UC Berkeley

We report a measurement of the branching fraction of the exclusive charmless semileptonic decay B+→ωℓ+ν, where ℓ is either an electron or a muon. We use samples of B+ mesons tagged by a reconstructed charmed semileptonic decay of the other B meson in the event. The measurement is based on a data set of 426.1 fb-1 of e+e- collisions at a center-of-mass energy of 10.58 GeV recorded with the BABAR detector at the PEP-II asymmetric-energy e +e- storage rings. We measure a branching fraction of B(B+→ωℓ+ν)=(1.35±0.21±0. 11)×10-4, where the uncertainties are statistical and systematic, respectively. We also present measurements of the partial branching fractions in three bins of q2, the invariant-mass squared of the lepton-neutrino system, and we compare them to theoretical predictions of the form factors. © 2013 American Physical Society.