Tau Physics from B Factories

TL;DR

This paper reviews recent tau physics results from BaBar and Belle experiments, highlighting tests of fundamental symmetries, searches for new physics, and measurements relevant to the muon g-2 and CKM matrix.

Contribution

It provides new measurements and analyses of tau properties, lepton-flavour violation searches, and their implications for Standard Model tests and beyond.

Findings

Tau mass and lifetime measurements support lepton universality.

No evidence found for lepton-flavour violation in tau decays.

Results contribute to understanding muon g-2 and CKM matrix elements.

Abstract

Some recent $\tau$-physics results are presented from the BaBar and Belle experiments at the SLAC and KEK B factories, which produce copious numbers of $\tau$-lepton pairs. Measurements of the tau mass and lifetime allow to test lepton universality and CPT invariance, while searches for lepton-flavour violation in tau decays are powerful ways to look for physics beyond the Standard Model. In semihadronic, non-strange tau decays, the vector hadronic final state is particularly important in helping determine the hadronic corrections to the anomalous magnetic moment of the muon, while studies of strange final states are the best available ways to measure the CKM matrix element $V_{\rm us}$ and the mass of the strange quark.