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

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

S.Bass viscous hydrodynamics Input: “EOS” 3

viscous hydrodynamics Input: “EOS” 4

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

Viscous hydro: Shear viscosity & elliptic flow V % v 2 suppression Elliptic flow v 2 - V 2 can 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. H. Song and U. Heinz, PRC08 6

~30% Partially Chemical equil. Ideal hydro P. Huovinen 07 Hadronic effects on elliptic flow V 2 hadronic dissipative effects ~30-50% -These two HRG effects are not included in early viscous hydro calculations T. Hirano 06 viscous hydro + hadron cascade (URQMD) hybrid approach URQMD includes the partially chemical equilibrium nature & hadronic dissipative effects 7

viscous hydro vs. viscous hydro + hadron cascade 8

viscous v 2 suppression s95p-PCE v 2 suppression increases from ~20% (min visc hydro) to ~30% (min visc hydro + URQMD) viscous hydro (QGP) + URQMD (HRG) viscous hydro (QGP) + URQMD (HRG) viscous hydro (QGP & HRG) ideal hydro (QGP & HRG) H. Song, S. Bass & U. Heinz, PRC11 20%30% 9

STAR DATA ~20% uncertainties in EXP V 2 ~100% uncertainties for the extracted QGP viscosity V 2 from different exp methods are affected by non-flow and fluctuations ~20% Extracting QGP viscosity from RHIC data EXP. 10

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 Corrected V 2 Extracting QGP viscosity from RHIC data EXP. 11

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

-initial conditions -chemical composition of HRG -viscosity of HRG -bulk viscosity: <20% Viscous Hydro + URQMD initial conditions - Glauber / KLN initializations - Fluctuation effects Constrained from dN/dy and spectra - initial flow v 2 is sensitive to the initial conditions -EoS: s95p-PCE Huovinen & Petreczky10 Extracting QGP viscosity from RHIC data Song & Heinz, PRC Song, Bass & Heinz, PRC2011

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

theoretical vs. experimental ---QGP viscosity Ollitrault, Poskanzer & Voloshin, PRC09 - Corrected V 2 in participant plan Exp. Corrected V 2 in part. plan - Glauber / fKLN (part. plan) - dN/dy : STAR data 08 15

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

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

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

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

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

V 2 (P T ) at RHIC and LHC Assuming const. Approximately fit STAR v2{4}, but over predict ALICE v2{4} This is not aim for extracting QGP viscosity at LHC energy with reliable uncertainty estimates 21 Song, Bass & Heinz, PRC2011

V 2 (P T ) at RHIC and LHC 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} RHIC: LHC: 22 Song, Bass & Heinz, PRC2011

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

Is QGP fluid more viscous at LHC ? We do not have enough evidence from v 2 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 ! 24 Song, Bass & Heinz, PRC2011

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

HBT V2V2 Spectra Other free inputs in the hybrid model Photons 26

e-b-e hydro vs. single shot hydro Event-by-event hydro produces 5% less v2/ecc than single- shot hydro with smooth averaged initial profile Zhi & Heinz, preliminary results 27 for MC-KLN initial conditions for MC-Glauber initial conditions initial flow, bulk viscosity and e-b-e hydro: cancelation among them each of them shifts v 2 by a few percent

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HBT radii - is sensitive to the QGP viscosity - HBT HELPS to constrain the QGP viscosity, together with other observables ( V 2 …) S. Pratt QM09 with viscosity without viscosity - However, viscosity is only one of the many ingredients that affect HBT radii (Pratt QM09) 34

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

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

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

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

Uncertainties from bulk viscosity N-S initializationZero initialization -with a critical slowing down, effects from bulk viscosity effects are much smaller than from shear viscosity bulk viscosity influences V 2 ~5% (N-S initial.) <4% (zero initial.) Song & Heinz, 0909 uncertainties to ~20% (N-S initial.) <15% (zero initial.) 40