Measurement of the branching fractions of radiative leptonic τ decays , (l=e,μ) at BaBar

We perform a measurement of the branching fractions for , (l=e,μ) decays for a minimum photon energy of 10 MeV in the τ rest frame using 430fb−1 of e+e− collisions collected at the center-of-mass energy of the ϒ(4S) resonance with the BaBar detector at the PEP-II storage rings. We find B(τ→μγνν)=(3.69±0.03±0.10)×10−3 and B(τ→eγνν)=(1.847±0.015±0.052)×10−2 where the first quoted error is statistical and the second is systematic. These results represent a substantial improvement with respect to existing measurements for both channels.