Hadronic Rescattering Effects after Hadronization of QGP Fluids Tetsufumi Hirano Institute of Physics, University of Tokyo Workshop “Hadronization” in 2006 RHIC & AGS annual users’ meeting

Two Topics Hadronic Rescattering Effects after Hadronization of QGP fluids Hadronic Rescattering Effects after Hadronization of QGP fluids –T.Hirano, U.Heinz, D.Kharzeev, R.Lacey, Y.Nara, PLB636(2006)299; (in preparation). Hadronization through Jet-Fluid Strings Hadronization through Jet-Fluid Strings –T.Hirano,M.Isse,A.Ohnishi,Y.Nara,K.Yoshino, (in preparation).

(CGC +)QGP Hydro+Hadronic Cascade 0 z t (Option) Color Glass Condensate sQGP core (Full 3D Ideal Hydro) HadronicCorona(Cascade,JAM) c.f. Similar approach by Nonaka (talk in “perfect fluid” workshop) TH et al.(’05-) 0.6fm/c

Hydro Meets Data for the First Time at RHIC: “Current” Three Pillars 1. Perfect Fluid (s)QGP Core Ideal hydro description of the QGP phaseIdeal hydro description of the QGP phase Necessary to gain integrated v 2Necessary to gain integrated v 2 2. Dissipative Hadronic Corona Boltzmann description of the hadron phaseBoltzmann description of the hadron phase Necessary to gain enough radial flowNecessary to gain enough radial flow Necessary to fix particle ratio dynamicallyNecessary to fix particle ratio dynamically 3. Glauber Type Initial Condition Diffuseness of initial geometryDiffuseness of initial geometry TH&Gyulassy(’06),TH,Heinz,Kharzeev,Lacey,Nara(’06) A Lack of each pillar leads to discrepancy!

(1) Glauber and (2) CGC Hydro Initial Conditions Which Clear the First Hurdle Glauber modelGlauber model N part :N coll = 85%:15% N part :N coll = 85%:15% CGC modelCGC model Matching I.C. via e(x,y,  ) Matching I.C. via e(x,y,  ) Centrality dependence Rapidity dependence

p T Spectra for identified hadrons from QGP Hydro+Hadronic Cascade Caveat: Other components such as recombination and fragmentation should appear in the intermediate-high p T regions. dN/dy and dN/dp T are o.k. by hydro+cascade.

v 2 (N part ) from QGP Hydro + Hadronic Cascade Glauber: Early thermalization Early thermalization Mechanism? Mechanism? CGC: No perfect fluid? No perfect fluid? Additional viscosity Additional viscosity is required in QGP Importance of better understanding of initial condition Result of JAM: Courtesy of M.Isse TH et al.(’06)

Large Eccentricity from CGC Initial Condition x y Pocket formula (ideal hydro): v 2 ~ 0.2 RHIC energies v 2 ~ 0.2 RHIC energies Ollitrault(’92) Hirano and Nara(’04), Hirano et al.(’06) Kuhlman et al.(’06), Drescher et al.(’06) Talk by Y.Nara in “Interaction btw hard probes and the bulk”.

v 2 (p T ) for identified hadrons from QGP Hydro + Hadronic Cascade Glauber type initial condition CGC initial condition Mass dependence is o.k. v 2 (model) > v 2 (data) 20-30%

Summary So Far An answer to the question, “whether perfect fluid is discovered”, depends on relatively unknown initial conditions. An answer to the question, “whether perfect fluid is discovered”, depends on relatively unknown initial conditions. –Glauber: Early thermalization + perfect fluid QGP –CGC: No perfect fluid QGP? Discovery of EITHER a perfect fluid QGP OR the CGC + a viscous fluid QGP? Discovery of EITHER a perfect fluid QGP OR the CGC + a viscous fluid QGP?

