Leading particle effect in the J/psi elasticity distribution

Recent DESY-HERA data on J/Psi elasticity distribution show that it merges mostly as a fast particle. Interpreting photoproduction as a collision betw een a pre-formed charmed hadron and the proton, the outcoming J/Psi is a le ading particle of the collision. We analyse these data using a model formul ated to describe energy flow in hadron-hadron reactions. The measured J/Psi spectrum call be successfully described in terms of this model. We conclud e that the observed transparency of the charmed hadron-proton collisions ar ises because of the particularly small gluonic content of the initial c - ( c) over bar state.