The effect of gluon depletion on J/psi suppression in pA and AA collisions

Abstract

The enhanced suppression of $J/\psi$ production at large $x_F$ in $pA$ collisions is studied in the framework of gluon depletion at large $x_1$. The nonperturbative process that modifies the gluon distribution as the gluons propagate in nuclear matter is described by an evolution equation with a kernal to be determined by phenomenology. With nuclear shadowing and anti-shadowing taken into account, the effect on the gluon distribution is shown to be a depletion in excess of 40% at $x_1 \approx 0.8$ for $A > 100$. There is a small amount of enhancement of the gluon distribution at small $x_1$, but it does not lead to any contradiction with the existing data on $J/\psi$ suppression in the central region. Extentions to $\psi^{\prime}$ suppression and $AB$ collisions are also investigated in the framework of gluon redistribution.