B-c decays and lifetime in QCD sum rules

In the framework of three-point QCD sum rules, the form factors for the sem ileptonic decays of B-c(+) --> B-s(B-s*)l(+)v(l) are calculated with accoun t for the Coulomb-like alpha(s)/v-corrections in the heavy quarkonium. The generalized relations due to the spin symmetry of HQET/NRQCD for the form f actors are derived at the recoil momentum close to zero. The nonleptonic de cays are studied using the assumption on the factorization. The B-c-meson l ifetime is estimated by summing up the dominating exclusive modes in the c --> s transition combining the current calculations with the previous analy sis of b --> c decays in the sum rules of QCD and NRQCD. (C) 2000 Elsevier Science B.V. All rights reserved.