Measurement of the muon magnetic anomaly $a_\mu$ in the Muon $g-2$ experiment at Fermilab

Abstract

The Fermilab Muon $g-2$ experiment measures the muon anomalous magnetic moment with high precision. Together with recent improvements on the theory front, the first results of the experiment confirm the long-standing discrepancy between the experimental measurements and the Standard Model predictions. The observed value of $a_\mu({\rm FNAL}) = 116\,592\,040(54) \times 10^{-11} ~ (\text{0.46\,ppm})$, combined with the previous experimental measurement, results in a discrepancy of $ (251 \pm 59)\times 10^{-11}$ with the theoretical prediction, corresponding to $4.2 ~\sigma$. This note presents the first results, the current status and the future prospects of the Muon g-2 experiment at Fermilab.