Improved Determination of |Vub| from Inclusive Semileptonic B-Meson Decays

We reduce the perturbative uncertainty in the determination of |Vub| from inclusive semileptonic B decays by calculating the rate of B → Xu l ν events with dilepton invariant mass √ q2 > MB −MD 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 → Xu l ν) = (20.9 ± 4.0) |Vub|, 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%.