The Cronin effect, quantum evolution and the color glass condensate

We show that the numerical solution of the classical SU(3) Yang-Mills equations. of motion in the McLerran-Venugopalan model for gluon production in central heavy ion collisions leads to a suppression at low p(t) and an enhancement at the intermediate p(t) region as compared to peripheral heavy ion and pp collisions at the same energy. Our results are compared to previous, color glass condensate inspired calculations of gluon production in heavy ion collisions. We revisit the predictions of the color glass condensate model for pA (dA) collisions in leading order and show that quantum evolution-in particular, the phenomenon of geometric scaling and change of anomalous dimensions-preserves the Cronin enhancement of pA cross section (when normalized to the leading twist term) in the leading order approximation even though the p(t) spectrum can change. We comment on the case when gluon radiation is included. (C) 2003 Published by Elsevier B.V.