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CGC, Full 3D Hydro, and Hadronic Cascade

The 19 th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions. CGC, Full 3D Hydro, and Hadronic Cascade. Tetsufumi Hirano Department of Physics, University of Tokyo. TH, U.Heinz, D.Kharzeev, R.Lacey, and Y.Nara, Phys.Lett.B636(2006)299,

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CGC, Full 3D Hydro, and Hadronic Cascade

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  1. The 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions CGC, Full 3D Hydro, and Hadronic Cascade Tetsufumi Hirano Department of Physics, University of Tokyo TH, U.Heinz, D.Kharzeev, R.Lacey, and Y.Nara, Phys.Lett.B636(2006)299, See also, TH and M.Gyulassy, Nucl.Phys.A769(2006)71.

  2. Outline • 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

  3. Three Stages of Bulk Dynamics • Final stage: • Hadronic transport • Hadronic cascade model, JAM t • Initial stage: • Perfect fluidity of the QGP • Ideal 3D hydro • Thermalization… z • Before Collisions: • Nuclear wave function •  Color Glass Condensate 0 Detailed description of the CGC, QGP, and hadrons in a unified way Importance for quantitative analyses of hard probe, J/Y, etc.

  4. Initial Conditions in Hydro Glauber-BGK type Color Glass Condensate [Reference Initial Condition] Transverse profile: Entropy density Longitudinal Profile: Brodsky-Gunion-Kuhn triangle • Unintegrated gluon distribution • a.la. Kharzeev, Levin, and Nardi • Gluon production via kT • factorization formula • Count deposited energy in dV at • (t0,x,y,hs), t0 = 0.6fm/c ene.density ene.density x(fm) x(fm) hs hs

  5. Two Hydro Initial Conditions Which Clear the “First Hurdle” Centrality dependence Rapidity dependence Kharzeev,Levin, and Nardi Implemented in hydro by TH and Nara 1. CGC model Matching I.C. via e(x,y,h) 2.Glauber model (as a reference) Npart:Ncoll = 85%:15%

  6. TH et al.(’06); in preparation. Highlights from Glauber + QGP Fluid + Hadron Gas Model 20-30% Good agreement for bulk (pT<~1.5GeV/c)  What happens to the CGC case?

  7. v2(Npart) from CGC + QGP Fluid + Hadronic Gas Model TH et al.(’06) • Glauber: • Early thermalization • Discovery of Perfect Fluid QGP • CGC: • No perfect fluid? • Additional viscosity • required in QGP Important to understand initial conditions much better for making a conclusion Adil, Gyulassy, Hirano(’06)

  8. Large Eccentricity from CGC Initial Condition y x Hirano and Nara(’04), Hirano et al.(’06) Kuhlman et al.(’06), Drescher et al.(’06) Pocket formula (ideal hydro): v2 ~ 0.2e @ RHIC Ollitrault(’92)

  9. System Size Dependence of v2 (Elliptic flow as an output) PHOBOS, nucl-ex/0610037 (Eccentricity as an input) Response of the system depends on its size.  Inconsistent with PHOBOS data ?

  10. v2(h) @ LHC and v2(sqrt(sNN)) • v2 monotonically increases in the hybrid model. • Hadronic dissipation washes out a bump seen at low energies. • Total v2 generated mainly • in the QGP phase Teaney et al.(’02)

  11. Summary 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? Muronga, Rischke,Teaney, Heinz, Chaudhuri, Song, Baier, Romatschke, Wiedemann… Lappi and Venugopalan(’06) Drescher and Nara(’06) Mrowczynski, Arnold, Moore, Yaffe, Dumitru, Nara, Rebhan, Romatschke, Strikland, Venugopalan,…

  12. Eccentricity from Universal Saturation Scale Almost no difference btw. conventional and universal definition for Qs^2 • Conventional saturation scale • Universal saturation scale near the origin 

  13. dN/dh and v2 in Cu+Cu Collisions v2(h) for charged hadrons Pseudorapidity distribution

  14. v2(pT) and v2(eta) from CGC initial conditions 20-30% v2(model) > v2(data)

  15. Sensitivity of Different Assumptions in Early/Late Stages Initial Condition Glauber-type Color Glass Condensate Freezeout Sudden freezeout Discovery of “Perfect Liquid” ? Gradual freezeout (Hadronic rescattering) ? ?

  16. Sensitivity of Different Assumptions in Early/Late Stages Initial Condition Glauber-type Color Glass Condensate Freezeout Sudden freezeout Discovery of “Perfect Liquid” ? Gradual freezeout Hadronic rescattering Discovery of Perfect fluid QGP & hadronic corona ?

  17. Consistency? Elliptic flow Particle ratio Hydro: P.Huovinen Data: PHENIX PHENIX white paper 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. N.Arbex et al.(’01), TH and K.Tsuda(’02), D.Teaney(’02) TH and M.Gyulassy(’06)

  18. Consistency again! Elliptic flow Color Glass Condensate Hydro: P.Huovinen Data: PHENIX Results: Kharzeev and Levin(’01) Data: PHOBOS 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) Hirano,Heinz,Kharzeev,Lacey,Nara, PLB636(’06)299.

  19. How Do Partons Get Longitudinal Momentum in Comoving System? Free Streaming eta=y Sheet: eta=const dN/dy dN/dy Width “Thermal” fluctuation Sum of delta function y y

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