Precision Muon Physics

TL;DR

This paper reviews high-precision muon experiments that probe fundamental physics, including weak interactions, lepton flavor violation, and atomic properties, highlighting novel methods and broad scientific implications.

Contribution

It provides a comprehensive overview of recent and planned muon experiments, emphasizing innovative techniques and their impact on multiple physics domains.

Findings

Muon decay studies confirm weak interaction structure.

Muon magnetic moment measurements test the Standard Model.

Spectroscopy yields precise fundamental constants.

Abstract

The muon is playing a unique role in sub-atomic physics. Studies of muon decay both determine the overall strength and establish the chiral structure of weak interactions, as well as setting extraordinary limits on charged-lepton-flavor-violating processes. Measurements of the muon's anomalous magnetic moment offer singular sensitivity to the completeness of the standard model and the predictions of many speculative theories. Spectroscopy of muonium and muonic atoms gives unmatched determinations of fundamental quantities including the magnetic moment ratio $\mu_\mu / \mu_p$, lepton mass ratio $m_{\mu} / m_e$, and proton charge radius $r_p$. Also, muon capture experiments are exploring elusive features of weak interactions involving nucleons and nuclei. We will review the experimental landscape of contemporary high-precision and high-sensitivity experiments with muons. One focus is the novel methods and ingenious techniques that achieve such precision and sensitivity in recent, present, and planned experiments. Another focus is the uncommonly broad and topical range of questions in atomic, nuclear and particle physics that such experiments explore.