Anisotropy of flow and the order of phase transition in relativistic heavy ion collisions

Using a hydrodynamical model we study how the order of phase transition in the equation of state of strongly interacting matter affects single particle spectra, elliptic flow and higher order anisotropies in An + An collisions at RHIC (root(NN)-N-s = 200 GeV energy). We find that the single particle spectra are independent of the order of phase transition and that the fourth harmonic nu(4)(PT) shows only a weak dependence in the PT region where hydrodynamics is expected to work. The differential elliptic flow, nu(2)(PT), of baryons shows the strongest dependence on equation of state. Surprisingly the closest fit to data was obtained when the equation of state had a strong first order phase transition and a lattice inspired equation of state fits the data as badly as a purely hadronic equation of state. (c) 2005 Elsevier B.V. All rights reserved.