Saturation and geometrical scaling: from small x DIS to high energy heavy ion collisions

Abstract

Gluon distributions of colliding hadrons saturate as a result of the non-linear evolution equations of QCD. As a consequence there exists the so called saturation momentum, which is related to the gluon density per unit rapidity per transverse area. When saturation momentum is the only scale for physical processes, dierent observables exhibit geometrical scaling (GS). We show a number of examples of GS and its violation in different reactions.