Search for the Baryon and Lepton Number Violating Decays tau -> Lambda h

TL;DR

This study searched for baryon and lepton number violating tau decays using BABAR data but found no evidence, setting upper limits on their branching fractions to constrain new physics models.

Contribution

First search for specific B and L violating tau decays with the BABAR detector, establishing upper limits on their branching fractions.

Findings

No signal observed for the decay modes.

Upper limits on branching fractions range from 5.8 to 15 x 10^-8.

Results constrain theories predicting baryon and lepton number violation.

Abstract

We have searched for the violation of baryon number B and lepton number L in the (B-L)-conserving modes tau- -> anti-Lambda0 pi- and tau- -> anti-Lambda0 K- as well as the (B-L)-violating modes tau- -> Lambda0 pi- and tau- -> Lambda0 K- using 237 inv. fb of data collected with the BABAR detector at the PEP-II asymmetric-energy e+e- storage ring. We do not observe any signal and determine preliminary upper limits on the branching fractions B(tau- -> anti-Lambda0 pi-) < 5.9 x 10^-8, B(tau- -> Lambda0 pi-) < 5.8 x 10^-8, B(tau- -> anti-Lambda0 K-) < 7.2 x 10^-8, and B(tau- -> Lambda0 K-) < 15 x 10^-8 at 90% confidence level.