M. Kawamura

Final report of the E821 muon 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)=11659208.0(5.4)(3.3)x10(-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, approximate to 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.

Precise Measurement of the Positive Muon Anomalous Magnetic Moment

A precise measurement of the anomalous g value, a(mu) = (g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. The result a(mu+) = 11 659 202(14) (6) x 10(-10) (1.3 ppm) is in good agreement with previous measurements and has an error one third that of the combined previous data. The current theoretical value from the standard model is a(mu)(SM) = 11 659 159.6(6.7) x 10(-10) (0.57 ppm) and a(mu)(exp) - a(mu)(SM) = 43(16) x 10(-10) in which a(mu)(exp) is the world average experimental value.

Improved limit on the muon electric dipole moment

G.W. Bennett, B. Bousquet, H.N. Brown, G. Bunce, R.M. Carey, P. Cushman, G.T. Danby, P.T. Debevec, M. Deile, H. Deng, W. Deninger, S.K. Dhawan, V.P. Druzhinin, L. Duong, E. Efstathiadis, F.J.M. Farley, G.V. Fedotovich, S. Giron, F.E. Gray, D. Grigoriev, M. Grosse-Perdekamp, A. Grossmann, M.F. Hare, D.W. Hertzog, X. Huang, V.W. Hughes, M. Iwasaki, K. Jungmann, D. Kawall, M. Kawamura, B.I. Khazin, J. Kindem, F. Krienen, I. Kronkvist, A. Lam, R. Larsen, Y.Y. Lee, I. Logashenko, R. McNabb, W. Meng, J. Mi, J.P. Miller, Y. Mizumachi, W.M. Morse, D. Nikas, C.J.G. Onderwater, Y. Orlov, C.S. Özben, J.M. Paley, Q. Peng, C.C. Polly, J. Pretz, R. Prigl, G. zu Putlitz, T. Qian, S.I. Redin, O. Rind, B.L. Roberts, N. Ryskulov, S. Sedykh, Y.K. Semertzidis, P. Shagin, Yu.M. Shatunov, E.P. Sichtermann, E. Solodov, M. Sossong, A. Steinmetz, L.R. Sulak, C. Timmermans, A. Trofimov, D. Urner, P. von Walter, D. Warburton, D. Winn, A. Yamamoto and D. Zimmerman (Muon (g − 2) Collaboration) Department of Physics, Boston University, Boston, MA 02215 Brookhaven National Laboratory, Upton, NY 11973 Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia LEPP, Cornell University, Ithaca, NY 14853 Fairfield University, Fairfield, CT 06430 6 Kernfysisch Versneller Instituut, University of Groningen, NL-9747 AA, Groningen, The Netherlands 7 Physikalisches Institut der Universität Heidelberg, 69120 Heidelberg, Germany 8 Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801 9 KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan Department of Physics, University. of Minnesota., Minneapolis, MN 55455 11 Science University of Tokyo, Tokyo, 153-8902, Japan 12 Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551, Japan 13 Department of Physics, Yale University, New Haven, CT 06520 † Deceased

Improved measurement of the positive muon anomalous magnetic moment

A new measurement of the positive muons 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 MMR frequency omega (p). These determine R = omega (a)/omega (p) = 3.707 201(19) x 10(-3). With mu (mu)/mu (p) = 3.183 345 39(10) this gives a(mu+) = 11 659 191(59) x 10-(10) (+/-5 ppm), in good agreement with the previous CERN and BNL measurements for mu (+) and mu (-), and with the standard model prediction.

The muon anomalous magnetic moment

The muon g-2 experiment at the Brookhaven National Laboratory is described, including its motivation, goal and present status. The latest result based on 1998 data is aμ+=g−2/2=11 659 191(59)×10−10 (5 ppm), where the error is primarily statistical. This value agrees with the present theoretical value. Data obtained thus far and now being analyzed should have a statistical error of about 0.5 ppm.

Muon g-2 experiment at Brookhaven National Laboratory

By the end of an excellent data taking in 1999, we collected ≈ 1 billion decay positrons with energy greater than 2 GeV and 30 μs after injection. The analysis of the 1999 data set were performed in parallel by various teams in the collaboration and each team provides a different approach to the analysis. The projected errors are expected to be of order 1.3 ppm statistical and below 0.5 ppm systematic. The data obtained in the 2000 run contains ≈ 4 times more decay positrons compared to 1999.

Testing CPT and Lorentz invariance with the anomalous spin precession of the muon

This article discusses tests of CPT and Lorentz invariance with data from the muon g-2 experiment at Brookhaven National Laboratory. According to an extension of the Standard Model by Kostelecky et al., CPT/Lorentz violating terms in the Lagrangian induce a shift of the anomaly frequency omega_a of muons in a magnetic field. This shift is predicted to be different for positive and negative muons and to oscillate with the Earths sidereal frequency. We discuss the sensitivity of the g-2 experiment to different parameters of this Standard Model extension and propose an analysis method to search for sidereal variations of omega_a.

Precision measurement of the muon anomalous magnetic moment

The Muon g − 2 collaboration has measured the anomalous magnetic g value of the positive muon with an uncertainty of 1.3 parts per million. The result aμ+(expt) = 11659202(14)(6) × 10−10, based on data collected in 1999 at Brookhaven National Laboratory, is in good agreement with the preceding data on aμ+ and aμ−, and improves the combined uncertainty by a factor of about three. The analysis of data collected in 2000 and 2001 is well underway and, when combined with data from a requested, final run in the fall of 2002 and winter of 2003, is expected to further improve the experimental uncertainty by a factor of about three to 0.4ppm. The measurement tests standard theory and has the potential to discover new physics.

Recent results from the BNL g-2 experiment

Abstract The status of the muon g — 2 experiment at the AGS facility of Brookhaven National Laboratory is discussed. Data obtained in 1999 with positive muons has been analyzed and published. The final data set contained 0.95 × 10 9 events and had an accuracy of 1.3 ppm . Approximately four times more data with positive muons and three times more data with negative muons were obtained in 2000 and 2001, respectively. These data were obtained with a more uniform magnetic field and with different storage ring tunes. An accuracy of the order of 0.5 ppm is anticipated.