Role of parton shadowing in the comparison of p-A and A-A results on J/ψ suppression at energies available at the CERN Super Proton Synchrotron

The observation of an anomalous J/ψ suppression in nucleus-nucleus collisions is one of the most important results of the Super Proton Synchrotron (SPS) heavy-ion program. An essential ingredient in this result is the determination, obtained by studying p-A collisions, of effects not related with the formation of a deconfined medium. These effects are extrapolated to A-A collisions, determining a reference J/ψ yield that is then compared with the measurements. In this article we investigate the role of parton shadowing on the determination of such a reference, and we calculate its effect for In-In and Pb-Pb collisions as a function of rapidity and centrality.