Measurement of the positive muon anomalous magnetic moment to 0.20 ppm

We present a new measurement of the positive muon magnetic anomaly, a_\mu = \frac{g_\mu-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, \omega_p′, and of the anomalous precession frequency corrected for beam dynamics effects, \omega_a. From the ratio \omega_a/\omega_p′, together with precisely determined external parameters, we determine a_\mu=116 592 057(25)×10^{-11} (0.21 ppm). Combining this result with our previous result from the 2018 data, we obtain a_\mu(FNAL)=116 592 055(24)×10^{-11} (0.20 ppm). The new experimental world average is a_\mu(exp)=116 592 059(22)×10^{-11} (0.19 ppm), which represents a factor of 2 improvement in precision.