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Transport Model Studies of HIC and the Quest for the QGP

Transport Model Studies of HIC and the Quest for the QGP. Marcus Bleicher Institut für Theoretische Physik Goethe Universität Frankfurt Germany. The scales. The Topic: QGP. The Task: Recreate Quark-Hadron Transition in the Laboratory. The tools: Accelerators. SIS (GSI) AGS (BNL)

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Transport Model Studies of HIC and the Quest for the QGP

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  1. Transport Model Studies of HICand the Quest for the QGP Marcus Bleicher Institut für Theoretische Physik Goethe Universität Frankfurt Germany Marcus Bleicher, CSC Seminar Day 2004

  2. The scales Marcus Bleicher, CSC Seminar Day 2004

  3. The Topic: QGP The Task: Recreate Quark-Hadron Transition in the Laboratory Marcus Bleicher, CSC Seminar Day 2004

  4. The tools: Accelerators • SIS (GSI) • AGS (BNL) • SIS-200 (GSI) • SPS (CERN) • RHIC (BNL) • LHC (CERN) Marcus Bleicher, CSC Seminar Day 2004

  5. The results: Tracks Brahms experiment Marcus Bleicher, CSC Seminar Day 2004

  6. AuAu 5% The physics result Does this mean Quark-Gluon-Plasma? Maybe? Ask your favorite theoretician! Marcus Bleicher, CSC Seminar Day 2004

  7. Signatures of a QGP Marcus Bleicher, CSC Seminar Day 2004

  8. Our tool: UrQMD • Non-equilibrium transport model • Hadrons and resonances • String excitation and fragmentation • Cross sections are parametrizedvia AQM or calculated by detailed balance • Generates full space-time dynamics of hadrons and strings Marcus Bleicher, CSC Seminar Day 2004

  9. Our tool: UrQMD Full collision term consists of ~10000 different two particle combinations Marcus Bleicher, CSC Seminar Day 2004

  10. Our tool: UrQMD Includes parametrized and/or calculated energy dependent cross sections Marcus Bleicher, CSC Seminar Day 2004

  11. PP Excitation functions PP works nicely in both models Pythia used for hard scatterings above 50 GeV Marcus Bleicher, CSC Seminar Day 2004

  12. UrQMD event Marcus Bleicher, CSC Seminar Day 2004

  13. UrQMD event Marcus Bleicher, CSC Seminar Day 2004

  14. Strangeness enhancement • q+qbar -> s+sbar (0.3 GeV) • g+g -> s+sbar (0.3 GeV) • pi+pi -> K+Kbar (1.0 GeV) T~0.2-0.3 GeV QGP has lower threshold for strangeness production -> relative strangeness enhancement Marcus Bleicher, CSC Seminar Day 2004

  15. AA Excitation functions • 4 and mid-y abundancies: OK • Energy dependence: OK • Hadron-string models work well Marcus Bleicher, CSC Seminar Day 2004

  16. Excitation functions: ratios • ‘Horn’ in the ratio not reproduced • well reproduced • relative strange baryon enhancement reproduced Marcus Bleicher, CSC Seminar Day 2004

  17. Ratio excitation functions: Summary • Yields are well reproduced • Most ratios can be understood in transport models • Model K/pi ratios do not reproduce the strong peak observed in data Marcus Bleicher, CSC Seminar Day 2004

  18. Latent heat The transition to a QGP is like cooking water. At the phase transition energy is put into the system, but it does not heat up. Marcus Bleicher, CSC Seminar Day 2004

  19. Transverse mass spectra • Standard UrQMD and HSD underestimate the data • Additional resonances from 2-3 GeV may improve the description (UrQMD 2.1) Marcus Bleicher, CSC Seminar Day 2004

  20. Inverse slope systematics • Standard transport models fail • What is missing? • Maybe high mass resonanceslike in UrQMD 2.1 • Maybe Cronin effect at high • energies (HSD) • Maybe initial QGP pressure… Marcus Bleicher, CSC Seminar Day 2004

  21. Flow excitation functions: Summary • Standard transport models can not describe radial flow • Inclusion of high mass resonances leads to additional flow (maybe necessary at low energies) • Inclusion of Cronin effect leads to additional flow (maybe necessary at high energies) • Assumption of an early QGP phase might create additional flow Marcus Bleicher, CSC Seminar Day 2004

  22. Phase diagram • QGP might be reachedalready at low SPS energy ! • Tricritical point around 10-40 GeV • No phase transition at RHIC • Necessary to explore 10-30 AGeV energy region to study the phase transition Marcus Bleicher, CSC Seminar Day 2004

  23. Thanks • Elena Bratkovskaya • Henning Weber • Manuel Reiter • Sascha Vogel • Xianglei Zhu • Horst Stoecker Marcus Bleicher, CSC Seminar Day 2004

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