An improved perturbative QCD study of the decays Bc^+ ηc L^+

We perform an improved perturbative QCD study of the decays Bc^+ ηc L^+ (L denotes the light ground state pseudoscalar, vector mesons and the corresponding p-wave scalar, axial-vector, and tensor ones) and predict their branching ratios (BRs) associated with relative ratios at leading order in the strong coupling αₛ. Our results BR (Bc^+ ηc π^+) = (2. 03^+0. 53-₀. ₄₁) 10^-3 and BR (Bc^+ ηc π^+) / BR (Bc^+ J/ψπ^+) = 1. 74^+0. 66-₀. ₅₀ are consistent with several available predictions in different approaches within uncertainties. Inputting the measured ηc p p and ηc π^+π^- (π^+π^-, K^+ K^-, p p) BRs with p here being a proton, we derive the multibody Bc^+ ηc (π, ρ) ^+ BRs through secondary decay chains via resonance ηc under the narrow-width approximation, which might facilitate the (near) future tests of Bc ηc decays. Under the q q assignment of light scalars, different to Bc decaying into J/ψ plus a scalar meson and other Bc^+ ηc L^+ modes, surprisingly small BRs around O (10^-7-10^-9) of ΔS =0 modes and highly large ratios near O (10^2) between the BRs of ΔS=1 and ΔS=0 modes are found in the Bc decays to ηc plus light scalars. Many large BRs and interesting ratios presented in this work could be tested at the LHC experiments, which would help us to examine the reliability of this improved perturbative QCD formalism for Bc-meson decays and further understand the QCD dynamics in the considered decay modes, as well as in the related hadrons.