New Results from Viscous Hydro + URQMD (VISHNU)

1. QGP viscosity at RHIC and LHC energies New Results from Viscous Hydro + URQMD (VISHNU) Huichao Song 宋慧超 International School for High Energy Nuclear Collisions , Wuhan, Oct 31- Nov.5, 2011 Supported by DOE References: H. Song , S. Bass and U. Heinz, Phys. Rev. C83, 024912 (2011) H. Song, S. Bass, U. Heinz, T. Hirano and C. Shen, Phys. Rev. Lett. 106, 192301(2011) H. Song, S. Bass, U. Heinz, T. Hirano and C. Shen, Phys. Rev. C83, 054910(2011) H. Song, S. Bass, U. Heinz, Phys Rev. C83 054912(2011) 11/04/2011

2. QGP-the most perfect fluid in the world? BNL News, 2005 How perfect the QGP fluid is?

3. viscous hydrodynamics Input: “EOS” hydro S.Bass

4. viscous hydrodynamics Input: “EOS”

5. viscous hydrodynamics S.Bass Input: “EOS” hydro pre-equilibrium dynamics + viscous hydro+ hadron cascade Initial conditions + viscous hydro(QGP & HRG) + final conditions Initial conditions + viscous hydro (QGP) + hadron cascade (HRG)

6. Viscous hydro: Shear viscosity & elliptic flow V2 H. Song and U. Heinz, PRC08 Elliptic flow v2 20-25% v2 suppression -V2can be used to extract the QGP shear viscosity -For an accurate extraction of QGP viscosity, one needs to control the theoretical uncertainties as well as precise exp data.

7. Hadronic effects on elliptic flow V2 hadronic dissipative effects Partially Chemical equil. Ideal hydro ~30% ~30-50% T. Hirano 06 P. Huovinen 07 -These two HRG effects are not included in early viscous hydro calculations viscous hydro+ hadron cascade (URQMD) hybrid approach URQMD includes the partially chemical equilibrium nature& hadronic dissipative effects

8. viscous hydro vs. viscous hydro + hadron cascade

9. viscous v2 suppression H. Song, S. Bass & U. Heinz, PRC11 ideal hydro (QGP & HRG) 20% 30% viscous hydro(QGP & HRG) viscous hydro (QGP) + URQMD (HRG) s95p-PCE v2 suppression increases from ~20% (min visc hydro) to ~30% (min visc hydro + URQMD)

10. Extracting QGP viscosity from RHIC data EXP. ~20% V2 from different exp methods are affected by non-flow and fluctuations STAR DATA ~20% uncertainties in EXP V2 ~100% uncertainties for the extracted QGP viscosity

11. Extracting QGP viscosity from RHIC data EXP. Corrected v2: Ollitrault, Poskanzer & Voloshin, PRC09 Corrected V2 with assumptions on fluctuations and non flow, all corrected v2 in participant / reaction plan converge to unique curves greatly reduces uncertainties from EXP data for the extracted

12. Extracting QGP viscosity from RHIC data Theoretical Modeling -initial conditions -EoS: s95p-PCE Huovinen & Petreczky10 -chemical composition of HRG -viscosity of HRG Viscous Hydro + URQMD -bulk viscosity: <20% Song, Bass & Heinz, PRC2011 Song & Heinz, PRC 09

13. Extracting QGP viscosity from RHIC data -initial conditions -chemical composition of HRG initial conditions -viscosity of HRG Viscous Hydro + URQMD -EoS: s95p-PCE Huovinen & Petreczky10 -bulk viscosity: <20% - Glauber / KLN initializations - Fluctuation effects Song, Bass & Heinz, PRC2011 Constrained from dN/dy and spectra Song & Heinz, PRC 09 - initial flow v2 is sensitive to the initial conditions

14. : : QGP viscosity H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011 is insensitive to initial conditions, but sensitive to the QGP viscosity in viscous hydro +URQMD calculations

15. theoretical vs. experimental ---QGP viscosity Ollitrault, Poskanzer & Voloshin, PRC09 Corrected V2 in part. plan Exp. - Corrected V2 in participant plan - dN/dy : STAR data 08 - Glauber / fKLN (part. plan)

16. QGP viscosity from MC-KLN MC-Glauber (Part. Plan) (Part. Plan) for MC-KLNinitial conditions for MC-Glauber initial conditions H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011

17. QGP viscosity from MC-KLN MC-Glauber (Part. Plan) (Part. Plan) effects from initial flow effects from bulk viscosity for MC-KLNinitial conditions for MC-Glauber initial conditions

18. H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRC2011 -a nice fit for both pion and proton spectra, insensitive to QGP viscosity

19. H.Song, S. Bass , U. Heinz, T. Hirano, and C. Shen, PRC2011 5-10% 5-10% 20-30% 20-30% 20-30% 20-30% 30-40% 30-40% 30-40% 30-40% 40-50% 40-50% 40-50% 40-50% Glauber Glauber KLN KLN -fluctuating effects is reduced by comparing theory & EXP. -hit the lower-bound of extracted from (non flow effects) for KLN initial condi. for Glauber initial condi.

