J/ψ suppression and the quark-gluon plasma

All measured Feynman x(F) distributions of the ratio, R, of J/Psi production in nuclei relative to production on protons fall off with x(F). They show [2] that absorption of charmonium cannot be the only source of J/Psi suppression and that energy loss of the constituents of the incident proton prior to the J/Psi production, because of the exponential root s dependence of the charmonium cross section, should not be neglected. Including the effects of initial state energy loss we find that the latest measured Pb-Pb J/Psi cross sections do not provide any evidence for deconfinement. (C) 1998 Published by Elsevier Science B.V. All rights reserved.