Centrality, Rapidity and Transverse-Momentum Dependence of Cold Nuclear Matter Effects on J/Psi Production in d+Au, Cu+Cu and Au+Au Collisions at sqrt(s_NN)=200 GeV

Abstract

We have carried out a wide study of Cold Nuclear Matter (CNM) effects on J/Psi production in d+Au, Cu+Cu and Au+Au collisions at sqrt(s_NN)=200 GeV. We have studied the effects of three different gluon-shadowing parametrisations, using the usual simplified kinematics for which the momentum of the gluon recoiling against the J/Psi is neglected as well as an exact kinematics for a 2 -> 2 process, namely g+g -> J/psi+g as expected from LO pQCD. We have shown that the rapidity distribution of the nuclear modification factor R_dAu, and particularly its anti-shadowing peak, is systematically shifted toward larger rapidities in the 2 -> 2 kinematics, irrespective of which shadowing parametrisation is used. In turn, we have noted differences in the effective final-state nuclear absorption necessary to fit the PHENIX d+Au data. Taking advantage of our implementation of a 2 -> 2 kinematics, we have also computed the transverse momentum dependence of the latter nuclear modification factor, which cannot be predicted with the usual simplified kinematics. All the corresponding observables have been computed for Cu+Cu and Au+Au collisions and compared to the PHENIX and STAR data. Finally, we have extracted the effective nuclear absorption from the recent measurements of R_CP in d+Au by the PHENIX collaboration.