Nonfactorizable contributions in B decays to charmonium: The case of $B^{-}\to K^{-}{h}_c$

Nonleptonic B to charmonium decays generally show deviations from the factorization predictions. For example, the mode $B^{-}\to K^{-}{\chi }_{c0\mathrm{}}$ has been experimentally observed with a sizable branching fraction while its factorized amplitude vanishes. We investigate the role of rescattering effects mediated by intermediate charmed meson production in this class of decay modes, and consider $B^{-}\to K^{-}{h}_c$ with $h_c$ the $J^{\mathrm{PC}}{=1\mathrm{}}^{+-}\overline{c}c$ meson. Using an effective Lagrangian describing interactions of pairs of heavy-light $Q\overline{q}$ mesons with a quarkonium state, we relate this mode to the analogous mode with ${\chi }_{c0\mathrm{}}$ in the final state. We find $\mathcal{B}{(B}^{-}\to K^{-}{h}_c)$ large enough to be measured at B factories, so that this decay mode could be used to study the poorly known $h_c.$