Semileptonic decays of Bc meson to P -wave charmonium states

Zhou Rui, Jie Zhang, Li-li Zhang
2018 Physical Review D  
Inspired by a series of unexpected measurements of semileptonic decays mediated via b→ c charged current interactions, we explore semileptonic B_c decays to the four lightest P-wave charmonium states, χ_c0, χ_c1, χ_c2, h_c, by the recently developed improved perturbative QCD formalism, in which the charm quark mass effect is included both in the Sudakov factor and the hard kernels. We first directly evaluate the concerned transition form factors with vector and axial-vector currents in the
more » ... n of small momentum transfer squared, and then recast them to the full kinematical region by adopting the exponential parametrization. The obtained form factors are used to evaluate the semileptonic decay branching ratios, which can reach the order of 10^-3, letting the corresponding measurement appear feasible. For a better analysis, a comparison of our results with the predictions of other models is provided. We also present the ratios between the tau and light lepton branching ratios and the polarization contributions in the relevant processes, which still need experimental tests in the ongoing and forthcoming experiments. Any significant deviations from the Standard Model results may provide some hints of new physics effects.
doi:10.1103/physrevd.98.033007 fatcat:ni4aecbuw5cetf4lmg7rtrwyfu