The cross section of the process e ++e −→J/ψ+η c within the QCD light-cone sum rules

Abstract

We calculate the cross section of the exclusive process $e^{+} +e^{-}\to J/\psi+\eta_c$ at the leading order approximation within the QCD light-cone sum rules (LCSR) approach. It is found that the form factor $F_{VP}(V=J/\psi,P=\eta_c)$ depends mainly on the behavior of the twist-2 distribution amplitude of the $\eta_c$-meson at the scale of this process. Thus in order to obtain a reliable estimation of the cross section, it is important to have a realistic distribution amplitude of the $\eta_c$ meson, and to deal with the evolution of the distribution amplitude to the effective energy scale of the process. Our results show that one can obtain a compatible prediction with the Belle and BarBar experimental data.