An Enquiry Concerning Charmless Semileptonic Decays of Bottom Mesons

Abstract

The branching fractions for the decays B → Pℓvℓ, where P are the pseudoscalar charmless mesons π±, π0, η and η' and ℓ is an electron or muon, are measured with B0 and B± mesons found in the recoil of a second B meson decaying as B → Dℓvℓ or B → D*ℓvℓ. The measurements are based on a data set of 348 fb-1 of e+e- collisions at √s = 10.58 GeV recorded with the BABAR detector. Assuming isospin symmetry, measured pionic branching fractions are combined into β(B0 → π-ℓ+vℓ) = (1.54 ± 0.17(stat) ± 0.09(syst)) x 10-4. First evidence of the B+ → ηℓ+vℓ decay is seen; its branching fraction is measured to be β(B+ →ηℓ+vℓ) = (0.64 ± 0.20(stat) ± 0.03(syst)) x 10-4. It is determined that β(B+ → η'ℓ+vℓ) < 0.47 x 10-4 to 90% confidence. Partial branching fractions for the pionic decays in ranges of the momentum transfer and various published calculations of the B → π hadronic form factor are used to obtain values of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element Vub between 3.61 and 4.07 x 10-3.