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Hydro Model: Past and Next Decades

Hydro Model: Past and Next Decades. Tetsufumi Hirano Dept. of Phys., Grad. School of Sci. the Univ. of Tokyo. The 13 th Heavy Ion Café, 11/14/2009. Outline. Introduction Past decade Current status Next decade (?) Apology: Discussion mainly on studies by our groups. Why Hydro?.

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Hydro Model: Past and Next Decades

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  1. Hydro Model: Past and Next Decades Tetsufumi Hirano Dept. of Phys., Grad. School of Sci. the Univ. of Tokyo The 13th Heavy Ion Café, 11/14/2009

  2. Outline • Introduction • Past decade • Current status • Next decade (?) • Apology: Discussion mainly on studies by our groups

  3. Why Hydro? • Static • EoS from Lattice QCD • Finite T, m field theory • Critical phenomena • Chiral property of hadron • Dynamic Phenomena in HIC • Expansion, Flow • Space-time evolution of • thermodynamic variables

  4. A Remark Hydrodynamic Model ≠Hydrodynamics

  5. Hydro Status (~ 1995) • Extensively analyzing data • Marburg: Cartesian, cylindrical sym. • Finland: Cartesian, cylindrical sym. • Waseda: tau-eta, cylindrical sym. • Codes exist • Frankfurt: (3+1)D Cartesian • Saclay: (2+1)D, Bjorken scaling • Bergen: (3+1)D, Cartesian • …

  6. Status in Waseda Group in 1995 • 3D ideal hydro code with a cylindrical symmetry existed. • Code (Akase et al.) • Finite baryon density (Ishii & Muroya) • Quantum Langevin eq. as a bridge btw. the 1st principle and phenomenology (Mizutani, Muroya, Namiki) QCD  Dispersion relation  EoS & transport coeff.  Hydro

  7. My Thesis (B.S. & M.S.) Thermal Photon Thermal Dileption TH et al.(PTP supp.,’97) TH et al.(PTP,’97)

  8. EM Radiation from Off-Shell Source • Creation/Annihilation • operator of quasi-particle • described using quantum • Langevin eq. • No threshold in • pi+pi- e+e- • in medium. •  Enhancement around • M~2mpi TH et al.(PTP,’97)

  9. Hiroshima School & QM’97 • Lots of criticism on our hydro model • EoS (resonances? Zero baryon density@SPS?) • Relation with QCD • Many parameters… • How much is our conclusion robust? • Recognize the importance of a sophisticated hydro simulation • Elliptic flow was measured at SPS for the first time by Tsukuba group (WA98). • 3D (or at least no cylindrical symmetry) hydro was demanded. • Make up my mind to write a code from a scratch

  10. Poor man’s Idea/Strategy • Less uncertainties • No geometrical symmetry, no simplified assumption (Neither cylindrical nor Bjorken solution) • Robust algorithm (PPM) • More known physics • More resonances in the hadron phase • Initial condition taking into account thickness of colliding nuclei • Thanks to rapid evolution of computing resources

  11. Full 3D Hydro in Cartesian Coordinate • First realistic application of • full 3D hydro to HIC at SPS • No geometrical symmetry • No Bjorken scaling • (Except for initial long. flow) • EoS with resonances • up to 2 GeV (from Nonaka) • Initial cond.  Thickness •  Automatic at finite b TH (PRL,’01) Reduction of v2 due to contribution from decays

  12. Jacobian Singularity TH (PRL,’01) E.g.) rhopipi Dilution due to decay kinematics

  13. Full 3D Hydro Available at

  14. First Study of Full 3D in tau-eta • Full 3D hydro in • relativistic tau-eta • coordinate •  Perfect fluid (or • early thermalization) • only near eta ~ 0? • “Elliptic flow puzzle” • Initial condition? • Incomplete • thermalization? TH(PRC,’01)

  15. Extension of Parameter Space • Single Tf in hydro • Hydro works? • Both ratio and • spectra? mi

  16. Chemical Potential & EoS Partial chemical equilibrium (PCE) Example of chem. potential TH and K.Tsuda(PRC,’02)

  17. Does Dynamics Change?  Yes T(t) at origin Model CE Model PCE <vr>(Tth)

  18. pT spectra • How to fix Tth in conventional • hydro • Response to pT slope • Spectrum harder with • decreasing Tth • Up to how large pT? CE PCE • Tth independence of slope in • chemically frozen hydro • No way to fix Tth • Suggests necessity of • (semi)hard components TH and K.Tsuda(PRC,’02)

