Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm



Abi, B, Albahri, T, Al-Kilani, S, Allspach, D, Alonzi, LP, Anastasi, A, Anisenkov, A, Azfar, F, Badgley, K, Baessler, S
et al (show 226 more authors) (2021) Measurement of the Positive Muon Anomalous Magnetic Moment to 0.46 ppm. PHYSICAL REVIEW LETTERS, 126 (14). 141801-.

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Abstract

We present the first results of the Fermilab National Accelerator Laboratory (FNAL) 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 ω[over ˜]_{p}^{'} in a spherical water sample at 34.7 °C. The ratio ω_{a}/ω[over ˜]_{p}^{'}, 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 Brookhaven National Laboratory (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.

Item Type: Article
Additional Information: 10 pages; 4 figures
Uncontrolled Keywords: Muon <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>g</mi><mo>−</mo><mn>2</mn></math> Collaboration
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 13 Apr 2021 07:11
Last Modified: 18 Jan 2023 22:53
DOI: 10.1103/PhysRevLett.126.141801
Open Access URL: https://journals.aps.org/prab/pdf/10.1103/PhysRevA...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3119133