Improved perturbative QCD formalism for Bc meson decays

Xin Liu, Hsiang-nan Li, Zhen-Jun Xiao 2018 Phys.Rev. D 97.113001 

We derive the kT resummation for doubly heavy-flavored Bc 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” Bc+→J/ψπ+. 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 Bc→J/ψ transition form factor appears to be power suppressed, and the Bc+→J/ψπ+ 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.