  19. Elliptic Flow Partial Chemical Equilibrium Chemical Equilibrium If we knew Tf, we were able to see whether hydro works. Although paper was not intend to claim positive conclusion, … The issue will be revisited again. p K p TH and K.Tsuda(PRC,’02)

  20. TH and M.Gyulassy(’05) Mean pT is the Key pdV work + (number) /(entropy) t t Slope of v2(pT) ~ v2/<pT> Response todecreasing Tth (or increasing t) t

  21. dE/dy and n/s Simplest case: Pion gas Longitudinal expansion  pdV work! • CFO: dS/dy = const. • dN/dy = const. • <pT> decreases CE: dS/dy = const. • dN/dy decreases (mass effect) • <pT> can increase as long as <ET>dN/dy decreases. dET/dy should decrease with decreasing Tth.  <ET>dN/dy should so.

  22. Hydro, Not the Same Hydro+Cascade won… PHENIX white paper (’05)

  23. Hydro at Work =? Deconfinement Rapid increase of entropy density  Hydro at work  Evidence of QGP(?) TH and M.Gyulassy(’05)

  24. Hydro + Cascade in Full 3D QGP fluid+hadron gas QGP+hadron fluids QGP only Suppression in forward and backward rapidity TH et al.,(’05)

  25. Mass Splitting = Hadronic effects Pion 20-30% Proton Mass ordering comes from hadronic rescattering effect. Interplay btw. radial and elliptic flows. Mass dependence is o.k. from hydro+cascade. When mass splitting appears? TH et al.,(’08)

  26. CGC Initial Condition Three parameters are enough (!?) Partly resolve a weak point of hydro model. “From soup to nuts” by W. Zaic TH and Y.Nara,(’04)

  27. CGC Eccentricity CGC or Perfect fluidity, compatible? TH et al.,(’06)

  28. Hydro Model: Current Status

  29. … 20-30% 10-20% 0-10% Current Status of Dynamical Modeling hadron gas • Initial condition • Model* • MC-Glauber • MC-KLN (CGC) • Participant eccentricity • Centrality cut time QGP fluid collision axis 0 Au Au *H.J.Drescher and Y.Nara (2007)

  30. Current Status of Dynamical Modeling hadron gas • Ideal Hydrodynamics* • Initial time 0.6fm/c • Model EoS • lattice-based# • 1st order time QGP fluid collision axis 0 Au Au *T.Hirano(2002), #Lattice part : M.Cheng et al. (2008)

  31. Current Status of Dynamical Modeling hadron gas • Hadronic afterburner • Hadronic transport • model, JAM* • Switching temperature • T=160 MeV • Note: We changed switching • temperature from 169 MeV to • 160 MeV to utilize lattice-based • EoS which matches smoothly to • a resonance gas model at this • temperature. time QGP fluid collision axis 0 Au Au *Y.Nara et al., (2000)

  32. Current Status: pT distribution Hybrid model works well up to pT~1.5 GeV/c (1st order, dotted) and 2-3 GeV/c (lattice-based, solid)

  33. Current Status: Elliptic Flow Au+Au Cu+Cu • Soft EoS might have mimicked viscosity. • Highly sensitive to initial models. • Perfect fluid and CGC, compatible? •  Need more studies on initial condition and viscosity

  34. Current Status: Differential Elliptic Flow Au+Au 200 GeV • Glauber+ lattice(-motivated) EoS • Eccentricity fluctuation is essential • in central collisions. • Centrality dependence  OK • Viscosity would be needed for • better description. • Eager to see PID v2 data with less • errors and less non-flow effects • in low pT (<2 GeV/c) region.

