Charmonium suppression in heavy ion collisions by prompt gluons

In relativistic heavy ion collisions, also the bremsstrahlung of gluons in the fragmentation regions of the nuclei suppresses the produced charmonium states. In the energy range of the SPS, the radiation of semi-hard gluons o ccurs in the Bethe-Heitler regime and the density of gluons and therefore t he suppression goes like (AB)(1/3), where A and B are the nucleon numbers o f the projectile and target nuclei. In contrast, the suppression via collis ions with nucleons is proportional to (A(1/3) + B-1/3). Parameter free pert urbative QCD calculations are in a good agreement with the data on J/Psi an d Psi' suppression in heavy ion collisions at SPS CERN. At higher energies (RHIC, LHC) the number of gluons which are able to break-up the charmonium substantially decreases and the additional suppression is expected to vanis h. (C) 1998 Elsevier Science B.V. All rights reserved.