Baryon stopping and valence quark distribution at small x

We argue that the amount of baryon stopping observed in the central rapidity region of heavy-ion collisions at RHIC is proportional to the nuclear valence quark distributions at small x. By generalizing Mueller's dipole model to describe reggeons we construct a non-linear evolution equation for the valence quark distributions at small x in the leading double-logarithmic approximation. The equation includes the effects of gluon saturation in it. The solution of the evolution equation gives a valence quark distribution function dn_val/dy∼e ^-(0.4÷0.5)y. We show that this y-dependence as well as the predictions of regge theory are consistent with the net-proton rapidity distribution reported by BRAHMS.