  Charmonium states are expected to be considerably suppressed in the case of
quark-gluon plasma formation in high-energy heavy-ion collisions. However, a
robust identification of suppression patterns as signatures of a deconfined QCD
medium requires a detailed understanding of the "normal nuclear absorption"
already present in proton-nucleus collisions, where the charmonium production
cross sections increase less than linearly with the number of target nucleons.
We analyse the J/psi production cross sections measured in proton-nucleus
collisions in fixed target experiments, with proton beam energies from 200 to
920 GeV, and in d-Au collisions at RHIC, at sqrt(s)=200 GeV, in the framework
of the Glauber formalism, using several sets of parton distributions with and
without nuclear modifications. The results reveal a significant dependence of
the "absorption cross section" on the kinematics of the J/psi and on the
collision energy. Extrapolating the observed patterns we derive the level of
absorption expected at Elab=158 GeV, the energy at which the heavy-ion data
sets were collected at the CERN SPS.

High Energy Physics - Phenomenology