NEXT-TO-LEADING ORDER RADIATIVE-CORRECTIONS TO THE DECAY B-]CCS

We calculate the complete O(alpha(s)) 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 m(c)/m(b) = 0.3 and a strange quark mass of 0.2 GeV, we find that the next-to-leading order (NLO) corrections increase Gamma(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, B-SL. of (12.0+/-1.4)% using pole quark masses and (11.2+/-1.7)% using running MS masses.