The Decoupling Problem at RHIC

Abstract

We investigate whether it is possible to dynamically generate from classical transport theory the observed surprising Rout ~ Rside in Au+Au at s^1/2 = 130A GeV at RHIC. We obtained covariant solutions to the Boltzmann transport equation via the MPC technique, for a wide range of partonic initial conditions and opacities. We demonstrate that there exist transport solutions that yield a freezeout distribution with Rout < Rside for Kperp > ~ 1.5 GeV. These solutions correspond to continuous evaporation-like freezeout, where the emission duration is comparable to the source size. Naively this would mean Rout > Rside. Nevertheless, our sources exhibit Rout < Rside because they are narrower in the 'out' than in the 'side' direction and, in addition, a positive x_out-t correlation develops reducing Rout further.