Do Higher Order Perturbative Corrections Upset |V_{cb}| and |V_{ub}| Determined from Semileptonic Widths?

Abstract

It is shown that large perturbative corrections found previously for semileptonic beauty and charm decays are associated with using inappropriate pole masses. The latter, in the perturbative expansion, suffer from the 1/m_Q infrared renormalon which is absent in the widths, which leads to similar large corrections in m_Q. Pole masses are neither measured directly in experiment. If the widths are related to parameters determined in experiment, the overall impact of the calculated second order corrections becomes strongly suppressed and leads to less than 1\% change in |V_{cb}| and |V_{ub}|. Even in charm decays the perturbative corrections appear to be very moderate in the consistent OPE-compliant treatment. The updated estimate of |V_{cb}| is given, based on recent accurate determination of m_b and \alpha_s(1 GeV). The theoretical accuracy of determination of |V_{ub}| from \Gamma_{sl}(b->u) appears to be good as well.