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QCD Plasma Equilibration, Collective Flow Effects and Jet-Quenching – Phenomena of Common Origin

Johann Wolfgang Goethe-Universität Frankfurt Institut für Theoretische Physik. QCD Plasma Equilibration, Collective Flow Effects and Jet-Quenching – Phenomena of Common Origin. C. Greiner , 24th winter workshop on nuclear dynamics, South Padre Island, 2008. in collaboration with

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QCD Plasma Equilibration, Collective Flow Effects and Jet-Quenching – Phenomena of Common Origin

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  1. Johann Wolfgang Goethe-Universität Frankfurt Institut für Theoretische Physik QCD Plasma Equilibration, Collective Flow Effects and Jet-Quenching –Phenomena of Common Origin C. Greiner, 24th winter workshop on nuclear dynamics, South Padre Island, 2008 • in collaboration with A. El, O. Fochler, B. Schenke, H. Stöcker, Zhe Xu

  2. Y X Three body effects in parton cascades! • Fast Thermalization from QCD: 3-2 important! • Equilibr. time short in 2-3! • Elliptic flow v2 high in 2-3! • Viscosity small ~ 0.08! • RAA,gluon~ 0.1 ! from R. Bellwied P.Huovinen et al., PLB 503, 58 (2001)

  3. Initial production of partons minijets color glass condensate string matter

  4. Momentum space anisotropy:Time dependence Michael Strickland

  5. Thermalization driven byplasma instabilities Refs.: Mrowczynski; Arnold, Lenaghan, Moore, Yaffe; Rebhan, Romatschke, Strickland, Bödeker, Rummukainen; Dumitru, Nara; Berges, Scheffler, Sexty Dumitru, Nara, Strickland, PRD 75, 025016 (2007) Dumitru, Nara, Schenke, Strickland, arXiv:0710.1223

  6. QCD thermalization using parton cascade VNI/BMS: K.Geiger and B.Müller, NPB 369, 600 (1992) S.A.Bass, B.Müller and D.K.Srivastava, PLB 551, 277(2003) ZPC: B. Zhang, Comput. Phys.Commun. 109, 193 (1998) MPC: D.Molnar and M.Gyulassy, PRC 62, 054907 (2000) AMPT: B. Zhang, C.M. Ko, B.A. Li, and Z.W. Lin, PRC 61, 067901 (2000) BAMPS: Z. Xu and C. Greiner,PRC 71, 064901 (2005); 76, 024911 (2007)

  7. BAMPS: BoltzmannApproachofMultiPartonScatterings A transport algorithm solving the Boltzmann-Equations for on-shell partons with pQCD interactions new development ggg gg, radiative „corrections“ (Z)MPC, VNI/BMS, AMPT Elastic scatterings are ineffective in thermalization ! Inelastic interactions are needed ! Xiong, Shuryak, PRC 49, 2203 (1994) Dumitru, Gyulassy, PLB 494, 215 (2000) Serreau, Schiff, JHEP 0111, 039 (2001) Baier, Mueller, Schiff, Son, PLB 502, 51 (2001)

  8. screened partonic interactions in leading order pQCD elastic part radiative part J.F.Gunion, G.F.Bertsch, PRD 25, 746(1982) T.S.Biro at el., PRC 48, 1275 (1993) S.M.Wong, NPA 607, 442 (1996) screening mass: LPMsuppression: the formation time Lg: mean free path

  9. distribution of collision angles at RHIC energies gg gg: small-angle scatterings gg ggg: large-angle bremsstrahlung

  10. pT spectra at collision center: xT<1.5 fm, Dz < 0.4 t fm of a central Au+Au at s1/2=200 GeV Initial conditions: minijets pT>1.4 GeV; coupling as=0.3 simulation pQCD 2-2 + 2-3 + 3-2 simulation pQCD, only 2-2 3-2 + 2-3: thermalization! Hydrodynamic behavior! 2-2: NOthermalization

  11. pT spectra Initial conditions: Color Glass Condensate Qs=3 GeV; coupling as=0.3 A.El, Z. Xu and CG, arXiv: 0712.3734 [hep-ph] ggg gg ! This 3-2 is missing in the Bottom-Up scenario (Baier, Dohkshitzer, Mueller, Son (2001)). Bottom up is not working as advocated: no tremendous soft gluon production, soft modes do not thermalize before the hard modes

  12. time scale of thermalization Theoretical Result ! t = time scale of kinetic equilibration.

  13. What determines the equilibration time scale t ? Cross section doesnotdetermine t! Z. Xu and CG, arXiv: 0710.5719 [nucl-th]

  14. BUT, this isnotthefull story !

  15. Transport Rates Z. Xu and CG, PRC 76, 024911 (2007) • Transport rate is the correct quantity describing kinetic • equilibration. • Transport collision rates have an indirect relationship • to the collision-angle distribution.

