Improved perturbative QCD formalism for Bc meson decays

We derive the k(T) resummation for doubly heavy-flavored B-c meson decays by including the charm quark mass effect into the known formula for a heavy-light system. The resultant Sudakov factor is employed in the perutrbative QCD study of the golden channel B-c(+) -> J/Psi pi(+) With a reasonable model for the Bc meson distribution amplitude, which maintains approximate on-shell conditions of both the partonic bottom and charm quarks, it is observed that the imaginary piece of the B-c -> J/Psi transition form factor appears to be power suppressed, and the B-c(+) -> J/Psi pi(+) branching ratio is not lower than 10(-3). The above improved perturbative QCD formalism is applicable to Bc meson decays to other charmonia and charmed mesons.