We suggest to study the $B_{ s}$ and its excitations $B_{ sJ}$ in the $B_c$ decays. We calculate the $B_c\to B_{ sJ}$ and $B_c\to B_{ J}$ form factors within the covariant light-front quark model, where the $B_{ sJ}$ and $B_{ J}$ denote an s-wave or p-wave $\bar bs$ and $\bar bd$ meson, respectively. The form factors at $q^2=0$ are directly computed while their $q^2$-distributions are obtained by the extrapolation. The derived form factors are then used to study semileptonic $B_c\to (B_{ sJ},B_{ J})\bar\ell\nu$ decays, and nonleptonic $B_c\to B_{ sJ}\pi$. Branching fractions and polarizations are predicted in the standard model. We find that the branching fractions are sizable and might be accessible at the LHC experiment and future high-energy $e^+e^-$ colliders with a high luminosity at the $Z$-pole. The future experimental measurements are helpful to study the nonperturbative QCD dynamics in the presence of a heavy spectator and also of great value for the spectroscopy study.
Categories: hep-ph