20. QGP viscosity at RHIC & LHC energies -- H. Song, S. Bass, U. Heinz, PRC2011 ALICE collaboration arXiv:1011.3914[nucl-ex]

21. V2(PT) at RHIC and LHC Song, Bass & Heinz, PRC2011 Assuming const. This is not aim for extracting QGP viscosity at LHC energy with reliable uncertainty estimates Approximately fit STAR v2{4}, but over predict ALICE v2{4}

22. V2(PT) at RHIC and LHC Song, Bass & Heinz, PRC2011 Assuming const. RHIC: LHC: This is not aim for extracting QGP viscosity at LHC energy with reliable uncertainty estimates Approximately fit STAR v2{4}, but over predict ALICE v2{4}

23. Is QGP fluid more viscous at LHC ? Song, Bass & Heinz, PRC2011 Assuming const. RHIC: ? LHC: Weakly coupled QGP Lattice results

24. Is QGP fluid more viscous at LHC ? Song, Bass & Heinz, PRC2011 We do not have enough evidence from v2 and spectra alone At this moment, it is an open issue on whether QGP fluid is more viscous or perfect in temperature region covered by LHC !

25. A short summary - is sensitive to Extraction from elliptic flow data using viscous hydro + UrQMD indicates: Similar averaged QGP viscosity at RHIC and LHC energies -Relatively larger uncertainties are from initial geometry MC-Glauber: MC-KLN: -Relatively smaller uncertainties are from initial flow, bulk viscosity, single short hydro vs. e-by-e simulations … -other possible observables may help to reduce these uncertainties , photons,HBT radii, triangular flow …

26. Photons HBT V2 Spectra Other free inputs in the hybrid model

27. e-b-e hydro vs. single shot hydro Zhi & Heinz, preliminary results Event-by-event hydro produces 5% less v2/ecc than single-shot hydro with smooth averaged initial profile each of them shifts v2 by a few percent initial flow, bulk viscosity and e-b-e hydro: cancelation among them for MC-KLNinitial conditions for MC-Glauber initial conditions

32. Thank You

33. Thank You

34. HBT radii S. Pratt QM09 without viscosity with viscosity - is sensitive to the QGP viscosity - However, viscosity is only one of the many ingredients that affect HBT radii (Pratt QM09) - HBT HELPS to constrain the QGP viscosity, together with other observables (V2 …)

35. EM probes: Photons Photon spectra Pion spectra K. Dusling, 0903 -Viscous hardening of PT-spectra is stronger for photons than hadrons -However, earlier thermalization also leads to harder photon spectra (Dusling 0903) -Photon spectra MAY HELP to constrain the 2-d range of QGP viscosity & thermalization time, together with other observables (V2 …)

36. Triangular flow & QGP viscosity Schenke, Jeon & Gale, arXiv:1009.3244 [hep-ph] -triangular flow is sensitive to QGP shear viscosity

37. Triangular flow & QGP viscosity Schenke, Jeon & Gale, arXiv:1009.3244 [hep-ph] MC-KLN MC-Glauber Zhi & Heinz, preliminary results -triangular flow is sensitive to QGP shear viscosity -triangular flow may help us to eliminate the uncertainties from KLN and Glauber

38. LHC

39. & initialization models Glauber from MC- glauber (smearing) with finite nucleon size (used by our theoretical Cal) from MC- glauber with very small nucleon size (delta function) (used by some EXP. Group ) The slope of theoretical curves is un-favor the early MC-Glauber model (with delta fun. )

40. Uncertainties from bulk viscosity N-S initialization Zero initialization Song & Heinz, 0909 -with a critical slowing down , effects from bulk viscosity effects are much smaller than from shear viscosity bulk viscosity influences V2~5% (N-S initial.)<4% (zero initial.) uncertainties to ~20% (N-S initial.) <15% (zero initial.)