Semileptonic Decays Of B_c Meson To P-wave Charmonium States

Recently,a number of experimental measurements have shown interesting deviations from their Standard Model?SM?expectations in several b?c charged current decay proceses.Based on the improved PQCD method,the semileptonic decay of Bc meson to the four lightest p-wave charmonium,such as:?_c0??_c1??_c2?h_c,are studied,in which the charm quark mass effect is involved.The weak decay process contains both perturbative and non-perturbative contributions,in which the former is process dependence and can be calculated based on the perturbative expansion,while the latter contains a long range contribution and incalculable.According to the universality of hadron wave function,it can be determined by QCDSR or LFQM.Since the charm quark is heavy,the traditional perturbation QCD method does not consider the charm quark mass in Sudakov factor.In order to improve the theoretical calculation accuracy,the charm quark mass effect is included both in Sudakov factor and hard scattering kernel.Based on the QCD Feynman rules,by using the Mathematica,Fortran and the package of the High-Energy-Physics,concerned transition form factors with vector and axial-vector currents in the region of small momentum transfer squared are evaluated first.Then,it is recasted 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.The ratios between the tau and light lepton branching ratios and the polarization contributions in the relevant processes are also present.A future improvable measurement might reveal whether a similar anomaly exists in these ratios.Any significant deviations from the Standard Model results may provide some hints of new physics effects.Figure 10;Table 6;Reference 62...