Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm

Abstract

We present the first results of the Fermilab Muon g-2 Experiment for the positive muon magnetic anomaly a μ ≡ (g μ - 2)/2. The anomaly is determined from the precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency ω a between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring. The storage ring magnetic field is measured using nuclear magnetic resonance probes calibrated in terms of the equivalent proton spin precession frequency $\\tilde{ω}$ p 0 in a spherical water sample at 34.7 deg C. The ratio ω a /$\\tilde{ω}$ p 0 , together with known fundamental constants, determines a μ (FNAL) = 116 592 040(54) × 10 -11 (0.46 ppm). The result is 3.3 standard deviations greater than the Standard Model prediction and is in excellent agreement with the previous BNL E821 measurement. After combination with previous measurements of both μ + and μ - , the new experimental average of a μ (Exp) = 116 592 061(41)×10 -11 (0.35 ppm) increases the tension between experiment and theory to 4.2 standard deviations.

Keywords

Affiliated Institutions

• Regis University US
• Argonne National Laboratory US
• University of Udine IT
• University of Virginia US
• University of Kentucky US
• Brookhaven National Laboratory US
• National Institute of Optics IT
• University College London GB
• University of Liverpool GB
• Northern Illinois University US
• University of Oxford GB
• Fermi National Accelerator Laboratory US
• Boston University US
• Istituto Nazionale di Fisica Nucleare, Roma Tor Vergata IT
• Michigan State University US
• North Central College US
• Istituto Nazionale di Fisica Nucleare, Sezione di Trieste IT
• University of Illinois Urbana-Champaign US
• University of Massachusetts Amherst US
• Institute for Basic Science KR
• Università degli studi di Cassino e del Lazio Meridionale IT
• Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati IT
• Budker Institute of Nuclear Physics RU
• University of Michigan US
• Johannes Gutenberg University Mainz DE
• University of Pisa IT
• University of Trieste IT
• James Madison University US
• Istituto Nazionale di Fisica Nucleare, Sezione di Napoli IT
• University of Washington US
• Cornell University US
• University of Mississippi US
• Joint Institute for Nuclear Research RU
• Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Udine
• University of Molise IT
• Istituto Nazionale di Fisica Nucleare, Sezione di Pisa IT
• Korea Advanced Institute of Science and Technology KR
• Lancaster University GB
• Shanghai Jiao Tong University CN

Related Publications