B_c Decays and Lifetime in QCD Sum Rules

In the framework of three-point QCD sum rules, the form factors for the semileptonic decays of B_c --> B_s(B_s^*) l \nu are calculated with account 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 factors are derived at the recoil momentum close to zero. The nonleptonic decays are studied using the assumption on the factorization. The B_c meson lifetime is estimated by summing up the dominating exclusive modes in the c --> s transition combining the current calculations with the previous analysis of b –> c decays in the sum rules of QCD and NRQCD.