Baryon stopping and valence quark distribution at small x [Review]

摘要

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 similar to e(-(0.4divided by0.5)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. (C) 2003 Elsevier B.V. All rights reserved. [References: 116]