QM2012, Washington, DC, Aug. 13-Aug. 18, 2012

Supported by DOE

08/13/2012

QGP viscosity at RHIC and LHC energies

Huichao Song

Thanks for discussions with U. Heinz, M.Luzum, H. Petersen, S.Moreland, L.Pang, Z.Qiu, C.Shen, R. Soltz, X.N. Wang …

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

How perfect is the QGP fluid?

0)( xT gpuupeT )()(

u

T

T

2

12

u

T

Tu

2

1)(

viscous hydrodynamics

)( p Input: “EOS”

Shear viscosity: Bulk viscosity:

Assume zero net baryon density & heat conductivity at RHIC and LHC

3+1-d: Mcgill(2011), MSU, Crakow(2012),

2+1-d: OSU, INT, Stony Brook, Pudue, Calcutta (2008), Crakow, Frankfurt(2010)

Nagoya (C. Nonaka , Parallel 3A,Wed).

Generic features of shear & bulk viscosities

acts against the buildup of flow anisotropy

acts against the buildup of radial

flow

Shear viscosity: Bulk viscosity:

acts against the buildup of flow anisotropy

acts against the buildup of radial

flow

Shear viscosity: Bulk viscosity:

The shear viscosity leads to a significant suppression of V2 (Romatsche & Romatsche PRL07; song & Heinz PLB08, PRC08; Dusling & Teaney PRC 08; Molnar & Huovinen JPG 08 … …)

Bulk viscous effects are much smaller than shear ones due to the critical slowing down near phase transition (Song & Heinz PRC09)

One can extract the QGP shear viscosity from exp data without large contamination from bulk viscosity

Visc. suppressionof elliptic flow

shear visc. shear+ bulk visc.

ideal

Song & Heinz PRC09

The shear viscosity tends to smear out the inhomogeneous structures, leading to a suppression of V3 (Schenke, Jeon & Gale PRL2011, PRC2012; Qiu & Heinz PRC2011; also see talks by B.Schenke; F. Gardim; Poster of Z. Qiu )

Viscous suppressionof triangular flow

viscous hydro evolution

ideal hydro evolution initial profile

Qiu & Heinz 2011

(B.Schenke)

-early attempts from viscous hydrodynamics

QGP viscosity at RHIC energies (2008)

Luzum & Romatschke, PRC 2008 Glauber KLN

Viscous hydro & QGP viscosity (2008)

)4/1(5/ s

-non-equilibrium chemical composition of HRG : (PCE vs. CE) ~100%

-transport properties of HRG (or equil. HRG vs. non-equil. HRG) : ~100-150%-bulk viscosity: ?%

Effects that are not included in this viscous hydro calculations

Glauber & KLN initializations lead to 100% uncertainties for the QGP shear viscosity

-later results from the VISHNU hybrid model

QGP viscosity at RHIC energies (2011)

VISHNU hybrid approach

Initial conditions viscous hydro (2+1d) hadron cascade

H. Song, S. Bass, U. Heinz, PRC2011

Tsw=165MeV

-3+1 d viscous hydro+ hadron cascade: S. Jeon , Parallel 2A ,Tue.

Other related developments

-EoS: (s95p-PCE) (Huovinen & Petreczky10)

-initial conditions

-chemical composition of HRG

-transport properties of HRG

-switching temperature:

Tsw=165MeV

HadronCascade

VISHNU:

-2+1 d vs 3+1 d viscous hydro: Shen, Schenke & Heinz on going work; Vredevoogd &Pratt, PRC85,044908(2012)

MC-KLN MC-Glauber

H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011

VISHNU hybrid model & QGP viscosity (2011)

-corrected exp. V2 data that remove non-flow & fluc. effects

-integrated V2 for all charged hadrons: In contrast to V2(PT), it is less sensitive to

)41(5.2)/()41(1 QGPs

bulk viscosity, corrections, radial flow & chemical composition of HRG f

The analysis uses:

MC-KLN MC-Glauber

H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011

VISHNU hybrid model & QGP viscosity (2011)

-Initial flow, bulk viscosity, single shot vs. e-b-e calculations

-Other uncertainties (much smaller)

)41(5.2)/()41(1 QGPs

(each of them shift V2 by a few percent, partial cancellation among them)

-Main uncertainties come from initial conditions

H.Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRC2011

further tests: for identified hadrons )(2 TpV

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%

08.0/ s

16.0/ s

Glauber Glauber

KLN KLN

Initialization models, pre-equilibrium dynamics & QGP viscosity

MC-KLN MC-Glauber

H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011

VISHNU hybrid model & QGP viscosity (2011)

Main uncertainties come from initial conditions

)41(5.2)/()41(1 QGPs

MC-KLN, larger HIGHER value of QGP viscosity

MC-Glauber, smaller LOWER value of QGP viscosity 22

MC-KLN & MC-Glauber initializations & V3

-triangular flow is sensitive to QGP shear viscosity, but NOT sensitive to MC-KLN or MC-Glauber initializations

Qiu & Heinz,2011

2

3

MC-KLN

MC-Glauber

see poster of Z. Qiu

Zhi & Heinz 2011

Viscous Hydro

MC-KLN & MC-Glauber initializations & V3 see poster of Z. Qiu Qiu, Shen & Heinz 2011Pure viscous hydro simulations :

V3 prefer lower value of QGPviscosity

22 / v 22 / v

33 / v 33 / v20.0/ KLN,MC s

20.0/ KLN,MC s 08.0/ Glb,MC s

08.0/ Glb,MC s

Initialization Models

-fluctuations of color charges (in the framework of CGC):

IP-Glasma: B. Schenke et al., arXiv:1202.6646; 1206.6805 [nucl-th] B. Schenke, Parallel 3A, Wed.

