Measurement of the branching fractions of the radiative leptonic tau decays tau -> e gamma nu anti-nu and tau -> mu gamma nu anti-nu at BaBar

TL;DR

This paper reports precise measurements of the branching fractions for tau leptonic radiative decays to electrons and muons, using BaBar data, improving upon previous experimental results.

Contribution

The study provides the most accurate measurements to date of tau radiative decay branching fractions for the first time with such precision.

Findings

Measured B(tau -> mu gamma nu anti-nu) = (3.69 ± 0.03 ± 0.10) x 10^-3

Measured B(tau -> e gamma nu anti-nu) = (1.847 ± 0.015 ± 0.052) x 10^-2

Results are significantly more precise than previous measurements.

Abstract

We perform a measurement of the tau -> l gamma nu anti-nu (l = e, mu) branching fractions for a minimum photon energy of 10 MeV in the tau rest frame, using 431fb^-1 of e^+e^- collisions collected at the center-of-mass energy of the Upsilon(4S) resonance with the BaBar detector at the PEP-II storage rings. We find B(tau -> mu gamma nu anti-nu ) = (3.69pm0.03pm0.10)x10^-3, and B(tau -> e gamma nu anti-nu ) = (1.847pm0.015pm0.052)x10^-2, where the first quoted error is statistical, and the second is systematic. These results are substantially more precise than previous measurements.