Inclusive Measure of |Vᵤb| with the Analytic Coupling Model

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By analyzing B -> Xᵤ l nuₗ spectra with a model based on soft-gluon resummation and an analytic time-like QCD coupling, we obtain |Vᵤb| = (3.76 +-0.13 +- 0.22)*10(-3), where the first and the second error refers to experimental and theoretical errors, respectively. The Vᵤb value is obtained from the available measured semileptonic branching fractions in limited regions of the phase-space. The distributions in the lepton energy Eₗ, the hadron invariant mass mₓ, the light-cone momentum P+ = Eₓ - pₓ, together with the double distributions in (mₓ,q²) and (Eₗ,sₕᵐax), are used to select the phase-space regions. The q² is the dilepton squared momentum and sₕᵐax is the maximal mₓ² at fixed q² and Eₗ. The Vᵤb value obtained is in complete agreement with the value coming from exclusive B decays and from an over-all fit to the Standard Model parameters. We show that the slight disagreement (up to +2 sigma) with respect to previous inclusive measurements is not related to different choices for the b (and c) masses but to a different modelling of the threshold (Sudakov) region.