Theoretical update of the semileptonic branching ratio of B mesons

We reconsider the prediction of the semileptonic branching ratio of B mesons, using the recent calculation [E. Bagan et al., Nucl. Phys. B 432 (1994) 3] of the radiative corrections with account for finite quark masses in nonleptonic decays and taking into account 1 mb2 corrections. For the semileptonic branching ratio we obtain Bsl = (11.8 ± 1.6)% using pole quark masses and Bsl = (11.0 ± 1.9) % using running MS quark masses. The uncertainty is dominated by unknown higher order perturbative corrections. We conclude that the present accuracy of the theoretical analysis does not allow to state a significant disagreement with the experimental results. However, our re-analysis of the decay b → ccs yields an increase of (35 ± 11) % due to next-to-leading order corrections including mass dependent terms, which further emphasizes the problem of the average charm quark content of the final states in B decays. © 1995.