  35. Summary for Current Status • Initial conditions (Glauber/CGC) + ideal hydro (lattice-based EoS/1st order EoS) + hadronic afterbuner (JAM) • Within the Glauber type initial conditions, the strong 1st order phase transition is unlikely to be realized. Note: Shear viscosity generally reduces v2. • The most ambiguous module  Initial condition (entropy distribution, initial time, initial flow, …).  Much more studies on the pre-thermalization stage

  36. v2 from ideal hydro point of view • 1992 • Proposal of “anisotropic transverse flow” (Ollitrault) • 2000 • Prediction of v2(cent) and v2(pT) @ y=0 (Heinz, Kolb, Huovinen) • 2001 • v2(pT), v2(cent) (STAR) • v2(eta) (Hirano) • Hydro+cascade in 2D (Teaney) • 2002 • v2(pT), v2(cent) (PHENIX); v2(eta) (PHOBOS) • Chemical freezeout (Hirano, Teaney) • 2005 • Press release of perfect fluidity (BNL) • Importance of hadronic dissipation (Hirano, Gyulassy) • 2006 • Hydro + cascade in 3D; v2(eta); CGC eccentricity (Hirano, Nara, Heinz) • Eccentricity fluctuation (Brazil group)

  37. Hydro Model: Next Decade

  38. Future Perspectives • Viscosity (shear & bulk)  Important to extract transport coefficients from data  Is viscous hydrodynamic equation not settled yet? • Event-by-event fluctuation  Perhaps, important to understand soft ridge structure  Fluctuation and correlation in the longitudinal direction  Is hydrodynamics really applicable? • Chemical equilibration  How do (anti-)quark degrees appear?  Schwinger mechanism? Sequential equilibration? • More realistic pre-thermalization stage  A last piece of heavy ion collision jigsaw-puzzle

  39. Lots of Terms… Similar for other dissipative currents Quite similar forms to TKO eqs. A.Monnai and TH (in preparation)

  40. QGP Fluid as a Playground of Hot QCD Success of hydro (Reasonable agreement btw. data and hydro) Starting point of finite temperature QCD by means of high energy heavy ion collisions Ex.) 1. Melting temerature of chamonia 2. Stopping power of QGP QGP fluid as a heat bath Study of hot QCD medium

  41. Hydro + Jet Model Utilization of 3D hydro outputs for jet quenching Naturally fill the gap btw. data and hydro in high pT. TH and Y.Nara(PRC,’02)

  42. First Study on Di-jet E-loss along eikonal path is not sufficient. Broadening in QGP also reduce the away-side peak. TH and Y.Nara (PRL,’03)

  43. Interplay btw Soft and Hard Mass dependence of radial flow effects  Push to high pT E-loss  Shift to low pT Now interpreted as meson/baryon effects rather than mass effects. TH and Y.Nara (PRC,’04)

  44. Tricky BRAHMS Data • Thanks to full 3D calculation •   Almost no rapidity • dependence below eta<2. • Just kinematic effect • leads to RAA < 1 • CGC? • Prediction of high pT v2 • in forward rapidity

  45. Constraint of Melting Temperature Best fit @ (TJ/y, Tc, fFD) = (2.00Tc, 1.34Tc, 10%) • Onset of J/psi suppression at Npart ~ 160 • TJ/ycan be determined in a narrow region. T.Gunji et al.(’07)

  46. Global Fitting of RAA and IAA K=4.1  Best fit N.Armesto et al.(’09)

  47. Statistical Analysis “K-factor” 4.1 ± 0.6 (standard setting) Re-thinking about energy loss formula needed? N.Armesto et al.(’09)

  48. Observational QGP Physics Making a transition from discovery stage to precision science “Observational” QGP Physics Observational Cosmology “Best” cosmological parameters C.L.Bennett et al.,Ap.J.Suppl(’03) CMB from WMAP

  49. Dynamical Modeling at LHC? • Hard/rare probes are certainly important at LHC. • If one wants to constrain medium parameters, a precise description of bulk dynamics is demanded. • Moderate case: Extrapolation of RHIC physics • Dynamical models should urgently reflect lessons at RHIC. • Extrapolating parameters in the model, one predicts observables at LHC. • Extreme case: Plenty of “exotics” • We need a lot of ideas of what happens at LHC. • Then, materialize them in the dynamical model.

  50. Prediction at the LHC Energy Elliptic flow coefficient Extrapolation from RHIC to LHC TH et al.(’07)

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