Hadronic contributions to the muon anomalous moment

TL;DR

This paper reviews the hadronic contributions to the muon anomalous magnetic moment, emphasizing the role of light quarks and providing predictions for the light-by-light scattering effects using data-driven methods.

Contribution

It introduces a reliable calculation approach for next-to-leading order hadronic contributions and extends the methodology to the hadronic four-point function for light-by-light scattering.

Findings

Next-to-leading order contributions can be reliably calculated from $e^+ e^-$ data.

A prediction for the light-by-light contribution is provided.

The approach emphasizes the role of chiral symmetry breaking in hadronic effects.

Abstract

We discuss the hadronic contributions to the muon anomalous magnetic moment. They are dominated by light quark contributions which are constrained by the mechanism of chiral symmetry breaking. Using the leading order result based on $e^+ e^-$ scattering data, we show that the next-to-leading order contributions in the fine structure constant $\alpha$ can be reliably calculated. Extending this idea to the hadronic four-point function we give a prediction for the light-by-light contribution.