Cronin effect and high-p_T suppression from the Color Glass Condensate

Abstract

I give a pedagogical survey of the nuclear collective effects associated with gluon saturation and their impact on particle production in high-energy proton (or deuteron)-nucleus collisions at RHIC. At central rapidity, the theory predicts a Cronin peak due to independent multiple scattering off the valence quarks in the nucleus. At forward rapidities, the peak flattens out and disappears very fast, because of the correlations induced through quantum evolution in the nuclear gluon distribution at small x. Also, the ratio R_{pA} between the particle yield in proton-nucleus and proton-proton collisions is rapidly suppressed when increasing the rapidity, because of saturation effects which slow down the evolution of the nucleus compared to that of the proton. This behaviour could be responsible for a similar trend observed in the deuteron-nucleus collisions at RHIC.