2004/01/31 by G. W. Bennett, B. Bousquet, H. Brown +59 · 2 citations
Engineering · Physics and Astronomy · #Particle physics theoretical and experimental studies #Scientific Research and Discoveries #Superconducting Materials and Applications #hep-ex
paper · pdf · doi:10.1103/physrevlett.92.161802
published as Phys.Rev.Lett.92:161802,2004 · 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 version
arxiv created 2004/02/21 · openalex publication_date 2004/04/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present the first results of the Fermilab National Accelerator Laboratory (FNAL) Muon g-2 Experiment for the positive muon magnetic anomaly aμ≡(gμ-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 ωa 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 ω[over ˜]p' in a spherical water sample at 34.7 °C. The ratio ωa/ω[over ˜]p', together with known fundamental constants, determines aμ(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 Brookhaven National Laboratory (BNL) E821 measurement. After combination with previous measurements of both μ+ and μ-, the new experimental average of aμ(Exp)=116 592 061(41)×10-11 (0.35 ppm) increases the tension between experiment and theory to 4.2 standard deviations.