Determinations of |Vub| from Inclusive Semileptonic B Decays with Reduced Model Dependence

Abstract

We report two novel determinations of | V u b | with reduced model dependence, based on measurements of the mass distribution of the hadronic system in semileptonic B decays. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson from Υ ( 4 S ) → B ¯¯¯ B events. In one approach, we combine the inclusive ¯¯¯ B → X u ℓ ¯ ν rate, integrated up to a maximum hadronic mass m X < 1.67 GeV / c 2 , with a measurement of the inclusive B → X s γ photon energy spectrum. We obtain | V u b | = ( 4.43 ± 0.38 stat ± 0.25 syst ± 0.29 theo ) × 10 − 3 . In another approach we measure the total ¯¯¯ B → X u ℓ ¯ ν rate over the full phase space and find | V u b | = ( 3.84 ± 0.70 stat ± 0.30 syst ± 0.10 theo ) × 10 − 3 .