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**Dynamic Modeling for Relativistic Heavy Ion Collisions**

Huichao Song Peking University CPOD2014, Bielefeld, Germany, Nov.17-Nov.21, 2014 11/20/2014

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**QGP-the most perfect fluid in the world?**

BNL News, 2005 How perfect is the QGP fluid?

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**What is viscosity Assume: (RHIC&LHC)**

Shear viscosity – measures the resistance to flow act against the buildup of flow anisotropy Bulk viscosity – measures the resistance to expansion act against the buildup of radial flow Heat conductivity – measures the ability of heat transfer Assume: (RHIC&LHC)

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**Hydrodynamics & its Hybrid Model**

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**Viscous Hydrodynamics**

Evolution equations for shear pressure tensor and bulk pressure Assume zero net baryon density & heat conductivity at RHIC and the LHC Song & Heinz PLB08, PRC08 2+1-d: OSU, INT, Stony Brook, Pudue, Calcutta (2008), Crakow, Frankfurt(2010) … … 3+1-d: Mcgill(2011), MSU(2012), Crakow(2012), Nagoya(2013)… …

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**Viscous Hydro + Hadron Cascade Hybrid Model**

QGP HRG Initial conditions viscous hydro hadron cascade viscous hydro (QGP) + URQMD (HRG) viscous hydro (QGP & HRG) ideal hydro (QGP & HRG) H. Song, S. Bass, U. Heinz, PRC2011

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**Event-by-event hydrodynamics**

Single shot simulations: smoothed initial conditions (before 2010) E-b-E simulations: fluctuating initial conditions (since 2010) B. Schenke et al, Phys.Rev. C85, (2012)

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**Extracting QGP viscosity from elliptic flow data – VISHNU results**

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**VISHNU hybrid model & QGP viscosity**

H. Song,et.al, PRL2011 MC-KLN MC-Glauber -Main uncertainties come from initial conditions -Other uncertainties (much smaller) -Initial flow, bulk viscosity, single shot vs. e-b-e calculations (each of them shift V2 by a few percent, partial cancellation among them)

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V2 at RHIC and LHC Song, Bass & Heinz, PRC 2011 The average QGP viscosity is roughly the same at RHIC and LHC

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**LHC: spectra for identified hadrons**

Song, Bass & Heinz,PRC 2014 -a nice fit of spectra for pions, kaons and proton

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**Spectra of Strange & Multi-strange Hadrons**

X.R. Zhu, H. Song et al., in preparation -a nice fit of spectra for Lambda, Xi, and Omega

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**for pions, kaons & protons at LHC**

VISHNU Song, Bass & Heinz,PRC 2014 A very nice fit of V2(PT) for all centrality bins at LHC from VISHNU hybrid model

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**v2 of Strange & Multi-strange Hadrons**

X.R. Zhu, H. Song et al., in preparation -Nice descriptions of Lambda, Xi and Omega V2 at various centralities

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**Initial State Fluctuations, Final State Correlations **

& the QGP viscosity

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**Uncertainties from Initial Conditions**

H. Song, S. Bass, U. Heinz, T. Hirano, and C. Shen, PRL2011 MC-KLN MC-Glauber Main uncertainties come from initial conditions MC-KLN, larger HIGHER value of QGP viscosity MC-Glauber, smaller LOWER value of QGP viscosity

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**MC-KLN & MC-Glauber initializations & V3**

Pure viscous hydro simulations : Qiu, Shen & Heinz, PLB2012 V3 prefer lower value of QGP viscosity

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**Initialization & Pre-equilibrium: Updates after 2011**

-fluctuations of nucleon positions: MC-Glauber, MC-KLN -fluctuations of color charges (in the framework of CGC): IP-Glasma: B. Schenke et al., arXiv: ; [nucl-th] Correlated Fluctuation: B. Muller & A. Schafer, arXiv: [hep-ph] . -fluctuations of local gluon numbers (in the famework of MC-KLN): Multiplicity fluctuations: A. Dumitru and Y. Nara, Phys. Rev. C 85, (2012) -Pre-equilibriums: URQMD initialization: H.Petersen & M. Bleicher, Phys. Rev. C81, ,2010 AMPT initialization: L. Pang, Q.Wang & X.Wang, arXiv: [nucl-th] EPOS/NEXUS initialization: K. Werner et al., Phys. Rev. C83:044915,2011 … … … … Mostly, the effects of initializations /pre-equilibrium dynamics was studied with ideal hydro. Their quantitative influences on are still unknown.

