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Space time evolution of QCD matter

Johann Wolfgang Goethe-Universität Frankfurt Institut für Theoretische Physik. Space time evolution of QCD matter. I. Bouras, A. El, O. Fochler, F. Reining, Z. Xu, CG. Focus week, HIC at the LHC, CERN , may 2007. Parton cascade with stochastic algorithm

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Space time evolution of QCD matter

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  1. Johann Wolfgang Goethe-Universität Frankfurt Institut für Theoretische Physik Space time evolution of QCD matter I. Bouras, A. El, O. Fochler, F. Reining, Z. Xu, CG Focus week, HIC at the LHC, CERN , may 2007 • Parton cascade with stochastic algorithm • Transport rates and momentum isotropization • Thermalization of gluons due to • Results: bottom-up scenario, jet-quenching, elliptic flow, viscosity,… viscous hydro, …

  2. Relativistic Quantum Transport for URHIC RHIC, LHC • microscopic transport calculations of partonic degrees of freedom new development Boltzmann Approach of MultiParton Scatterings (BAMPS) Z. Xu and C. Greiner, PRC 71, 064901 (2005) collision probability D3x particle in cell method

  3. parton scatterings in leading order pQCD J.F.Gunion, G.F.Bertsch, Phys. Rev. D 25, 746(1982) screening mass: LPM suppression: the formation time

  4. Example fugacity ~ 0.5

  5. Important scales for kinetic transport & simulations Simulations solve Boltzmann equation: → test particles and other schemes Semiclassical kinetic theory: (Quantum mechanics: )

  6. Initial production of partons minijets CGC string matter

  7. fast isotropization and thermalisation elliptic flow in noncentral Au+Au collisions at RHIC: Z. Xu and C. Greiner, hep-ph/0703233 Z. Xu and C. Greiner, NPA 774, 787 (2006) central hydrodynamical evolution of momentum spectrum, … micr. determination of transport parameter …

  8. 3+1dim. full cascade: comparison with RHIC data

  9. Z. Xu and C. Greiner, arXiv:hep-ph/0703233 The drift term is large. gg<->ggg interactions are essential for kinetic equilibration!

  10. transverse energy at y=0 in Au+Au central collision

  11. Initial condition with Color Glass Condensate h: [-0.05:0.05] and xt < 1.5 fm

  12. bottom-up scenario of thermalization R.Baier, A.H.Mueller, D.Schiff and D.T.Son, PLB502(2001)51 • Qs-1 << t << a-3/2 Qs-1 Hard gluons with momenta about Qs are freed • and phase space occupation becomes of order 1. • a-3/2 Qs-1 << t << a-5/2 Qs-1(h+h -> h+h+s) • Hard gluons still outnumber soft ones, but soft gluons give most of the • Debye screening. • a-5/2 Qs-1 << t << a-13/5 Qs-1 (h+h -> h+h+s; s+s -> s+s; h+s -> sh+sh+s) • Soft gluons strongly outnumber hard gluons. • Hard gluons loose their entire energy to the thermal bath. • After a-13/5 Qs-1 the system is thermalized: T ~ t-1/3, T0 ~ a2/5 Qs

  13. Not the full Bottom-Up story... evolution of particle number in bottom-up scenario in 1+1 dim. geometry LHC … RHIC • Particle number decreases in the very first moment • No net soft gluon production at early times!

  14. Evolution of temperature and spectrum … Andrej El

  15. extracting the viscosity preliminary Bjorken geometry:

  16. Jet-Quenching in a central Au Au collision at RHIC Oliver Fochler preliminary new: RAAhigher? old: RAA ~ 0.04–0.05 quarks not yet included …

  17. Summary • A new parton cascade including inelastic multiparton scatterings gg↔ggg • Explains thermalization and hydrodynamical expansion at RHIC • PQCD inspired gg↔ggg are important for the thermalization. • PQCD gg↔ggg generate the elliptic flow in noncentral collisions. • Not full bottom-up thermalization scenario with CGC • 3~4 too much jet-quenching Outlook • viscosity • including quarks, heavy quark production • Test for initial conditions (boundaries)

  18. possible Chromo/Weibel instabilities B.Schenke, A. Dumitru, Y. Nara, M. Strickland

  19. Initial conditions: minijets production with pt > p0 binary approximation  for a central Au+Au collision at RHIC at 200 AGeV using p0=2 GeV

  20. Results rapidity distribution

  21. the central region: h: [-0.5:0.5] and xt < 1.5 fm including gg<->ggg without gg<->ggg thermalization and hydrodynamical behavior NO thermalizationand free streaming

  22. … transport rates ! Why fast thermalization? transport cross section: gg -> gg gg -> ggg BUT! This is not the whole story...

  23. q(t) gives the timescale of kinetic equilibration.

  24. special case for isotropic distribution of collision angle

  25. momentum isotropization and kinetic equilibration Initial condition: Minijets p0=1.4 GeV

  26. Important scales for kinetic transport & simulations Simulations solve Boltzmann equation: → test particles and other schemes Semiclassical kinetic theory: (Quantum mechanics: )

  27. ... kinetic transport still valid

  28. Thermalization times: comparison with bottom-up prediction • 1/Qs behavior seems to be correct. • instead a-13/5 behavior but a-x with x < 13/5

  29. Jet-Quenching Box calculation: T=400MeV dominant process is 2->3 Oliver Fochler

  30. Bremsstrahlung processes LPM suppression: the formation time Bethe-Heitler regime varying the cut-off for kT:

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