  16. Transport Rates Large Effect of 2-3 !

  17. Shear Viscosity h Z. Xu and CG, arXiv: 0710.5719 [nucl-th] From Navier-Stokes approximation From Boltzmann-Eq. relation between h and Rtr

  18. Ratio of shear viscosity to entropy density in 2-3 AdS/CFT RHIC Z. Xu, A. El

  19. Collective Effects transverse flow velocity of local cell in the transverse plane of central rapidity bin Au+Au b=8.6 fm using BAMPS =c

  20. Elliptic Flow and Shear Viscosity in 2-3 at RHIC 2-3Parton cascade BAMPS Z. Xu, CG, H. Stöcker, arXiv: 0711.0961 [nucl-th] viscous hydro. Romatschke, PRL 99, 172301,2007 h/s at RHIC > 0.08 Z. Xu

  21. Rapidity Dependence of v2: Importance of 2-3! BAMPS evolution of transverse energy

  22. Dissipative Hydrodynamics Shear, bulk viscosity and heat conductivity of dense QCD matter could be prime candidates for the next Particle Data Group, if they can be extracted from data. Need a causal hydrodynamical theory. What are the criteria of applicability? Causal stable hydrodynamics can be derrived from the Boltzmann Equation: -Renormalization Group Method by Kunihiro/Tsumura-->stable 1st Order linearized BE with f=f0+εf1+ε²f2 yields (2nd Order – work in progress) can be solved by introducing projector P on Ker{A}, where A-linearized collision operator -Grad‘s 14-momentum method-->2nd Order causal hydrodynamics. Calculate momenta of the BE. Transport coefficients and relaxation times for dissipative quantities can be calculated as functions of collision terms in BE. Compare dissipative relaxation times to the mean free pass from cascade simulation. Andrej El

  23. Hard probes of the medium • nuclear modification factor relative to pp (binary collision scaling) • experiments show approx. factor 5 of suppression in hadron yields high energy particles are promising probes of the medium created in AA-collisions QM 2008, T. Awes

  24. transport model: incoherent treatment ofggggg processes • parent gluon must not scatter during formation time of emitted gluon • discard all possible interference effects (Bethe-Heitler regime) p1 p2 kt kt lab frame CM frame t = 1 / kt • total boost LPM-effect O. Fochler

  25. first realistic 3d results on jet-quenching with BAMPS LPM cut-off increases dE/dx, static medium (T = 400 MeV) <qT2/l>, static medium (T = 400 MeV) nuclear modification factor central (b=0 fm) Au-Au at 200 AGeV RAA ~ 0.1 cf. S. Wicks et al. Nucl.Phys.A784, 426 O. Fochler

  26. Jet propagation within YM fields Dynamical simulation of jet propagation in the plasma preliminary Poynting vectors Björn Schenke

  27. Additional near-side long range correlation in  (“ridge like” corrl.) observed. Dan Magestro, Hard Probes 2004, STAR, nucl-ex/0509030, Phys. Rev. C73 (2006) 064907 and P. Jacobs, nucl-ex/0503022 Explaining the “ridge” Au+Au 0-10% STAR preliminary J. Putschke, QM2006 Stronger longitudinal broadening caused by domains of strong chromo-fields with Dumitru, Nara, Schenke, Strickland e-Print: arXiv:0710.1223 [hep-ph]

  28. Summary Inelastic/radiative pQCD interactions (23 + 32) explain: • fast Thermalization • large Collective Flow • small shear Viscosity of QCD matter at RHIC • realistic jet-quenching of gluons Future/ongoing analysis and developments: • light and heavy quarks • jet-quenching (Mach Cones, ridge) • hadronisation and afterburning (UrQMD) needed to determine how imperfect the QGP at RHIC and LHC can be • dissipative hydrodynamics

  29. Au+Au – Setup • central (b=0 fm) Au-Au collision at 200 AGeV • sampling of initial gluon plasma: • initial momentum distribution (mini-jets) according to • Glück-Reya-Vogt parameterization for structure functions; K = 2 • lower cut-off: p0 = 1.4 GeV (reproduces dET/dy) • particle production via standard nuclear geometry(Wood-Saxon density profile, Glauber-Model) • each parton is given a formation time • 35 testparticles • simulate evolution of fireball up to ~5 fm/c • when energy density in a cell drops below e=1 GeV • free streaming (in the respective cell)

  30. Initial conditions Glauber-type: Woods-Saxon profile, binary nucleon-nucleon collision minijets production with pt > p0 for a central Au+Au collision at RHIC at 200 AGeV using p0=1.4 GeV

  31. P.Danielewicz, G.F.Bertsch, Nucl. Phys. A 533, 712(1991) A.Lang et al., J. Comp. Phys. 106, 391(1993) Stochastic algorithm cell configuration in space D3x for particles in D3x with momentum p1,p2,p3 ... collision probability:

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

  33. ... kinetic transport still valid

  34. The drift term is large. gg<->ggg interactions are essential for kinetic equilibration!

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

  36. 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

  37. Au-Au – Reconstruction • partons with high-pt too rare • simulate large number of initial conditions • select events according to highest pt-(test)particle • simulate only selected events and weight results full: 200000 events; reconstruction: 40 events per pt-bin, ~1000 total

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