Bcexclusive decays to charmonium and a light meson at next-to-leading order accuracy

Abstract

In this paper, we study the ${B}_{c}$-meson exclusive decays to S-wave charmonia and light pseudoscalar or vector mesons, i.e., $\ensuremath{\pi}$, $K$, $\ensuremath{\rho}$, and ${K}^{*}$ at the next-to-leading order (NLO) in the QCD coupling. The nonfactorizable contribution is included, which is absent in traditional naive factorization. Numerical results show that NLO QCD corrections markedly enhance the branching ratio with a $K$ factor of 1.75 for ${B}_{c}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and 1.31 for ${B}_{c}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ using certain input parameters. And the theoretical uncertainties for their branching ratios are reduced compared with that of direct tree-level calculation. In order to investigate the asymptotic behavior, the analytic form is obtained in the heavy quark limit, i.e., ${m}_{b}\ensuremath{\rightarrow}\ensuremath{\infty}$. We note that annihilation topologies contribute trivia in this limit, and the corrections at leading order in $z={m}_{c}/{m}_{b}$ expansion come from form factors and hard spectator interactions. At last, some related phenomenologies are also discussed.