1212.5903 (Wen-Fei Wang et al.)

Semileptonic decays $B_c\to(η_c,J/Ψ)lν$ in the perturbative QCD
approach    [PDF]

Wen-Fei Wang, Ying-Ying Fan, Zhen-Jun Xiao

In this paper we study the semileptonic decays of $B_c^- \to (\eta_c,J/\psi)l^-\bar\nu_l$ (here $l$ stands for $e, \mu$ and $\tau$). We firstly evaluate the $B_c \to (\eta_c,J/\Psi)$ transition form factors $F_0(q^2)$, $F_+(q^2)$, $V(q^2)$ and $A_{0,1,2}(q^2)$ by employing the pQCD factorization approach, and then we calculate the branching ratios for all considered semileptonic decays. Based on the numerical results and the phenomenological analysis, we find that: (a) the pQCD predictions for the values of the $B_c \to \eta_c$ and $B_c \to J/\Psi$ transition form factors agree with those obtained by using other methods; (b) the pQCD predictions for the branching ratios for the considered modes are $Br(B_c^- \to\eta_c e^-\bar\nu_e(\mu^-\bar\nu_\mu)) =(4.34^{+1.18}_{-1.05})\times10^{-3}$, $Br(B_c^- \to\eta_c\tau^-\bar\nu_\tau) =(1.44^{+0.39}_{-0.35})\times10^{-3}$, $Br(B_c^- \to J/\Psi e^-\bar\nu_e(\mu^-\bar\nu_\mu)) =(8.56^{+1.07}_{-0.98})\times10^{-3}$, and $Br(B_c^- \to J/\Psi\tau^-\bar\nu_\tau) =(2.47^{+0.31}_{-0.28})\times10^{-3}$; and (c) we also define and calculate two ratios of the branching ratios $R_{\eta_c}$ and $R_{J/\Psi}$, which will be tested by LHCb and the forthcoming Super-B experiments.

View original: http://arxiv.org/abs/1212.5903