Search for Lepton Flavor Violation in Upsilon Decays

TL;DR

This paper reports a search for lepton flavor violation in Upsilon meson decays, setting upper limits on such processes and interpreting the results within an effective field theory framework.

Contribution

First search for LFV in Upsilon decays using CLEO III data, establishing upper limits and constraining new physics models.

Findings

95% CL upper limits on LFV branching fractions

Constraints on new interaction energy scales and couplings

No evidence of LFV observed in Upsilon decays

Abstract

In this Letter we describe a search for lepton flavor violation (LFV) in the bottomonium system. We search for leptonic decays of Upsilon(nS)(n=1,2, and 3) into muon and tau using the data collected with the CLEO III detector. We identify the tau lepton using its leptonic decay into electron and utilize multidimensional likelihood fitting with PDF shapes measured from independent data samples. We report our estimates of 95% CL upper limits on LFV branching fractions of Upsilon mesons. We interpret our results in terms of the exclusion plot for the energy scale of a hypothetical new interaction versus its effective LFV coupling in the framework of effective field theory.