1 / 28

Shear Viscosity and Collective Flow in Heavy Ion Collisions within Parton Cascade Calculations

Shear Viscosity and Collective Flow in Heavy Ion Collisions within Parton Cascade Calculations. Zhe Xu, Carsten Greiner. Institut für Theoretische Physik Goethe-Universität Frankfurt, Germany. Trento, Sept. 17, 2009. Y. X. Motivation: how small is the QGP viscosity at RHIC?.

perrin
Download Presentation

Shear Viscosity and Collective Flow in Heavy Ion Collisions within Parton Cascade Calculations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Shear Viscosity and Collective Flow in Heavy Ion Collisions within Parton Cascade Calculations Zhe Xu, Carsten Greiner Institut für Theoretische Physik Goethe-Universität Frankfurt, Germany Trento, Sept. 17, 2009

  2. Y X Motivation: how small is the QGP viscosity at RHIC? P.Huovinen et al., PLB 503, 58 (2001) Viscous Hydrodynamics Muronga Luzum / Romatschke Song / Heinz Teaney / Dusling Molnar / Niemi / Rischke Kinetic Transport Model (Z)MPC: Zhang / Molnar / Gyulassy AMPT: Lin / Chen / Ma / Ko UrQMD: Petersen, Bleicher et al. BAMPS: Xu, Greiner et al. Zhe Xu, Trento 2009

  3. Outline • Parton Cascade BAMPS • Elliptic Flow at RHIC • Extracting h/s • v2(pT) • Summary Zhe Xu, Trento 2009

  4. Transport Model BAMPS: BoltzmannApproachofMultiPartonScatterings A transport algorithm solving the Boltzmann-Equations for on-shell partons with pQCD interactions new development ggg gg (Z)MPC, VNI/BMS, AMPT, PACIAE Elastic scatterings are ineffective in thermalization ! Inelastic interactions are needed ! Zhe Xu, Trento 2009

  5. Stochastic algorithm ZX and C. Greiner,PRC 71, 064901 (2005) y Space is divided into small cells ! x D3x collision probability -- stochastic Zhe Xu, Trento 2009

  6. screened pQCD based partonic interactions J.F.Gunion, G.F.Bertsch, PRD 25, 746(1982) LPMsuppression: treatment for incoherent interactions: the formation time Lg: mean free path Zhe Xu, Trento 2009

  7. Results: Transverse Energy in Au+Au at RHIC Initial conditions: gluon minijets production in independent binary NN collisions Zhe Xu, Trento 2009

  8. Elliptic Flow at RHIC using BAMPS ZX, Greiner, Stöcker, PRL 101, 2008 gg<->ggg processes generate large elliptic flow ! Zhe Xu, Trento 2009

  9. Zhe Xu, Trento 2009

  10. Shear Viscosity I Navier-Stokes approximation Boltzmann-Eq. AMY, JHEP 11 (2000) solve f1(x,p) using the variational method, which determines the coefficients of the functions of p in f1(x,p) Zhe Xu, Trento 2009

  11. ZX and C.Greiner, PRL 100, 172301, (2008) transport rate ZX and C. Greiner, PRC 76, 024911 (2007) Zhe Xu, Trento 2009

  12. Transport Rates Zhe Xu, Trento 2009

  13. distribution of collision angles at RHIC energies gg gg: small-angle scatterings gg ggg: large-angle bremsstrahlung central plateau Zhe Xu, Trento 2009

  14. Elliptic Flow and Shear Viscosity at RHIC viscous hydro. Romatschke, PRL 99, 2007 2-3Parton cascade BAMPS ZX, Greiner, Stöcker, PRL 101, 2008 h/s at the collision center h/s > 0.08 Zhe Xu, Trento 2009

  15. Shear Viscosity II A. El, A. Muronga, ZX and C. Greiner, PRC 79, 044914 (2009) Grad´s method Zhe Xu, Trento 2009

  16. Zhe Xu, Trento 2009

  17. comparison = 0 in chemical equilibration For minijets initial conditions: No kinetic equilibrium No chemical equilibrium Zhe Xu, Trento 2009

  18. Uncertainty: dependence of v2 on freeze-out condition generate the same elliptic flow. Therefore, h/sbetween 0.08 and 0.16. Zhe Xu, Trento 2009

  19. V2(pT) lower than data ZX and C. Greiner, PRC 79, 014904 (2009) Zhe Xu, Trento 2009

  20. e does not depend on Nd. If changing Nd from 16 to 40 (gluons+quarks with 2 flavors), <pT> ~ e/n decreases by a factor of 1.26. Zhe Xu, Trento 2009

  21. Including `quarks´ in BAMPS Assume: Quark dynamics is as same as the gluon one. Changing the degrees of freedom of gluons 16 to 40 (gluons+quarks with 2 flavors) Zhe Xu, Trento 2009

  22. Including `quarks´ 15% effect instead of 26% due to imcomplete chemical equilibration Zhe Xu, Trento 2009

  23. Summary Inelastic pQCD based interactions (23 + 32) explain: • Large Collective Flow • Small shear Viscosity of QCD matter at RHIC h/s: 0.08 ~ 0.2 Uncertainties of h/s: freezeout conditions, initial conditions, quark dynamics, hadronization, hadron cascade v2(pt) and v2 do not match data simultanously: need better understanding of quark dynamics and hadronization Zhe Xu, Trento 2009

  24. Variational method: AMY, JHEP 11 (2000) f1 to be solved. Zhe Xu, Trento 2009

  25. The maximun value of (c,S) –(c,Cc)/2 occurs when c satisfied the linearized BE. Zhe Xu, Trento 2009

  26. Transport Rates ZX and C. Greiner, 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. Zhe Xu, Trento 2009

  27. Zhe Xu, Trento 2009

  28. De Broglie length over mean free path Changing the mean free path by the inverse of the transport rate will lower the ratios. Zhe Xu, Trento 2009

More Related