Semileptonic decays B c → (η c , J/Ψ)lν in the perturbative QCD approach

In this paper we study the semileptonic decays of Bc⁻ → (ηc,J/ψ)l⁻νₗ. We firstly evaluate the Bc → (ηc,J/Ψ) transition form factors F₀(q²), F₊(q²), V(q²) and A0,1,2(q²) 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 Bc → ηc and Bc → J/Ψ transition form factors agree well with those obtained by using other methods; (b) the pQCD predictions for the branching ratios of the considered decays are Br(Bc⁻ →ηc e⁻νₑ(μ⁻ν_μ)) =(4.41+1.22-1.09)×10⁻³, Br(Bc⁻ →ηcτ⁻ν_τ) =(1.37+0.37-0.34)×10⁻³, Br(Bc⁻ → J/Ψ e⁻νₑ(μ⁻ν_μ)) =(10.03+1.33-1.18)×10⁻³, and Br(Bc⁻ → J/Ψτ⁻ν_τ) =(2.92+0.40-0.34)×10⁻³; and (c) we also define and calculate two ratios of the branching ratios Rηc and RJ/Ψ, which will be tested by LHCb and the forthcoming Super-B experiments.