Test of lepton universality and searches for lepton flavor violation at BaBar

TL;DR

The BaBar experiment conducted comprehensive searches for lepton universality and lepton flavor violation using extensive datasets, setting new limits on various decay processes involving tau and muon leptons.

Contribution

This paper reports new experimental limits on lepton flavor violating decays and tests of lepton universality using the full BaBar dataset, advancing constraints on new physics models.

Findings

New limits on $ au$ decay modes to three leptons

Constraints on lepton flavor violating $S$ and $S$ decays

Results supporting lepton universality in $
S$ decays

Abstract

The BaBar experiment has recently obtained some important results in the search for new physics in leptonic and lepton flavor violating decays, exploiting the complete datasets collected at the $\Upsilon(4S)$, $\Upsilon(3S)$ and $\Upsilon(2S)$ energies. In particular, new limits on the ratio $\Gamma(\Upsilon(1S)\to\tau^+\tau^-)/\Gamma(\Upsilon(1S)\to\mu^+\mu^-)$, on lepton flavor violating decays of the $\Upsilon(3S)$ and $\Upsilon(2S)$, and on $\tau$ decays to three charged leptons or $\tau\to e/\mu \gamma$ are presented.