The $Υ(nS) \to B_{(c)}$ transition form factors and their applications to semileptonic and nonleptonic weak decays

Abstract

The semileptonic and nonleptonic decays of the $Υ(nS)$ with $n=1,2,3,4$ are investigated within the covariant light-front quark model (CLFQM). Using the form factors of the transitions $Υ(nS) \to B_{(c)}$ obtained from the CLFQM, we calculate the branching ratios of the decays $Υ(nS)\to B_{(c)}\ellν_\ell$ and $Υ(nS)\to B_{(c)}M$ with $\ell=e,μ,τ$ and $M$ referring to $π(ρ),K^{(*)},D^{(*)},D^{(*)}_s$. One can find that the branching ratios of the decays $Υ(3S)\to B_c\ellν_\ell$ are the largest among those of considered semileptonic decays and can amount to $10^{-9}$; As to the nonleptonic decays, $Υ(3S)\to B_cρ$ and $Υ(3S)\to B_cD^{(*)}_s$ have the largest branching ratios, which reach up to $10^{-10}$. Given the identification and detection efficiency of final states, searching for these weak decay modes should be fairly challenging in future experiments. The forward-backward asymmetry $A_{FB}$ and the longitudinal polarization fraction $f_L$ are also calculated for those semileptonic decays.