Flow at the SPS and RHIC as a quark-gluon plasma signature

Radial and elliptic flow in noncentral heavy-ion collisions can constrain t he effective equation of state (EOS) of the excited nuclear matter To this end, a model combining relativistic hydrodynamics and a hadronic transport code [Sorge, Phys. Rev. C 52, 3291 (1995)] is developed. For an EOS with a first-order phase transition, the model reproduces both the radial and elli ptic Bow data at the SPS. With the EOS fixed from SPS data, we quantify pre dictions at RHIC where the quark-gluon plasma (QCP) pressure is expected to drive additional radial and elliptic flows. Currently, the strong elliptic flow observed in the first RHIC measurements does not conclusively signal this nascent QGP pressure.