CGC, Full 3D Hydro, CGC, Full 3D Hydro, and Hadronic and Hadronic

CascadeCascade

Tetsufumi HiranoTetsufumi Hirano

Department of Physics, University of TokyoDepartment of Physics, University of TokyoTH, U.Heinz, D.Kharzeev, R.Lacey, and Y.Nara, TH, U.Heinz, D.Kharzeev, R.Lacey, and Y.Nara, Phys.Lett.B636(2006)299,Phys.Lett.B636(2006)299,See also, TH and M.Gyulassy, Nucl.Phys.A769(2006)71.See also, TH and M.Gyulassy, Nucl.Phys.A769(2006)71.

The 19The 19thth International Conference on International Conference on Ultra-Relativistic Nucleus-Nucleus CollisionsUltra-Relativistic Nucleus-Nucleus Collisions

OutlineOutline

• Introduction: Three stages of bulk dynamics• Two possible hydro initial conditions

– (Conventional) Glauber-type (as a reference)– Color Glass Condensate

• Highlights from Glauber-type initial conditions• Elliptic flow from CGC initial conditions• Comparison of eccentricity • v2 in Cu+Cu collisions• Prediction at the LHC energy• Summary and outlook

Three Stages of Bulk DynamicsThree Stages of Bulk DynamicsFinal stage:• Hadronic transportHadronic cascade model, JAM

Initial stage:• Perfect fluidity of the QGPIdeal 3D hydro

Before Collisions:• Nuclear wave function Color Glass Condensate

0z

t

Detailed description of the CGC, QGP, and hadrons in a unified wayImportance for quantitative analyses of hard probe, J/etc.

•Thermalization…

Initial Conditions in Hydro

•Unintegrated gluon distributiona.la. Kharzeev, Levin, and Nardi•Gluon production via kT factorization formula •Count deposited energy in dV at (0,x,y,s), 0 = 0.6fm/c

[Reference Initial Condition]Transverse profile: Entropy density

Longitudinal Profile:Brodsky-Gunion-Kuhn triangle

Color Glass CondensateGlauber-BGK type

sx(fm) s

x(fm)

ene.

dens

ity

ene.

dens

ity

Two Hydro Initial Conditions Which Two Hydro Initial Conditions Which Clear the “First Hurdle” Clear the “First Hurdle”

1. CGC model Matching I.C. via e(x,y,) 2.Glauber model (as a reference) Npart:Ncoll = 85%:15%

Centrality dependence Rapidity dependence

Kharzeev,Levin, and NardiImplemented in hydro by TH and Nara

Highlights from Highlights from GlauberGlauber + QGP Fluid + QGP Fluid + Hadron Gas Model + Hadron Gas Model

TH et al.(’06); in preparation.

Good agreement for bulk (pT<~1.5GeV/c) What happens to the CGC case?

20-30%

vv22(N(Npartpart) from ) from CGCCGC + QGP Fluid + QGP Fluid

+ Hadronic Gas Model+ Hadronic Gas Model

Glauber: Early thermalization Discovery of Perfect Fluid QGPCGC: No perfect fluid? Additional viscosity

required in QGP

Important to understand initial conditions much better for making a conclusion

TH et al.(’06)

Adil, Gyulassy, Hirano(’06)

Large Eccentricity from CGC Initial Large Eccentricity from CGC Initial ConditionCondition

xx

yy

Pocket formula (ideal hydro): v2 ~ 0.2 @ RHICOllitrault(’92)

Hirano and Nara(’04), Hirano et al.(’06)Kuhlman et al.(’06), Drescher et al.(’06)

System Size Dependence of v2

(Eccentricity as an input)

(Ell

ipti

c fl

ow a

s an

out

put)

Response of the system depends on its size. Inconsistent with PHOBOS data ?

PHOBOS, nucl-ex/0610037

vv22(() @ LHC and v) @ LHC and v22(sqrt(s(sqrt(sNNNN))))

•Total v2 generated mainlyin the QGP phase

•v2 monotonically increases in the hybrid model. •Hadronic dissipation washes out a bump seen at low energies.

Teaney et al.(’02)

Summary and OutlookSummary and Outlook• Dynamical modeling of bulk matter

– Entropy production from CGC collisions– Evolution of perfect fluid QGP– Evolution of dissipative hadronic gas

• Importance of bulk for other observables.• v2 overshot due to large eccentricity in CGC

– Need viscosity in the QGP?

• Much more studies needed for initial states– Universal scaling from CGC? Fluctuation?

– Pre-thermalization stage? Instability? Isotropization?

Lappi and Venugopalan(’06)Drescher and Nara(’06)

Muronga, Rischke,Teaney, Heinz, Chaudhuri,Song, Baier, Romatschke, Wiedemann…

Mrowczynski, Arnold, Moore, Yaffe, Dumitru, Nara,Rebhan, Romatschke, Strikland, Venugopalan,…

Eccentricity from Universal Saturation Scale

Almost no difference btw. conventional and universal definition for Qs^2•Conventional saturation scale

•Universal saturation scalenear the origin

dN/ddN/d and v and v22 in Cu+Cu Collisions in Cu+Cu CollisionsPseudorapidity distribution v2() for charged hadrons

v2(pT) and v2(eta) from CGC initial conditions

vv22(model) > v(model) > v22(data)(data)

20-30%

Sensitivity of Different Assumptions Sensitivity of Different Assumptions in Early/Late Stagesin Early/Late Stages

??Gradual

freezeout(Hadronic rescattering)

?Discovery of

“Perfect Liquid”Sudden

freezeout

Color Glass Condensate

Glauber-typeInitialInitialConditionCondition

FreezeoutFreezeout

Sensitivity of Different Assumptions Sensitivity of Different Assumptions in Early/Late Stages in Early/Late Stages

?Discovery of Perfect fluid QGP & hadronic

corona

Gradual

freezeoutHadronic rescattering

?Discovery of

“Perfect Liquid”Sudden

freezeout

Color Glass Condensate

Glauber-typeInitialInitialConditionCondition

FreezeoutFreezeout

Consistency?Consistency?Elliptic flow Particle ratio

Issue: Conventional ideal hydro could not reproduce particle ratio.Solution: Introduction of chemical freezeout in hydro.

Interpretation: Accidental reproduction by ideal hydro. Necessity of dissipation in the hadron phase.

TH and M.Gyulassy(’06)

N.Arbex et al.(’01), TH and K.Tsuda(’02), D.Teaney(’02)

Hyd

ro:

P.H

uovi

nen

Dat

a: P

HE

NIX

PH

EN

IX w

hite paper

Consistency again!Consistency again!Elliptic flow Color Glass Condensate

Issue: CGC initial conditions were not implemented in hydro.Solution: Introduction of CGC initial conditions in hydro.

Interpretation: Larger eccentricity from CGC Necessity of dissipation even in the QGP phase!

TH and Y.Nara(’04)

Hyd

ro:

P.H

uovi

nen

Dat

a: P

HE

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Results: K

harzeev and Levin(’01)D

ata: PH

OB

OS

Hirano,Heinz,Kharzeev,Lacey,Nara, PLB636(’06)299.

How Do Partons Get Longitudinal Momentum in Comoving System?Free Streaming eta=yFree Streaming eta=y

dN/dydN/dy

y

dN/dydN/dy

y

Sum of delta functionSum of delta function Width Width “Thermal” fluctuation“Thermal” fluctuation

Sheet:Sheet:eta=consteta=const