A Model Independent Determination of |V_{ub}|

Abstract

It is shown that measuring the lepton invariant mass spectrum in inclusive semileptonic B -> X_u l nu decay yields a model independent determination of |V_{ub}|. Unlike the lepton energy and hadronic invariant mass spectra, nonperturbative effects are only important in the resonance region, and play a parametrically suppressed role when dΓ/dq^2 is integrated over q^2 > (m_B-m_D)^2, which is required to eliminate the charm background. Perturbative and nonperturbative corrections are presented to order α_s^2β_0 and Λ_{QCD}^2/m_b^2, and the Λ_{QCD}^3/m_b^3 corrections are used to estimate the uncertainty in our results. The utility of the B -> X_s l^+ l^- decay rate above the ψ(2S) resonance is discussed.