1. Elliptic Flow at RHIC2. Results from CERES/NA45 on flow at 40 AGEV3. Anisotropic Transverse Flow and the Quark Hadron Phase Transition

by (CERN)

Tuesday 24 Oct 2000, 14:00 → 16:30 Europe/Zurich

503/1-001 - Council Chamber (CERN)

1. Elliptic Flow at RHIC by Art Poskanzer (LBNL) Elliptic flow is one of the hadronic observable sensitive to the very early stages of the evolution of the system created in nuclear collisions. We report first results on elliptic flow of charged particles at midrapidity in Au+Au collisions at sqrt(s) = 130 A GeV using the STAR TPC at RHIC. 2. Results from CERES/NA45 on flow at 40 AGEV by TBA Preliminary results on directed and elliptic flow of charged particles from 40 A GeV/c Pb + Au collisions will be reported. 3. Anisotropic Transverse Flow and the Quark Hadron Phase Transition by Peter Kolb (Univ. of Regensburg) The evolution of the fireball matter in the transverse plane of a heavy ion collision is of particular interest, as it exhibits features of flow which can only be explained in terms of large pressure that is built up at early times in the reaction. Elliptic flow, generated in noncentral collisions and resulting in an 'ellipticity' of the particle spectra is sensitive to even earlier stages of the evolution than radial flow. We demonstrate these ideas within a 3+1 dimensional hydrodynamical simulation with boost-invariance in longitudinal direction. We discuss the influence of collision centrality and initial energy density on the transverse flow pattern and the resulting angular distributions of emitted particles near midrapidity for collision energies ranging from AGS to LHC. In this context we examine the influence of a possible phase transition to colour deconfined quark-gluon plasma which could lead to an observable nonmonotonic excitation function of elliptic flow. Comparing our results to the first available data from Au+Au collisions at STAR we conclude that the concepts of early thermalization and hydrodynamics are well applicable in a rather wide range of impact parameters. For large impact parameters however, thermalization seems to be incomplete.

Organiser(s): Yiota Foka, Ulrich Heinz and Urs Wiedemann