Improved determination of |Vub| from inclusive semileptonic B-meson decays

Abstract We reduce the perturbative uncertainty in the determination of |Vub| from inclusive semileptonic B decays by calculating the rate of B→X u lν events with dilepton invariant mass q 2 >M B −M D at subleading order in the hybrid expansion, and to next-to-leading order in renormalization-group improved perturbation theory. We also resum logarithmic corrections to the leading power-suppressed contributions. Studying the effect of different b-quark mass definitions we find that the branching ratio after the cut is Br (B→X u lν)=(20.9±4.0)|V ub | 2 , where the dominant error is due to the uncertainty in the b-quark mass. This implies that |Vub| can be determined with a precision of about 10%.