Correlated Fluctuation: B. Muller & A. Schafer, arXiv:1111.3347 [hep-ph] S. Moreland, Parallel 4D, Wed.

-fluctuations of local gluon numbers (in the famework of MC-KLN):

Multiplicity fluctuations: A. Dumitru and Y. Nara, Phys. Rev. C 85, (2012) 034907 A. Dumitru, plenary IC, Mon.

-fluctuations of nucleon positions:

MC-Glauber: MC-KLN:

T. Hirano & Y. Nara, Phys. Rev. C 79 064904 (2009) (used in the VISHNU hybrid model)

IP-GlasmaMultiplicity fluctuations

3

2

3

2

3

2

IP-GlasmaCorrelated fluctuations

Please also refer to talk of B. Schenke, S. Moreland & A. Dumitru

Schenke, et al. Moreland+ Heinz Dumitru +Nara

Multiplicity fluctuations

Correlated fluctuations

-early flow & fluctuations from dynamical models:

URQMD initialization: H.Petersen & M. Bleicher, Phys. Rev. C81, 044906,2010 H.Petersen, Plenary VA, Fri.

AMPT initialization: L. Pang, Q.Wang & X.Wang, arXiv:1205.5019[nucl-th] L. Pang, Parallel 4D, Wed.

EPOS/NEXUS initialization: K. Werner et al., Phys. Rev. C83:044915,2011; H. J. Drescher et, al., Phys.Rev. C65 , 054902 (2002) M. Nahrgang , poster section .

IP-Glasma: B. Schenke, et.al, arXiv:1202.6646; 1206.6805 [nucl-th] B. Schenke, Parallel 3A , Wed.

Free Streaming limit: G. Qin, et. al., Phys. Rev. C82 064903 (2010); OSU, on-going work

Pre-equilibrium dynamics

Hydro limit: OSU group, on-going work

Pre-equilibrium dynamics smoothes out fluctuations, reducing , but building radial flow 32 ,

-early flow & fluctuations from dynamical models:

URQMD initialization: H.Petersen & M. Bleicher, Phys. Rev. C81, 044906,2010 also refer to talk of H.Petersen on 17 Aug., Plenary VA

AMPT initialization: L. Pang, Q.Wang & X.Wang, arXiv:1205.5019[nucl-th] also refer to talk of L. Pang on 15 Aug., Parallel 4D

EPOS/NEXUS initialization: K. Werner et al., Phys. Rev. C83:044915,2011; H. J. Drescher ,et al., Phys.Rev. C65 , 054902 (2002) also refer to poster of M. Nahrgang on 16 Aug

IP-Glasma: B. Schenke, et.al, arXiv:1202.6646; 1206.6805 [nucl-th] B. Schenke , Parallel 3A

Pre-equilibrium dynamics

Petersen & Qiu, unpublished notes;please also refer to Phys.Rev. C82 041901 (2010)

Fluctuations in energy deposition slightly increase

3

32 ,

2

-early flow & fluctuations from dynamical models:

URQMD initialization: H.Petersen & M. Bleicher, Phys. Rev. C81, 044906,2010 also refer to talk of H.Petersen on 17 Aug., Plenary VA

AMPT initialization: L. Pang, Q.Wang & X.Wang, arXiv:1205.5019[nucl-th] also refer to talk of L. Pang on 15 Aug., Parallel 4D

EPOS/NEXUS initialization: K. Werner et al., Phys. Rev. C83:044915,2011; H. J. Drescher ,et al., Phys.Rev. C65 , 054902 (2002) also refer to poster of M. Nahrgang on 16 Aug

IP-Plasma: B. Schenke, et.al, arXiv:1202.6646; 1206.6805 [nucl-th] B. Schenke on 15 Aug., Parallel 3A

Pre-equilibrium dynamics

Early longitudinal flow fluctuations reduce V2

L. Pang, Q.Wang & X.Wang, arXiv:1205.5019[nucl-th]

-early flow & fluctuations from dynamical models:

URQMD initialization: H.Petersen & M. Bleicher, Phys. Rev. C81, 044906,2010 H.Petersen, Plenary VA, Fri.

AMPT initialization: L. Pang, Q.Wang & X.Wang, arXiv:1205.5019[nucl-th] L. Pang, Parallel 4D, Wed.

