Yang-Mills radiation in ultrarelativistic nuclear collisions

Abstract

The classical Yang-Mills radiation computed in the McLerran-Venugopalan model is shown to be equivalent to the gluon bremsstrahlung distribution to lowest ${(g}^{6})$ order in pQCD. The classical distribution is also shown to match smoothly onto the conventional pQCD minijet distribution at a scale ${k}_{\ensuremath{\perp}}^{2}\ensuremath{\sim}\ensuremath{\chi}$, characteristic of the initial parton transverse density of the system. The atomic number and energy dependence of $\ensuremath{\chi}$ is computed from available structure function information. The limits of applicability of the classical Yang-Mills description of nuclear collisions at RHIC and LHC energies are discussed.