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**Flow at RHIC & LHC: results from IP-Glasma + MUSIC**

Gale, Jeon ,Schenke, Tribedy &Venugopalan PRL2013

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**New Observables for Higher Order Flow Harmonics**

Luzum & Ollitrault, Qiu & Heinz,12-08 C. Gale et al. 12-09 -They are all sensitive to the QGP viscosity will constrain initialization models, tightening the limit on -A further study of flow data in different aspects, using e-b-e hybrid model

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**Massive Data evaluation**

Exp Observables Theoretical Inputs: particle yields spectra - elliptic flow - triangular flow & higher order flow harmonics - event by event Vn distributions higher-order event plane correlations … … … - type of initial conditions initial flow - starting time EoS shear viscosity - bulk viscosity - relaxation times - freeze-out/switching cond. … … … …

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**Massive data evaluation**

Early CHIMERA Results (Comprehensive Heavy Ion Model Evaluation and Reporting Algorithm) Spectra spectra elliptic flow HBT R. Soltz, et al., PRC2013 Please also refer to the work from MSU-DUKE collaboration, arXiv:

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**Massive data evaluation**

Bernhard & Bass, JET collaboration

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**Bulk Viscosity Long , but not full lists of articles:**

J.Noronha-Hostler, J.Noronha and F.Grassi, arXiv: [nucl-th] M. Habich and P. Romatschke, arXiv: [hep-ph]. J.Noronha-Hostler, et.al., Phys.Rev. C 88, (2013) K.Dusling and T.Schäfer, Phys.Rev.C 85, (2012) P. Bozek, Phys. Rev. C81, (2010) H.Song and U.WHeinz, Phys. Rev. C81, (2010) G.Torrieri et al. Phys.Rev. C78, (2008). K. Rajagopal et al. JHEP 1003, 018(2008) . A. Monnai et al. Phys.Rev. C (2009) R.Fries et al. Phys.Rev. C (2008) . … … … … … …

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**The interplay between shear and bulk viscosity**

Visc. suppression of elliptic flow shear visc. shear+ bulk visc. ideal Song & Heinz PRC09 QGP HRG Min. AdS/CFT prediction -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 Introduction 25

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**Ultracentral Collisions: bulk visc. & NN correlations**

Shen, Qiu and Heinz 2013 G. Denicol, QM2014 -MC-Glauber & MC-KLN: can not simultaneously fit V2 and V3 -IP+Glasma + NN correlations + bulk viscosity nicely reproduces Vn in ultra-central collisions

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**Soft Particle Yields, Chemical & thermal Freeze-out at the LHC**

J. Stachel,SQM 2013 Tch = 165MeV Tch = 150MeV v.s.

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**dN/dy for identified hadrons (RHIC & LHC)**

Song, Bass & Heinz,PRC 2014 RHIC : 200 A GeV Au+Au LHC : 2.76 A TeV Pb+Pb -VISHNU nicely describes the multiplicity for pions, kaons & protons -B-Bbar annihilations plays an important role for a nice fit of the proton data VISHNU : Tsw= 165MeV Please also refer to F. Becattini et al., PRC2012

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**dN/dy for identified hadrons (LHC)**

X.R. Zhu, H. Song et al., in preparation -VISHNU nicely describes the multiplicity for various hadrons at the LHC

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**dN/dy for identified hadrons (LHC)**

X.R. Zhu, H. Song et al., in preparation VISHNU most central collisions

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**Statistical Model vs. VISHNU**

Statistical Model : Tch ~ 150 MeV VISHNU : Tsw= 165MeV - Statistical Model: Tch is extracted from final hadron yields; averaged chemical freeze-out temperature for final stable hadrons - VISHNU: Tsw corresponds QGP chemical freeze-out; different hadrons may have different chemical freeze-out temperature.

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**Chemical freeze-out for various hadrons in UrQMD**

X.R. Zhu, H. Song et al., in preparation

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**Thermal freeze-out for various hadrons in UrQMD**

X.R. Zhu, H. Song et al., in preparation -earlier freeze-out for Xi and Omega!

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phi-meson

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**Elliptic flow for phi at the LHC**

Song, Bass & Heinz, PRC 2014 200A GeV Au+Au -Hadron cascade: small cross sections for phi -mass ordering between phi and proton are independent of collision energies, centralities & theoretical details T. Hirano 3+1-d ideal hydro+JAM

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**Elliptic flow for phi at the LHC**

Song, Bass & Heinz, PRC 2014 ALICE 2014

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**Elliptic flow for phi at the LHC**

Song, Bass & Heinz, PRC 2014 STAR Preliminary ALICE 2014

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**phi V2 in strong & weakly coupling limit**

Song, Bass & Heinz, PRC 2014 -hydro + Tdec =165 MeV weakly coupling limit -hydro + Tdec =100 MeV strong coupling limit -VISHNU: small cross sections for phi

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**phi V2 in strong & weakly coupling limit**

Song, Bass & Heinz, PRC 2014 -hydro + Tdec =165 MeV weakly coupling limit -hydro + Tdec =100 MeV strong coupling limit VISHNU: small cross sections for phi STAR Preliminary ALICE 2014

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Summary

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**Summary -Extraction from elliptic flow data using VISHNU indicates:**

(MC-Glauber; MC-KLN) -Slightly larger averaged QGP viscosity at the LHC -Recent developments on initialization models: color charge fluctuations; multiplicity fluctuations; initial flow fluctuations … … -To implement e-b-e simulations to further study other flow will help us to constrain initialization models, tightening the limit on -New flow data: triangular flow & higher order flow harmonics, higher-order event plane correlations e-b-e vn … ... -massive data evaluation are needed -VISHNU could nicely describe the yields of various hadrons -B-Bbar annihilations is important to describe the proton yields at the LHC VISHNU: an indication of different chemical freeze-out temperature for various hadrons

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