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Hadronic Rescattering Effects after Hadronization of QGP Fluids

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

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Hadronic Rescattering Effects after Hadronization of QGP Fluids

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

  2. Two Topics • 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 • T.Hirano,M.Isse,A.Ohnishi,Y.Nara,K.Yoshino, (in preparation).

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

  4. TH&Gyulassy(’06),TH,Heinz,Kharzeev,Lacey,Nara(’06) Hydro Meets Data for the First Time at RHIC: “Current” Three Pillars • Perfect Fluid (s)QGP Core • Ideal hydro description of the QGP phase • Necessary to gain integrated v2 • Dissipative Hadronic Corona • Boltzmann description of the hadron phase • Necessary to gain enough radial flow • Necessary to fix particle ratio dynamically • Glauber Type Initial Condition • Diffuseness of initial geometry A Lack of each pillar leads to discrepancy!

  5. (1) Glauber and (2) CGC Hydro Initial Conditions Which Clear the First Hurdle Centrality dependence Rapidity dependence • Glauber model • Npart:Ncoll = 85%:15% • CGC model • Matching I.C. via e(x,y,h)

  6. pT Spectra for identified hadronsfrom QGP Hydro+Hadronic Cascade dN/dy and dN/dpT are o.k. by hydro+cascade. Caveat: Other components such as recombination and fragmentation should appear in the intermediate-high pT regions.

  7. TH et al.(’06) v2(Npart) from QGP Hydro + Hadronic Cascade • Glauber: • Early thermalization • Mechanism? • CGC: • No perfect fluid? • Additional viscosity • is required in QGP Result of JAM: Courtesy of M.Isse Importance of better understanding of initial condition

  8. Talk by Y.Nara in “Interaction btw hard probes and the bulk”. Large Eccentricity from CGC Initial Condition Hirano and Nara(’04), Hirano et al.(’06) Kuhlman et al.(’06), Drescher et al.(’06) y x Pocket formula (ideal hydro): v2 ~ 0.2e @ RHIC energies Ollitrault(’92)

  9. v2(pT) for identified hadronsfrom QGP Hydro + Hadronic Cascade Glauber type initial condition CGC initial condition 20-30% 20-30% Mass dependence is o.k. v2(model) > v2(data)

  10. Summary So Far • 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?

  11. How Large Hadronic Rescattering? • Hybrid Model: QGP Fluid + Hadronic Gas + Glauber I.C. • 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 phase • Particle ratio fixed at Tch • Chemical equilibrium changes dynamics. TH and K.Tsuda(’02),TH and M.Gyulassy(’06)

  12. Hydro ~ Hydro+Cascade for Protons • Tth ~ 100 MeV • Shape of spectrum • changes due to • radial flow rather • than hadronic • dissipation for • protons. radial flow

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

  14. Hadronic Dissipation Suppresses Differential Elliptic Flow Difference comes from dissipation only in the hadron phase • Relevant parameter: Gs/t • Teaney(’03) • Dissipative effect is not so • large due to small expansion • rate (1/tau ~ 0.05-0.1 fm-1) Caveat: Chemically frozen hadronic fluid is essential in differential elliptic flow. (TH and M.Gyulassy (’06))

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

  16. v2(h) fromQGP Hydro + Hadronic Cascade Suppression due to hadronic dissipation

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

  18. Summary of the 1st Topic • 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. • 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.

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

  20. http://nt1.c.u-tokyo.ac.jp/~hirano /parevo/parevo.html T.Hirano, talk at “Interaction between hard probes and the bulk” (tomorrow)

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

  22. pT distributions GLV 1st order (simplified) formula 20-30% centrality Effective parton density from hydro Fitting the pT data is our starting point. Independent fragmentation C=2.5-3.0 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

  23. v2 @ intermediate-high pT p 20-30% centrality v2(JFS) ~ 0.1 at b~8 fm without assuming an unrealistic hard sphere

  24. High pT v2 puzzle!? STAR, PRL93,252301(’04)

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

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

  27. Summary of the 2nd 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.

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

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