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Leading particle effect in the J/<FONT FACE=Symbol>y</font> elasticity distribution

Recent DESY-HERA data on J/<FONT FACE="Symbol">Y</font> elasticity distribution show that it emerges mostly as a fast particle. Interpreting photoproduction as a collision between a pre-formed charmed hadron and the proton, the outcoming J/<FONT FACE="Symbol">Y</font> is a leading particle of the collision. We analyse these data using a model formulated to describe energy flow in hadron-hadron reactions. The measured J/<FONT FACE="Symbol">Y</font> spectrum can be successfully described in terms of this model. We conclude that the observed transparency of the charmed hadron-proton collisions arises because of the particularly small gluonic content of the initial c - <img src="http:/img/fbpe/bjp/v28n4/image200.gif" alt="Image200.gif (847 bytes)" align="absbottom"> state.


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