Final state J/ψ suppression in nuclear collisions

The hadron production of J/ψ, ψ’, and Υ on nuclear targets shows two ‘‘initial state’’ effects: a modification of the structure functions in nuclei leads a reduced production relative to p−p interactions, and parton scattering in nuclear matter broadens the transverse momentum spectrum in comparison to that in p−p collisions. If charmonium or bottonium states are to be used as probes for the nature of dense matter formed in nucleus‐nucleus collisions, both these effects must first be taken into account. We do this and discuss the resulting final state features of J/ψ and ψ’ production in high energy heavy ion experiments.