Measurement of the Positive Muon Anomalous Magnetic Moment to 0.20 ppm
Abstract
We present a new measurement of the positive muon magnetic anomaly,
aμ ≡ (gμ − 2) /2,
from the Fermilab Muon g − 2 Experiment using data collected in
2019 and 2020. We have analyzed more than 4 times the number of positrons from
muon decay than in our previous result from 2018 data. The systematic error is
reduced by more than a factor of 2 due to better running conditions, a more stable
beam, and improved knowledge of the magnetic field weighted by the muon
distribution,
ωp',
and of the anomalous precession frequency corrected for beam
dynamics effects, ωa. From the ratio
ωa /ωp',
together with precisely determined external parameters, we determine
aμ = 116 592 057(25) × 10−11
(0.21 ppm).
Combining this result with our previous result from the 2018 data, we obtain
aμ (FNAL) = 116 592 055(24) × 10−11
(0.20 ppm). The new experimental world average is
aμ (exp) = 116 592 059(22) × 10−11
(0.19 ppm), which represents a factor of 2 improvement in precision.
Muon g-2 Collaboration,
Physical Review Letters, 131 (2023) 161802.
DOI: 10.1103/PhysRevLett.131.161802
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