  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
occurs in the Bethe-Heitler regime and the density of gluons and therefore the
suppression goes like $(AB)^{1\over3}$, where $A$ and $B$ are the nucleon
numbers of the projectile and target nuclei. In contrast, the suppression via
collisions with nucleons is proportional to $(A^{1\over3} + B^{1\over3})$.
Parameter free perturbative QCD calculations are in a good agreement with the
data on $J/\Psi$ and $\Psi'$ 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 vanish.
