Charmonium Suppression - Interplay of Hadronic and Partonic Degrees of Freedom

Abstract

Last year the E866-group of the Fermilab measured the $x_F$ dependence of $J/\Psi$ and ${\Psi }^{\prime }$ suppression in $pA$ collisions. We discuss two of the effects found in that experiment with regard to color coherence effects: the different suppression of the $J/\Psi$ and the ${\Psi }^{\prime }$ at $x_F<0$ and the significant suppression of both at large $x_F$. The small $x_F$ regions is dominated by fully formed charmonium states and thus enables us to discuss the formation time and the cross section of the different charmonium states. In the large $x_F$ region the interaction of the charmonium states with nuclear matter has to be described by partonic degrees of freedom, because in that kinematic domain the formation time is much larger than the nuclear radii. The understanding of this region will be crucial for the interpretation of the data of the future heavy ion colliders RHIC and LHC.

4 pages, 1 table, 1 figure, Contribution to the Proceedings of the 15th Particles and Nuclei International Conference (PANIC 99), Uppsala, Sweden, June 10-16, 1999

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• $J/\psi$ Gluonic Dissociation Revisited : I. Fugacity, Flux And Formation Time Effects
• Charm production in antiproton-nucleus collisions at the $J/\psi$ and the ${\psi }^{\prime }$ thresholds
• Charmonium production in relativistic proton-nucleus collisions : What will we learn from the negative x_F region ?
• Color Screening and the Suppression of the Charmonium State Yield in Nuclear Reactions
• Charmonium dynamics in heavy ion collisions
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