Cold nuclear matter effects on J / ψ production: Intrinsic and extrinsic transverse momentum effects

Cold nuclear matter effects on J / ψ production in proton-nucleus and nucleus-nucleus collisions are evaluated taking into account the specific J / ψ-production kinematics at the partonic level, the shadowing of the initial parton distributions and the absorption in the nuclear matter. We consider two different parton processes for the c over(c, ̄)-pair production: one with collinear gluons and a recoiling gluon in the final state and the other with initial gluons carrying intrinsic transverse momentum. Our results are compared to RHIC observables. The smaller values of the nuclear modification factor R_{A A} in the forward rapidity region (with respect to the mid rapidity region) are partially explained, therefore potentially reducing the need for recombination effects.