A Model Independent Determination of $|V_{ub}|$

It is shown that measuring the lepton invariant mass spectrum in inclusivesemileptonic 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 aparametrically suppressed role when d\Gamma/dq^2 is integrated over q^2 >(m_B-m_D)^2, which is required to eliminate the charm background. Perturbativeand nonperturbative corrections are presented to order \alpha_s^2\beta_0 and\Lambda_{QCD}^2/m_b^2, and the \Lambda_{QCD}^3/m_b^3 corrections are used toestimate the uncertainty in our results. The utility of the B -> X_s l^+ l^-decay rate above the \psi(2S) resonance is discussed