Saturation and Pion Production in Proton-Nucleus Collisions

We study the effects of gluon saturation on pion production in high energy proton-nucleus collisions using the color glass condensate model. At high p_perp, we show that the p_perp-distribution of gluons behaves as ~ 1/(p_perp^7) in accordance with both conventional perturbative QCD calculations and experiment. Fragmentation of gluons into pions leads to a rapidity dependent depletion of pions relative to the conventional perturbative QCD predictions. We argue that these clear and systematic differences provide a signal for the onset of gluon saturation which is accessible in upcoming experiments.