Small x parton distributions and initial conditions in ultrarelativistic nuclear collisions

Abstract

At the colliders RHIC and LHC, nuclei at the ultrarelativistic energies of $100$ GeV/A and $2.7$ TeV/A will be smashed together with the hope of creating an elusive and short-lived state of matter called the quark gluon plasma. The initial conditions which determine the dynamical evolution of the quark gluon matter formed in the central region after the collision depend crucially on the small $x$ component of the nuclear wavefunction before the collision. In this comment, we discuss recent work which argues that, for large nuclei, weak coupling techniques in QCD can be used to calculate the distribution of these small $x$, or wee, partons. The ramifications of this approach for the dynamics of heavy ion collisions and the various signatures of a quark gluon phase of matter are discussed.