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Review of QGP signatures - ideas versus observables

  • We investigate hadron production and transverse hadron spectra in nucleus-nucleus collisions from 2 A·GeV to 21.3 A·TeV within two independent transport approaches (UrQMD and HSD) based on quark, diquark, string and hadronic degrees of freedom. The enhancement of pion production in central Au+Au (Pb+Pb) collisions relative to scaled pp collisions (the ’kink’) is described well by both approaches without involving a phase transition. However, the maximum in the K+ p+ ratio at 20 to 30 A·GeV (the ’horn’) is missed by ~ 40%. Also, at energies above ~5 A·GeV, the measured K± mT-spectra have a larger inverse slope than expected from the models. Thus the pressure generated by hadronic interactions in the transport models at high energies is too low. This finding suggests that the additional pressure - as expected from lattice QCD at finite quark chemical potential and temperature - might be generated by strong interactions in the early pre-hadronic/partonic phase of central heavy-ion collisions. Finally, we discuss the emergence of density perturbations in a first-order phase transition and why they might affect relative hadron multiplicities, collective flow, and hadron mean-free paths at decoupling. A minimum in the collective flow v2 excitation function was discovered experimentally at 40 A·GeV - such a behavior has been predicted long ago as signature for a first order phase transition.

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Metadaten
Author:Elena L. BratkovskayaORCiDGND, Marcus BleicherORCiDGND, Adrian Dumitru, Kerstin Paech, Manuel Reiter, Sven Soff, Horst StöckerORCiDGND, Henning Weber, Marco van Leeuwen, Wolfgang CassingGND
URN:urn:nbn:de:hebis:30-6708
Parent Title (English):Invited talk presented by H. Stöcker at the International Conference of the NATO Advanced Study Institute 'Structure and Dynamics of Elementary Matter', Kemer, Turkey, 22 Sep.-20 Okt. 2003 (references corrected in the new version)
Document Type:Preprint
Language:English
Date of Publication (online):2005/04/13
Year of first Publication:2004
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2005/04/13
Source:ArXiv nucl-th/0401031 Invited talk presented by H. Stöcker at the International Conference of the NATO Advanced Study Institute 'Structure and Dynamics of Elementary Matter', Kemer, Turkey, 22 Sep.-20 Okt. 2003 (references corrected in the new version)
HeBIS-PPN:12874765X
Institutes:Physik / Physik
Wissenschaftliche Zentren und koordinierte Programme / Frankfurt Institute for Advanced Studies (FIAS)
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Licence (German):License LogoDeutsches Urheberrecht