Next-to-leading order radiative corrections to the decay b → ccs

We calculate the complete O(αs) corrections to the quark decay b → ccs taking full account of the quark masses, but neglecting penguin contributions. For a c to the b quark mass ratio mcmb = 0.3 and a strange quark mass of 0.2 GeV, we find that the next-to-leading order (NLO) corrections increase Γ(b → ccs) by (32 ± 15) % with respect to the leading order expression, where the uncertainty is mostly due to scale- and scheme-dependencies. Combining this result with the known NLO and non-perturbative corrections to other B meson decay channels we obtain an updated value for the semileptonic branching ratio of B mesons, BSL, of (12.0 ± 1.4) % using pole quark masses and (11.2 ± 1.7) % using running MS masses.