Observeration of Radiative Leptonic Decay of the Tau Lepton

TL;DR

This paper reports the measurement of radiative leptonic decay branching fractions of the tau lepton using CLEO II data, confirming consistency with Standard Model predictions.

Contribution

First precise measurement of tau radiative decay branching fractions with CLEO II data, providing experimental validation of Standard Model predictions.

Findings

Branching fraction for tau to mu gamma: (3.61+-0.16+-0.35)*10^{-3}

Branching fraction for tau to e gamma: (1.75+-0.06+-0.17)*10^{-2}

Results agree with Standard Model predictions

Abstract

Using 4.68 fb^{-1} of e^+e^- annihilation data collected with the CLEO II detector we have studied tau radiative decays tau --> mu nu nu gamma and tau --> e nu nu gamma. For a 10 MeV minimum photon energy in the tau rest frame, the branching fraction of a tau radiatively decaying to a muon is measured to be (3.61+-0.16+-0.35)*10^{-3}, and to an electron is (1.75+-0.06+-0.17)*10^{-2}. The branching fractions are in agreement with the Standard Model theoretical predictions. All quoted results are preliminary.