Anisotropic transverse flow and the quark-hadron phase transition - art. no. 054909

We use (3+1)-dimensional hydrodynamics with exact longitudinal boost invari ance to study the influence of collision centrality and initial energy dens ity on the transverse Row pattern and the angular distributions of particle s emitted near midrapidity in ultrarelativistic heavy-ion collisions. We co ncentrate on radial flow and the elliptic Row coefficient nu (2) as functio ns of the impact parameter and collision energy. We demonstrate that the fi nally observed elliptic Row is established earlier in the collision than th e observed radial flow and thus probes the equation of state at higher ener gy densities. We point out that a phase transition from hadronic matter to a color-deconfined quark-gluon plasma leads to nonmonotonic behavior in bot h beam energy and impact parameter dependences which, if observed, can be u sed to identify such a phase transition. Our calculations span collision en ergies from the Brookhaven AGS (Alternating Gradient Synchrotron) to beyond the LHC (Large Hadron Collider); the QGP phase transition signature is pre dicted between the lowest available SPS (CERN Super Proton Synchrotron) and the highest RHIC (Brookhaven Relativistic Heavy Ion Collider) energies. To optimize the chances for applicability of hydrodynamics we suggest studyin g the excitation function of flow anisotropies in central uranium-uranium c ollisions in the side-on-side collision geometry.