Entropy production in collisions of relativistic heavy ions : a signal for quark-gluon plasma phase transition?

  • Entropy production in the compression stage of heavy ion collisions is discussed within three distinct macroscopic models (i.e. generalized RHTA, geometrical overlap model and three-fluid hydrodynamics). We find that within these models \sim 80% or more of the experimentally observed final-state entropy is created in the early stage. It is thus likely followed by a nearly isentropic expansion. We employ an equation of state with a first-order phase transition. For low net baryon density, the entropy density exhibits a jump at the phase boundary. However, the excitation function of the specific entropy per net baryon, S/A, does not reflect this jump. This is due to the fact that for final states (of the compression) in the mixed phase, the baryon density \rho_B increases with \sqrt{s}, but not the temperature T. Calculations within the three-fluid model show that a large fraction of the entropy is produced by nuclear shockwaves in the projectile and target. With increasing beam energy, this fraction of S/A decreases. At \sqrt{s}=20 AGeV it is on the order of the entropy of the newly produced particles around midrapidity. Hadron ratios are calculated for the entropy values produced initially at beam energies from 2 to 200 AGeV.

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Author:Manuel Reiter, Adrian Bogdan DumitruORCiDGND, Jörg BrachmannGND, Joachim MaruhnORCiDGND, Horst StöckerORCiDGND, Walter GreinerGND
Document Type:Preprint
Date of Publication (online):2005/11/01
Year of first Publication:1998
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2005/11/01
Source:http://www.arxiv.org/abs/nucl-th/9806010, Report-no: UFTP 477/1998, YRHI-98-11 Journal-ref: Nucl.Phys. A643 (1998) 99-112
Institutes:Physik / Physik
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Licence (German):License LogoDeutsches Urheberrecht