 16 tables. Revised version submitted to PR
Improved Measurement of the Positive Muon Anomalous Magnetic Moment
A new measurement of the positive muon's anomalous magnetic moment has been
made at the Brookhaven Alternating Gradient Synchrotron using the direct
injection of polarized muons into the superferric storage ring. The angular
frequency difference omega_{a} between the angular spin precession frequency
omega_{s} and the angular orbital frequency omega_{c} is measured as well as
the free proton NMR frequency omega_{p}. These determine
R = omega_{a} / omega_{p} = 3.707~201(19) times 10^{-3}. With mu_{mu} /
mu_{p} = 3.183~345~39(10) this gives a_{mu^+} = 11~659~191(59) times 10^{-10}
(pm 5 ppm), in good agreement with the previous CERN and BNL measurements for
mu^+ and mu^-, and with the standard model prediction.Comment: 4 pages, 4 figures. accepted for publication in Phys. Rev. D62 Rapid
Communication
News from the Muon (g-2) Experiment at BNL
The magnetic moment anomaly a_mu = (g_mu - 2) / 2 of the positive muon has
been measured at the Brookhaven Alternating Gradient Synchrotron with an
uncertainty of 0.7 ppm. The new result, based on data taken in 2000, agrees
well with previous measurements. Standard Model evaluations currently differ
from the experimental result by 1.6 to 3.0 standard deviations.Comment: Talk presented at RADCOR - Loops and Legs 2002, Kloster Banz,
Germany, September 8-13 2002, to be published in Nuclear Physics B (Proc.
Suppl.); 5 pages, 3 figure
A new approach for measuring the muon anomalous magnetic moment and electric dipole moment
This paper introduces a new approach to measure the muon magnetic moment anomaly a?? = (g - 2)/2 and the muon electric dipole moment (EDM) d?? at the J-PARC muon facility. The goal of our experiment is to measure a?? and d?? using an independent method with a factor of 10 lower muon momentum, and a factor of 20 smaller diameter storage-ring solenoid compared with previous and ongoing muon g - 2 experiments with unprecedented quality of the storage magnetic field. Additional significant differences from the present experimental method include a factor of 1000 smaller transverse emittance of the muon beam (reaccelerated thermal muon beam), its efficient vertical injection into the solenoid, and tracking each decay positron from muon decay to obtain its momentum vector. The precision goal for a?? is a statistical uncertainty of 450 parts per billion (ppb), similar to the present experimental uncertainty, and a systematic uncertainty less than 70 ppb. The goal for EDM is a sensitivity of 1.5 ?? 10-21 ecm
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