Double scattering effect in the transverse momentum distribution of inclusive J/ψ production in photo-nucleus collisions Original Research Article

In terms of multiple scattering picture, we calculate the double scattering effect in the transverse momentum distribution of J/ψ photoproduction. Applying the generalized factorization theorem, we find that the contributions from double scattering can be expressed in terms of twist-4 nuclear parton correlation functions, which is the same as that used to explain the nuclear dependence in di-jet momentum imbalance and in direct photon production. Using known information on the twist-4 parton correlation functions, we estimate that the double scattering contributes a small suppression in J/ψ photoproduction. In the analysis we only take into account the leading order in the small velocity expansion for the non-perturbative parts related to the quarkonium.