Measured Lepton Magnetic Moments

TL;DR

This paper reviews the significance of electron and muon magnetic moments in testing the Standard Model, highlighting their precise measurements, implications for fundamental physics, and the potential for discovering new physics beyond current theories.

Contribution

It provides a comprehensive overview of the current status, experimental techniques, and theoretical implications of lepton magnetic moment measurements in particle physics.

Findings

Electron magnetic moment is the most precisely measured property of an elementary particle.

Muon magnetic moment offers sensitivity to physics beyond the Standard Model.

Advances in measurement and theory have driven progress in quantum field theory and lattice calculations.

Abstract

The electron and muon magnetic moments have played, and continue to play, important roles in testing the fundamental mathematical description of physical reality called the Standard Model of particle physics (SM). The electron magnetic moment is the most precisely measured property of an elementary particle and the most precise SM prediction, setting up the most precise confrontation ever between experiment and theory. It enables the most precise test of quantum field theory, and of the fundamental CPT symmetry invariance of the SM with leptons. The stable electron is studied with quantum methods while the electron remains for months in its quantum ground and first excited states. The muon magnetic moment is one of the most precisely measured property of an unstable elementary particle. Although less precise measured than the electron, it provides greater sensitivity to physics beyond the Standard Model -- a powerful tool for testing the existence of new particles and forces. Because muons decay quickly, they must be studied as they orbit at nearly the speed of light in a large storage ring. The extremely high precision of the electron and muon magnetic moment measurements has driven major advances in theoretical physics, inspiring new techniques in quantum field theory, precision calculations, and lattice gauge theory. Only experimental limits currently exist on the size of the magnetic moments of the tau and neutrino leptons.