How Large Hadronic Rescattering? Hybrid Model: Hybrid Model: QGP Fluid + Hadronic Gas + Glauber I.C. Hydro Model: Hydro Model: QGP Fluid + Hadronic Fluid + Glauber I.C. Comparison  Try to draw information on hadron gas Key technique in hydro: Partial chemical equilibrium in hadron phasePartial chemical equilibrium in hadron phase Particle ratio fixed at T chParticle ratio fixed at T ch  Chemical equilibrium changes dynamics. TH and K.Tsuda(’02),TH and M.Gyulassy(’06) TH and K.Tsuda(’02),TH and M.Gyulassy(’06)

Hydro ~ Hydro+Cascade for Protons T th ~ 100 MeVT th ~ 100 MeV Shape of spectrumShape of spectrum changes due to radial flow rather than hadronic dissipation for protons. radial flow

Opposite Behaviors for Pions Softer: Hadronic Fluid (pdV work) Harder: Hadronic Gas (Viscous pressure) Green line: Teaney(’03) Caveat: Transverse expansion Non-scaling solution

Hadronic Dissipation Suppresses Differential Elliptic Flow Difference comes from dissipation only in the hadron phase Caveat: Chemically frozen hadronic fluid is essential in differential elliptic flow. (TH and M.Gyulassy (’06)) Relevant parameter:  s Relevant parameter:  s  Teaney(’03) Teaney(’03) Dissipative effect is not soDissipative effect is not so large due to small expansion rate (1/tau ~ fm -1 )

Mass Splitting Comes from the Late Hadronic Stage Proton Pion Pion: Generation of v2 in the hadronic stage Proton: Radial flow effects Huovinen et al.(’01) Mass splitting itself is NOT a direct signature of perfect fluid QGP.

v 2 (  ) from QGP Hydro + Hadronic Cascade Suppression due to hadronic dissipation

Excitation Function of v2 Hadronic Dissipation is huge at SPS.is huge at SPS. still affects v2 at RHIC.still affects v2 at RHIC. is almost negligible at LHC.is almost negligible at LHC.

Summary of the 1 st Topic An answer to the question, “whether perfect fluid is discovered”, depends on relatively unknown initial conditions. An answer to the question, “whether perfect fluid is discovered”, depends on relatively unknown initial conditions. Protons: pT slope becomes harder due to radial flow. Protons: pT slope becomes harder due to radial flow. Pions: pT slope becomes harder due to dissipation. However, it becomes softer due to pdV work in the case of no viscosity. Pions: pT slope becomes harder due to dissipation. However, it becomes softer due to pdV work in the case of no viscosity. The effect of hadronic dissipation is large in small multiplicity as expected. The effect of hadronic dissipation is large in small multiplicity as expected.

Hadronization through Jet-Fluid Strings In Rudy Hwa’s language, this model describes shower-shower, shower-thermal, NOT thermal-thermal. shower-shower, shower-thermal, NOT thermal-thermal. T.Hirano, M.Isse, Y.Nara, A.Ohnishi, K.Yoshino, (in preparation). Space-time evolution of the QGP fluid  Open data table StringFragmentation  PYTHIA (Lund) Energy loss  GLV 1 st order

/parevo/parevo.html T.Hirano, talk at “Interaction between hard probes and the bulk” (tomorrow)

Comparison btw two mechanisms Lorentz-boosted thermal parton distribution at T=T c hyper surface from hydro simulations

p T distributions 20-30% centrality GLV 1 st order (simplified) formula Effective parton density from hydro Independent fragmentation C= Jet-fluid string C=8.0 Fluctuation of the number of emitted gluon Chemical non-equilibrium in the QGP phase Higher order in opacity expansion Cronin effect … Neglecting many effects Fitting the p T data is our starting point.

v intermediate-high p T v 2 (JFS) ~ 0.1 at b~8 fm without assuming an unrealistic hard sphere 20-30% centrality 

High p T v 2 puzzle!? STAR, PRL93,252301(’04)

Mechanism 1 In order to compensate this effect, one needs additional parton energy loss in comparison with independent fragmentation scheme. This enhances v2. Additional push!

Mechanism 2 Direction of flow ~Perpendicular to surface Direction of jets ~Radial on average Direction of string momentum is tilted to reaction plane in comparison with collinear direction.

Summary of the 2 nd topic Hadronization through jet-fluid strings –Realistic space-time evolution of thermalized partons is considered through hydrodynamic simulations. (Data table is now available on the web!) – v2 is enhanced in intermediate-high pT regions.

Source Function from 3D Hydro + Cascade Blink: Ideal Hydro, Kolb and Heinz (2003) Caveat: No resonance decays in ideal hydro How much the source function differs from ideal hydro in Configuration space?