EPOS/NEXUS initialization: K. Werner et al., Phys. Rev. C83:044915,2011; H. J. Drescher ,et al., Phys.Rev. C65 , 054902 (2002) M. Nahrgang , Thur.

IP-Glasma: B. Schenke, et.al, arXiv:1202.6646; 1206.6805 [nucl-th] B. Schenke , Parallel 3A , Wed.

Free Streaming limit: G. Qin, et. al., Phys. Rev. C82 064903 (2010); OSU, on-going work

Pre-equilibrium dynamics

Hydro limit: OSU group, on-going work

Pre-equilibrium dynamics smooth out fluctuations, reducing , but building radial flow 32 ,

Mostly, the effects of pre-equilibrium dynamics was studied with ideal hydro. Their quantitative influences on are still unknown.QGPs)/(

QGP viscosity at LHC energies

V2 at RHIC and LHCSong, Bass & Heinz, PRC 2011

The average QGP viscosity is roughly the same at RHIC and LHC

for pions, kaons & protons at LHC

Nicely reproduce V2(PT) for all centrality bins at LHC byVISHNU hybrid model

20.0)/( QGPs

Heinz, Shen & Song, 2011VISHNU

)(2 TpV

for pions, kaons & protons at LHC

Results from pure viscous hydrodynamics (WITHOUT hadron cascade), results shown at QM2011

20.0/ s

Heinz, Shen & Song, 2011Viscous Hydro

)(2 TpV

for pions, kaons & protons at LHC

Viscous Hydro

VISHNU

A comparison between viscous hydrodynamics and VISHNU

Heinz, Shen & Song, 2011

)(2 TpV

))(/( TsTemperature dependent

V2(PT) at RHIC and LHC

Assuming const. s/

16.0/ s24.020.0/ s

RHIC: LHC:

Song, Bass & Heinz, PRC2011

Is QGP fluid more viscous for the temperature region covered by LHC?

One needs to investigate the temperature dependence of ))(/( Ts

Is QGP fluid more viscous at LHC ?

We can not constrain from v2 and spectra

Song, Bass & Heinz, PRC2011

)()/( Ts QGP

Results from Frankfurt group:

Elliptic flow is dominated by the hadronic viscosity at RHIC energies

H. Niemi, G.S. Denicol, P. Huovinen, E. Molnar, and D.H. Rischke, Phys. Rev. Lett.84, 011901(2011);arXiv:1203.2452[nucl-th]

))(/( Ts

Investigations from viscous hydro: C. Shen, U. Heinz, P. Huovinen, H.Song PRC2011

V2 is not only sensitive to but also sensitive to initialization of

))(/( Ts

Extra complications:

It is not an easy task to extract from experimental data

))(/( Ts

LHC

Current Developments

Extracting from Vn in ultra-central collisionssee talk of M. Luzum

s/

-In most central collisions, fluctuation effects are dominant (Geometry effects are suppressed)

-Additional features: fitting 2

Viscous Hydro

Higher Order Event Plane Correlations

qualitatively reproduce the measured event plane correlationsPure e-b-e viscous hydro simulations :

Qiu & Heinz, arXiv:1208.1200[nucl-th]

EXP. data:[ATLAS Collaboration], CERN preprint ATLAS-CONF-2012-049

spectra

HBT

elliptic flow

see poster of I. Garishvili

Spectra

R. Soltz, et al., arXiv:1208.0897[nucl-th]

Constraining initial temperature & shear viscosity from pion spectra, elliptic flow & HBT radii at 0-20% centrality with evolution. 2

Early CHIMERA Results(Comprehesive Heavy Ion Model

Evaluation and Reporting Algorithm)

Summary

(visc. hydro)V2

(visc. hydro)V2,V3

(VISHNU)V2

Uncertainties from initial quantum

fluc.

2008 early 2011 late2011 2012 year

?

QGPs)/(

)4/(1 )4/(2 )4/(3 )4/(4 )4/(5

Recent developments on initialization models:

color charge fluctuations; multiplicity fluctuations; initial flow fluctuations … …

This is a rapidly evolving area, much more at QM2014!

Recent developments on initialization models:

color charge fluctuations; multiplicity fluctuations; initial flow fluctuations … …

to implement e-b-e VISHNU to further study: triangular flow & higher order flow harmonics, higher-order event plane correlations … ...

This will help us to constrain initialization models, tightening the limit on

(visc. hydro)V2

(visc. hydro)V2,V3

(VISHNU)V2

Uncertainties from initial quantum

fluc.

2008 early 2011 late2011 2012 year

?

QGPs)/(

)4/(1 )4/(2 )4/(3 )4/(4 )4/(5

QGPs)/(

Thank you

Results from Frankfurt group:

H. Niemi, G.S. Denicol, P. Huovinen, E. Molnar, and D.H. Rischke, Phys. Rev. Lett.84, 011901(2011);arXiv:1203.2452[nucl-th]

))(/( Ts

Effective Hadronic viscosity from VISHNU

Song, Bass & Heinz PRC2011

e-b-e hydro vs. single shot hydro

see talk of M. Luzum