H. N. Brown

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.

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 ppm (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 for the negative muon. The result a(mu(-))=11 659 214(8)(3) x 10(-10) (0.7 ppm), where the first uncertainty is statistical and the second is systematic, is consistent with previous measurements of the anomaly for the positive and the negative muon. The average of the measurements of the muon anomaly is a(mu)(exp)=11 659 208(6) x 10(-10) (0.5 ppm).

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 Brookhaven muon storage ring magnet

Abstract The muon g-2 experiment at Brookhaven National Laboratory has the goal of determining the muon anomalous g-value a μ (=(g−2)/2) to the very high precision of 0.35 parts per million and thus requires a storage ring magnet with great stability and homogeniety. A superferric storage ring with a radius of 7.11 m and a magnetic field of 1.45 T has been constructed in which the field quality is largely determined by the iron, and the excitation is provided by superconducting coils operating at a current of 5200 A. The storage ring has been constructed with maximum attention to azimuthal symmetry and to tight mechanical tolerances and with many features to allow obtaining a homogenous magnetic field. The fabrication of the storage ring, its cryogenics and quench protection systems, and its initial testing and operation are described.

The superconducting inflector for the BNL g-2 experiment

The muon g-2 experiment at Brookhaven National Laboratory (BNL) has the goal of determining the muon anomalous magnetic moment, a(mu) (= (g-2)/2), to the very high precision of 0.35 parts per million and thus requires a storage ring magnet with great stability and homogeneity. A super-ferric storage ring has been constructed in which the field is to be known to 0.1 ppm. In addition, a new type of air core superconducting inflector has been developed and constructed, which successfully serves as the injection magnet. The injection magnet cancels the storage ring field, 1.5 T, seen by the entering muon beam very close to the storage ring aperture. At the same time, it gives negligible influence to the knowledge of the uniform main magnetic field in the muon storage region located at just 23 rum away from the beam channel. This was accomplished using a new double cosine theta design for the magnetic field which traps most of the return field, and then surrounding the magnet with a special superconducting sheet which traps the remaining return field. The magnet is operated using a warm-to-cold cryogenic cycle which avoids affecting the precision field of the storage ring. This article describes the design, research development, fabrication process, and final performance of this new type of superconducting magnet

A Sensitive Search for a Muon Electric Dipole Moment

Y.K. Semertzidis, H. Brown, G.T. Danby, J.W. Jackson, R. Larsen,D.M. Lazarus, W. Meng, W.M. Morse, C. Ozben, R. PriglBrookhaven National Lab, Upton, New York 11973R.M. Carey, J.P. Miller, O. Rind, B.L. Roberts, L.R. SulakDepartment of Physics, Boston University, Boston, Massachusetts 02215V. Balakin, A. Bazhan, A. Dudnikov, B.I. Khazin, G. SylvestrovBudker Institute of Nuclear Physics, Novosibirsk, RussiaY. OrlovNewman Laboratory, Cornell University, Ithaca, New York 14853K. JungmannPhysikalisches Institut der Universitat Heidelberg, 69120 Heidelberg, GermanyP.T. Debevec, D.W. Hertzog, C.J.G. OnderwaterPhysics Department, University of Illinois at Urbana-Champaign,Urbana-Champaign, Illinois 61801E.J. StephensonIndiana University Cyclotron Facility, Bloomington, Indiana 47408P. Cushman, I. KronkvistDepartment of Physics, University of Minnesota, Minneapolis, Minnesota 55455F.J.M. FarleyDepartment of Physics, Yale University, New Haven, Connecticut 06511We are proposing a new method to carry out a dedicated search for a permanent electric dipole moment (EDM) of the muon with a sensitivity at a level of 10^{-24} e cm. The experimental design exploits the strong motional electric field sensed by relativistic particles in a magnetic storage ring. As a key feature, a novel technique has been invented in which the g-2 precession is compensated with radial electric field. This technique will benefit greatly when the intense muon sources advocated by the developers of the muon storage rings and the muon colliders become available.

New Results from the Muon g ‐ 2 Experiment

The Muon g ‐ 2 collaboration has measured the anomalous magnetic g value, a = (g ‐ 2)/2, of the positive muon with an unprecedented uncertainty of 0.7 parts per million. The result aμ+(expt)u2009=u200911659204(7)(5)u2009×u200910−10, based on data collected in the year 2000 at Brookhaven National Laboratory, is in good agreement with the preceeding data on aμ+ and aμ−. The measurement tests standard model theory, which at the level of the current experimental uncertainty involves quantum electrodynamics, quantum chromodynamics, and electroweak interaction in a significant way.

Measurement of the muon (g-2)-value

The muon (g - 2) experiment is described, and the recent results are presented. These results represent the final measurement for the positive muon.