New Results from Viscous Hydro + URQMD (VISHNU) International School for High Energy Nuclear...

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, 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)

1H. Song, S. Bass, U. Heinz, Phys Rev. C83 054912(2011)

Huichao Song 宋慧超

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

How perfect the QGP fluid is? 2

0)( xT

S.Bass

gpuupeT )()(

u

T

T

2

12

u

T

Tu

2

1)(

viscous hydrodynamics

)( p Input: “EOS”

3

0)( xT gpuupeT )()(

u

T

T

2

12

u

T

Tu

2

1)(



4

0)( xT

S.Bass

gpuupeT )()(

u

T

T

2

12

u

T

Tu

2

1)(

pre-equilibrium dynamics + viscous hydro + hadron cascade


Initial conditions + viscous hydro (QGP) + hadron cascade (HRG)

Initial conditions + viscous hydro (QGP & HRG) + final conditions


5

Viscous hydro: Shear viscosity & elliptic flow V2

20-25% v2 suppression

4

1

s

Elliptic flow v2

-V2 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

...])2cos(),(21[2

12

3

bpvdpdyp

dN

ddpdyp

dN

pd

dNE

TTT

TT

(GeV)Tp0 1

~30%

Partially Chemical equil.

Ideal hydro

P. Huovinen 07

Hadronic effects on elliptic flow V2 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 v2 suppression

s95p-PCE

v2 suppression increases from ~20% (min visc hydro) to ~30% (min visc hydro + URQMD)

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 V2

~100% uncertainties for the extracted QGP viscosity

V2 from different exp methods are affected by non-flow and fluctuations

~20%

Extracting QGP viscosity from RHIC data

EXP.

10

Ollitrault, Poskanzer & Voloshin, PRC09Corrected 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 s/

Corrected V2


EXP.

11

-initial conditions-EoS: s95p-PCE Huovinen & Petreczky10

-chemical composition of HRG -viscosity of HRG-bulk viscosity: <20%

Viscous Hydro + URQMD


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

),,(, 00 yxs

v2 is sensitive to the initial conditions

dydNSv /)/1(/2

-EoS: s95p-PCE Huovinen & Petreczky10


Song & Heinz, PRC 09

13


: : QGP viscosity dydNSv /)/1(/2

dydNSv /)/1(/2 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, PRL2011

14

theoretical vs. experimental

dydNSv /)/1(/2

---QGP viscosity

Ollitrault, Poskanzer & Voloshin, PRC09

- Corrected V2 in participant plan

Exp. Corrected V2

in part. plan

dydNSv /)/1(/2

S, - Glauber / fKLN (part. plan)

- dN/dy : STAR data 08

15

QGP viscosity from dydNSv /)/1(/2

24.016.0/ s for MC-KLN initial conditions

for MC-Glauber initial conditions 16.008.0/ s

MC-KLN MC-Glauber(Part. Plan) (Part. Plan)

16H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011

QGP viscosity from dydNSv /)/1(/2



effects from bulk viscosity effects from initial flow

MC-KLN (Part. Plan) (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, PRC2011

18

24.016.0/ s for KLN initial condi.for Glauber initial condi.16.008.0/ s

-hit the lower-bound of extracted from (non flow effects) dydNSv /)/1(/2 s/ -fluctuating effects is reduced by comparing theory & EXP. /2v

22 /}2{ v

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

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

19

QGP viscosity at RHIC & LHC energies

20

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

ALICE collaboration arXiv:1011.3914[nucl-ex]

V2(PT) at RHIC and LHC

Assuming const. s/

16.0/ s 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


V2(PT) at RHIC and LHC

Assuming const. s/

This is not aim for extracting QGP viscosity at LHC energy with reliable uncertainty estimates

16.0/ s Approximately fit STAR v2{4}, but over predict ALICE v2{4}

16.0/ s24.020.0/ s

RHIC:LHC:

22


Is QGP fluid more viscous at LHC ?

Weakly coupled QGP

Lattice results

Assuming const. s/

)2(16.0/ cc TTs )3(24.0/ cc TTs

RHIC:LHC:

?

23


Is QGP fluid more viscous at LHC ?

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 ! 24


A short summary- is sensitive to

Extraction from elliptic flow data using viscous hydro + UrQMD indicates:

)41(3/)41(1 ss/

s/2v

)4/1()21(/ s

-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: )4/1()32(/ s

25

Similar averaged QGP viscosity at RHIC and LHC energies

s/

HBT

V2

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



initial flow, bulk viscosity and e-b-e hydro:cancelation among them each of them shifts v2 by a few percent

Thank You

32

Thank You

33

HBT radii

sideout RR /- is sensitive to the QGP viscosity

- HBT HELPS to constrain the QGP viscosity, together with other observables (V2 …)

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 PT-spectra is stronger for photons than hadrons

K. Dusling, 0903

20 ~/T

pp

peff

Photon spectra

1

~sTpe

-Photon spectra MAY HELP to constrain the 2-d range of QGP viscosity & thermalization time, together with other observables (V2 …)

-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:1009.3244 [hep-ph]

36

Triangular flow & QGP viscosity

-triangular flow is sensitive to QGP shear viscosity

Schenke, Jeon & Gale,arXiv:1009.3244 [hep-ph]

-triangular flow may help us to eliminate the uncertainties from KLN and Glauber

Zhi & Heinz, preliminary results

2

3

MC-KLN

MC-Glauber

37

LHC

38

& initialization models dydNSv /)/1(/2 Glauber

S, from MC- glauber (smearing) with finite nucleon size

from MC- glauber with very small nucleon size (delta function)

S,

The slope of theoretical curves is un-favor the early MC-Glauber model (with delta fun. )

dydNSv /)/1(/2

(used by some EXP. Group )

(used by our theoretical Cal)

39

Uncertainties from bulk viscosity

fm/c120)/( s

1C3.1C

1C100C

N-S initialization Zero initialization

-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.)

Song & Heinz, 0909

s/uncertainties to ~20% (N-S initial.) <15% (zero initial.)

fm/c120)/( s

s/ s/

40

New Results from Viscous Hydro + URQMD (VISHNU) International School for High Energy Nuclear...

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Transcript of New Results from Viscous Hydro + URQMD (VISHNU) International School for High Energy Nuclear...