Local thermal and chemical equilibration and the equation of state in relativistic heavy ion collisions

Thermodynamical variables and their time evolution are studied for central relativistic heavy ion collisions from 10.7 to 160 AGeV in the microscopic Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). The UrQMD 
Thermodynamical variables and their time evolution are studied for central relativistic heavy ion collisions from 10.7 to 160 AGeV in the microscopic Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). The UrQMD model exhibits drastic deviations from equilibrium during the early high density phase of the collision. Local thermal and chemical equilibration of the hadronic matter seems to be established only at later stages of the quasi-isentropic expansion in the central reaction cell with volume 125 fm 3. Baryon energy spectra in this cell are reproduced by Boltzmann distributions at all collision energies for t > 10 fm/c with a unique rapidly dropping temperature. At these times the equation of state has a simple form: P = (0.12 - 0.15) Epsilon. At SPS energies the strong deviation from chemical equilibrium is found for mesons, especially for pions, even at the late stage of the reaction. The final enhancement of pions is supported by experimental data.
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Metadaten
Author:Larissa V. Bravina, Mathias Brandstetter, Mark I. Gorenstein, Eugene E. Zabrodin, Mohamed Belkacem, Marcus Bleicher, Steffen A. Bass, Christoph Ernst, M. Hofmann, Sven Soff, Horst Stöcker, Walter Greiner
URN:urn:nbn:de:hebis:30-6900
Document Type:Preprint
Language:English
Date of Publication (online):2005/04/13
Year of first Publication:1998
Publishing Institution:Univ.-Bibliothek Frankfurt am Main
Release Date:2005/04/13
Source:http://de.arxiv.org/abs/nucl-th/9810036 , Talk given at SQM'98 conference, 20-24 July 1998, Padova, Italy, submitted to J. Phys. G
HeBIS PPN:128782323
Institutes:Physik
Dewey Decimal Classification:530 Physik
PACS-Classification:24.10.Lx Monte Carlo simulations (including hadron and parton cascades and string breaking models)
24.10.Pa Thermal and statistical models
Sammlungen:Universitätspublikationen
Licence (German):License Logo Veröffentlichungsvertrag für Publikationen

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