Near-threshold photoproduction of $$J/\psi $$ J / ψ in two-gluon exchange model

Abstract

Abstract The near-threshold photoproduction of $$J/\psi $$ J / ψ is regarded as one golden process to unveil the nucleon mass structure, pentaquark state involving the charm quarks, and the poorly constrained gluon distribution of the nucleon at large x ( $$>0.1$$ > 0.1 ). In this paper, we present an analysis of the current experimental data under a two-gluon exchange model, which shows a good consistency. Using a parameterized function form with three free parameters, we have determined the nucleonic gluon distribution at the $$J/\psi $$ J / ψ mass scale. Moreover, we predict the differential cross-section of the electroproduction of $$J/\psi $$ J / ψ as a function of the invariant mass of the final hadrons W, at EicC, as a practical application of the model and the obtained gluon distribution. According to our estimation, hundreds of $$J/\psi $$ J / ψ events can be detected per year on EicC near the threshold. Therefore, the relevant experimental measurements are suggested to be carried out on EicC.