Branching fraction and form-factor shape measurements of exclusive charmless semileptonic B decays, and determination of |[subscript Vub]|

Abstract

We report the results of a study of the exclusive charmless semileptonic decays, B[superscript 0]→π[superscript -]ℓ[superscript +]ν, B[superscript +]→π[superscript 0]ℓ[superscript +]ν, B[superscript +]→ωℓ[superscript +]ν, B[superscript +]→ηℓ[superscript +]ν, and B[superscript +]→η[superscript ′]ℓ[superscript +]ν (ℓ=e or μ) undertaken with approximately 462×106 BB̅ pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q[superscript 2], the square of the momentum transferred to the lepton-neutrino pair, for B[superscript 0]→π[superscript -]ℓ[superscript +]ν, B[superscript +]→π[superscript 0]ℓ[superscript +]ν, B[superscript +]→ωℓ[superscript +]ν, and B[superscript +]→ηℓ[superscript +]ν. From these distributions, we extract the form-factor shapes f+(q[superscript 2]) and the total branching fractions B(B[superscript 0]→π[superscript -]ℓ[superscript +]ν)=(1.45±0.04[subscript stat]±0.06syst)×10[superscript -4] (combined π[superscript -] and π[superscript 0] decay channels assuming isospin symmetry), XXXXXX B(B+→ωℓ+ν)=(1.19±0.16stat±0.09syst)×10-4 and B(B+→ηℓ+ν)=(0.38±0.05stat±0.05syst)×10-4. We also measure B(B+→η′ℓ+ν)=(0.24±0.08stat±0.03syst)×10-4. We obtain values for the magnitude of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |Vub| by direct comparison with three different QCD calculations in restricted q2 ranges of B→πℓ+ν decays. From a simultaneous fit to the experimental data over the full q2 range and the FNAL/MILC lattice QCD predictions, we obtain |Vub|=(3.25±0.31)×10-3, where the error is the combined experimental and theoretical uncertainty.