New results on nuclear dependence of J/psi and psi production in 450 GeV pA collisions

To understand the reliability of the charmonia suppression as a signature of the Quark-Gluon Plasma formation in nucleus-nucleus collisions it is important first to understand the details of the production of J/psi and psi in pA interactions and the difference in the suppression of these two states. This report presents the results of the study by the NA50 collaboration of the J/psi and psi production in pA interactions at 450 GeV beam energy and its dependence on rapidity. It is shown that the psi suffers more suppression than the J/psi, which is consistent with a similar observation made at 800 GeV beam energy by the E866/NuSea collaboration.