1. Hadronic dissipative effects on transverse dynamics at RHIC Tetsufumi Hirano Dept. of Physics The Univ. of Tokyo QM2008, Feb. 4-10, 2008 TH, U.Heinz, D.Kharzeev, R.Lacey and Y.Nara, Phys.Lett.B636,299(2006);arXiv:0710.5795[nucl-th].

2. Outline Motivation 3D QGP fluid + hadronic cascade model Mass ordering of v 2 (p T ) revisited Violation of mass ordering for  mesons Summary

3. Motivation To understand the QGP in H.I.C., one needs to understand the hadronic stage since Indispensable to disentangle these effects for understanding of unknowns, in particular, if one wants to extract viscous coefficient in the QGP.

4. A Hybrid Approach: QGP hydro + hadronic cascade 0 collision axis time Au QGP fluid Initial condition: Transverse  Glauber Longitudinal  “BGK triangle” QGP fluid: 3D ideal hydrodynamics (Hirano) massless free u,d,s+g gas + bag const. T c = 170 MeV Hadron gas: Hadronic cascade, JAM1.09 (Nara) T sw = 169 MeV hadron gas TH et al.(’06) (1D) Bass, Dumitru (2D) Teaney, Lauret, Shuryak, (3D) Nonaka et al., Hirano et al.

5. Pseudorapidity Distribution Tune initial parameters with T th = 100MeV to reproduce dN/deta. Then, switch to hadronic cascade below T=T sw. Caveat: Rejecting in- coming particles at T sw

6. p T spectra for pi, K, and p Reasonable reproduction of yields and spectra in low p T region (p T <~1.5 GeV/c)

7. Hadronic Dissipative Effect on v 2 Hadronic dissipation reduces v 2 as expected. Note: Early chemical freezeout (T ch =170 MeV) is implemented in pure hydrodynamic calculations.

8. v 2 (p T ) for pi, K, and p OK! Fail to reproduce data due to (absence of) fluctuation of geometry in the calcualtions. Miller&Snelling (’03), Bhalerao&Ollitrault(’06) Andrade et al (’06),Drescher&Nara (’07) Browniowski et al(’07)

9. Pseudorapidity Dependence of Elliptic Flow Again, it fails to reproduce data due to eccentricity fluctuation v 2 is largely suppressed in forward region due to hadronic dissipation. Hydro + cascade generates a right amount of elliptic flow.

10. Hydro + Cascade at Work in Forward Rapidity Regions Adopted from S.J.Sanders (BRAHMS) talk @ QM2006 hybrid model AMPT

11. Origin of Mass Ordering Mass ordering behavior results from hadronic rescatterings.  Subtle interplay btw. “perfect fluid QGP” and “hadronic corona”. b=7.2fm

12. Why they shift oppositely? protonspions pTpT v 2 (p T ) v2v2 must decrease with proper time v 2 for protons can be negative even in positive elliptic flow TH and M.Gyulassy, NPA769,71(06) P.Huovinen et al.,PLB503,58(01)

13. What happens to strangeness sector?

14. Distribution of Freeze-Out Time b=2.0fm (no decay) Early kinetic freezeout for multistrange hadrons: van Hecke, Sorge, Xu(’98) Phi can serve a direct information at the hadronization.

15.  -meson case in p T < 1 GeV/c Just after hadronizationFinal results T = T sw = 169 MeV b=7.2fm Caveat: Published PHENIX data obtained in p T >~1GeV/c for  mesons Violation of mass ordering for phi mesons! Clear signal of early decoupling!

16. phi/p Ratio as a function of p T pp collisions Pure hydro in AA collisions Hydro + cascade in AA collisions Clear signal for early decoupling of phi mesons

17. Summary A QGP fluid + hadronic rescattering Reproduction of both p T dist. and v 2 (p T,m) Reproduction of integrated and differential v 2 in forward rapidity regions Origin of mass ordering of v 2 (p T )  Radial flow effect, not “ mass effect ”.  Need QGP to get large integrated v 2. Need hadronic rescattering to get correct mass ordering. Violation of mass ordering for phi mesons  Clear signal to see this scenario  Can serve a direct information of the QGP

18. Is Mass Ordering of v 2 (p T ) a “Direct” Signal of Perfect Fluidity? STAR white paper (’05) PHENIX white paper (’05) Lines: Results from Ideal hydro Consequences of perfect fluid QGP?

19. Additive Quark Model in Transport Codes (JAM/RQMD/UrQMD) For cross sections without exp. data, Expected to be very small for phi, Omega, etc.

20. 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 /  Teaney(’03) Dissipative effect is not so large due to small expansion rate (1/tau ~ 0.05-0.1 fm -1 )

21. Excitation Function of v2 Hadronic Dissipation is huge at SPS.is huge at SPS. still affects v 2 at RHIC.still affects v 2 at RHIC. is almost negligible at LHC.is almost negligible at LHC.