We present a new measurement of the positive muon magnetic anomaly, a µ ≡ (gµ − 2)/2, from the Fermilab Muon g −2 Experiment based on data collected in 2019 and 2020. We have analyzed more than four 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 two due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, ω′ p , and of the anomalous precession frequency corrected for beam dynamics effects, ωa. From the ratio ωa/ω ′ p , together with precisely determined external parameters, we determine a µ = 116 592 057(25) × 10 −11 (0.21 ppm). Combining this result with our previous result from the 2018 data, we obtain a µ (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 two improvement in precision.

The cryogenic storage ring CSR Review of Scientific Instruments 87, 063115 (2016); https://doi

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We propose using the storage ring electric dipole moment (EDM) method to search for the axion dark matter induced EDM oscillation in nucleons. The method uses a combination of B and E fields to produce a resonance between the g − 2 spin precession frequency and the background axion field oscillation to greatly enhance sensitivity to it. An axion frequency range from 10 −9 Hz to 100 MHz can, in principle, be scanned with high sensitivity, corresponding to an f a range of 10 13 GeV ≤ f a ≤ 10 30 GeV, the breakdown scale of the global symmetry generating the axion or axionlike particles.