The muon $g$-$2$ experiment at Fermilab

TL;DR

The Fermilab muon $g$-$2$ experiment aims to precisely measure the muon's anomalous magnetic moment, potentially confirming deviations from the standard model and indicating new physics beyond current theories.

Contribution

This paper details the design, upgrades, and expected precision of the Fermilab $g$-$2$ experiment, which improves measurement accuracy over previous efforts.

Findings

Enhanced measurement precision to 140 ppb.

Potential to observe >7$\sigma$ deviation from the standard model.

Use of upgraded magnet, detector, and storage ring systems.

Abstract

A new measurement of the anomalous magnetic moment of the muon, $a_{\mu} \equiv (g-2)/2$, will be performed at the Fermi National Accelerator Laboratory with data taking beginning in 2017. The most recent measurement, performed at Brookhaven National Laboratory (BNL) and completed in 2001, shows a 3.5 standard deviation discrepancy with the standard model value of $a_\mu$. The new measurement will accumulate 21 times the BNL statistics using upgraded magnet, detector, and storage ring systems, enabling a measurement of $a_\mu$ to 140 ppb, a factor of 4 improvement in the uncertainty the previous measurement. This improvement in precision, combined with recent improvements in our understanding of the QCD contributions to the muon $g$-$2$, could provide a discrepancy from the standard model greater than 7$\sigma$ if the central value is the same as that measured by the BNL experiment, which would be a clear indication of new physics.