Status of the Fermilab Muon $g-2$ Experiment

TL;DR

The Fermilab Muon g-2 experiment measures the muon's magnetic moment with high precision, confirming a discrepancy with the Standard Model prediction that could indicate new physics.

Contribution

This paper reports on the experimental setup and current status of the Fermilab Muon g-2 experiment, including recent measurements and their implications.

Findings

Measurement of $a_$ with 0.46 ppm precision

Confirmation of the 4.2 sigma discrepancy with the SM

Ongoing efforts to improve experimental accuracy

Abstract

The muon anomalous magnetic moment, $a_\mu = (g-2)/2$, is a low-energy observable which can be both measured and computed with very high precision, making it an excellent test of the Standard Model (SM) and a sensitive probe of new physics. Recent efforts improved the precision of both the theoretical prediction and the experimental measurement. On the theory side, the Muon $g-2$ Theory Initiative, an international team of more than 130 physicists, reached in 2020 a consensus on the SM prediction for $a_\mu$. On the experimental side, the E989 Muon $g-2$ Collaboration at Fermilab (FNAL) published in April 2021 a new measurement of $a_\mu$ from the Run-1 dataset (2018) with 0.46 ppm precision, corroborating the previous Brookhaven National Laboratory (BNL) measurement and increasing the discrepancy with the SM value to 4.2 standard deviations. In this paper, I will discuss the experimental setup and report on the current status of the experiment.