Dynamics and Phenomenology of Charmonium Production off Nuclei

Abstract

Nuclear suppression of charmonium production in proton-nucleus interactions is poorly understood, what restrains our attempts to single out unusual effects in heavy ion collisions. We develop a phenomenological approach, based on the light-cone dynamics of charmonium production, which has much in common with deep-inelastic scattering and Drell-Yan lepton pair production. The key observation is the existence of a soft mechanism of heavy flavour production, which scales in the quark mass and dominates shadowing corrections and diffraction. It naturally explains the surprisingly strong nuclear suppression of J/Psi at large Feynman-x_F. The low-x_F region is subject to a complicated interplay of hard and soft mechanisms. With evaluated parameters we nicely describe available data on charmonium production in proton-nucleus collisions. Using these results we predict a new process, diffractive production of charmonium on a nucleon target, which fraction in the total production rate of charmonium is evaluated at 12%.