What the collective flow excitation function can tell about the quark-gluon plasma
Abstract
Recent STAR data from the RHIC beam energy scan (BES) show that the midrapidity slope dv1/dy of the directed flow v1 of net-protons changes sign twice within the collision energy range 7.7 - 39 GeV. To investigate this phenomenon, we study the collision energy dependence of v1 utilizing a Boltzmann + hydrodynamics hybrid model. Calculations with dynamically evolved initial and final state show no qualitative difference between an equation of state with a cross-over and one with a first-order phase transition, in contrast to earlier pure fluid predictions. Furthermore, our analysis of the elliptic flow v2 shows that pre-equilibrium transport dynamics are partially compensating for the diminished elliptic flow production in the hydrodynamical phase at lower energies, which leads to a qualitative agreement with STAR BES results in midcentral collisions. No compensation from transport is found in our model for integrated v3, which decreases from approx 0.02 at sqrt(sNN) = 27 GeV to approx 0.005 at sqrt(sNN) = 7.7 GeV in midcentral collisions.
Keywords
Cite
@article{arxiv.1408.0098,
title = {What the collective flow excitation function can tell about the quark-gluon plasma},
author = {Jussi Auvinen and Jan Steinheimer and Hannah Petersen},
journal= {arXiv preprint arXiv:1408.0098},
year = {2015}
}
Comments
8 pages (preprint format), 2 figures. Talk given at Quark Matter 2014, Darmstadt, Germany, May 19 - 24, 2014