Ideal hydrodynamics and elliptic flow at CERN Super Proton Synchrotron (SPS) energies: Importance of the initial conditions

Journal Article · Fri May 15 00:00:00 EDT 2009 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.79.054904· OSTI ID:21286968

Petersen, Hannah ^[1]; Bleicher, Marcus ^[2]

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1. Frankfurt Institute for Advanced Studies (FIAS), Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main (Germany)
2. Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany)

The elliptic flow excitation function calculated in a full (3+1) dimensional hybrid Boltzmann approach with an intermediate hydrodynamic stage for heavy ion reactions from GSI Schwerionen Synchrotron to the highest CERN Super Proton Synchrotron (SPS) energies is discussed in the context of the experimental data. In this study, we employ a hadron gas equation of state to investigate the differences in the dynamics and viscosity effects. The specific event-by-event setup with initial conditions and freeze-out from a nonequilibrium transport model allows for a direct comparison between ideal fluid dynamics and transport simulations. At higher SPS energies, where the pure transport calculation cannot account for the high elliptic flow values, the smaller mean free path in the hydrodynamic evolution leads to higher elliptic flow values. In contrast to previous studies within pure hydrodynamics, the more realistic initial conditions employed here and the inclusion of a sequential final state hadronic decoupling provides results that are in line with the experimental data almost over the whole energy range from E{sub lab}=2-160A GeV. Thus, this new approach leads to a substantially different shape of the v{sub 2}/{epsilon} scaling curve as a function of (1/SdN{sub ch}/dy) in line with the experimental data compared to previous ideal hydrodynamic calculations. This hints at a strong influence of the initial conditions for the hydrodynamic evolution on the finally observed v{sub 2} values, thus questioning the standard interpretation that the hydrodynamic limit is only reached at BNL Relativistic Heavy Ion Collider energies.

• OSTI ID: 21286968
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 79, Issue 5; Other Information: DOI: 10.1103/PhysRevC.79.054904; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BNL
BROOKHAVEN RHIC
CERN SPS SYNCHROTRON
COMPARATIVE EVALUATIONS
DECOUPLING
EQUATIONS OF STATE
EVOLUTION
EXCITATION FUNCTIONS
FREEZING OUT
GEV RANGE
HEAVY ION REACTIONS
HYDRODYNAMIC MODEL
IDEAL FLOW
MEAN FREE PATH
PROTONS
SIMULATION
THREE-DIMENSIONAL CALCULATIONS
TRANSPORT THEORY
VISCOSITY