Diffusion and local deconfinement in relativistic systems

Abstract

In relativistic systems at RHIC energies, new deconfinement signatures emerge and indicate an increasingly clear separation between soft hadronic processes, and hard partonic interactions in a locally deconfined subsystem. Here the emphasis is on longitudinal variables, namely, net-baryon rapidity distributions. As described in a Relativistic Diffusion Model, they change from bell-shaped at the lower to double-humped at the higher SPS-energy, but do not reach local statistical equilibrium. At sqrt(sNN) = 200 GeV in the Au-Au system, however, they are shown to consist of three components. In addition to the nonequilibrium contributions, a third fraction close to midrapidity containing Z_eq = 22 protons reaches local statistical equilibrium in a discontinuous transition. It may be associated with a deconfinement of the participant partons and thus, serve as a signature for Quark-Gluon Matter formation.