Search for Lepton-Flavor and Lepton-Number Violation in the Decay tau->lhh

TL;DR

This study searches for rare tau decays indicating lepton-flavor and lepton-number violation, using extensive data, and sets upper limits on their occurrence, thus constraining new physics models.

Contribution

First comprehensive search for lepton-flavor and lepton-number violation in tau decays into one lepton and two hadrons with new upper limit constraints.

Findings

No significant excess over background observed.

Upper limits on branching fractions range from 0.7 to 4.8 x 10^{-7}.

Results improve constraints on new physics models.

Abstract

A search for lepton-flavor and lepton-number violation in the decay of the tau lepton into one charged lepton and two charged hadrons is performed using 221.4 $\mathrm{fb}^{-1}$ of data collected at an $e^+e^-$ center-of-mass energy of 10.58 GeV with the BaBar detector at the PEP-II storage ring. In all 14 decay modes considered, the observed data are compatible with background expectations, and upper limits are set in the range ${\cal B}(\tau\to\ell hh')<(0.7-4.8)\times 10^{-7}$ at 90% confidence level.