Leptons and QCD

TL;DR

This paper reviews key QCD aspects related to tau and muon physics, including determining the strong coupling constant, measuring CKM matrix element |V_{us}|, and predicting the muon anomalous magnetic moment within the Standard Model.

Contribution

It provides updated measurements and theoretical predictions for QCD parameters and processes involving tau and muon decays.

Findings

Updated value of alpha_s(m_tau^2) = 0.331 ± 0.013

Measurement of |V_{us}| from tau decays

Standard Model prediction for muon g-2

Abstract

Three important QCD-related aspects of the $\tau$ and $\mu$ dynamics are reviewed: the determination of the strong coupling from the hadronic tau decay width, leading to the updated value $\alpha_s(m_\tau^2) = 0.331 \pm 0.013$; the measurement of $|V_{us}|$ through the Cabibbo-suppressed decays of the $\tau$, and the Standard Model prediction for the muon anomalous magnetic moment.