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Hadronic dissipative effects on transverse dynamics at RHIC

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

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Hadronic dissipative effects on transverse dynamics at RHIC

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

  2. Outline • Motivation • 3D QGP fluid + hadronic cascade model • Mass ordering of v2(pT) revisited • Violation of mass ordering for f 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 TH et al.(’06) hadron gas • Initial condition: • Transverse  Glauber • Longitudinal  “BGK triangle” • QGP fluid: • 3D ideal hydrodynamics • (Hirano) • massless free u,d,s+g • gas + bag const. • Tc = 170 MeV • Hadron gas: • Hadronic cascade, JAM1.09 • (Nara) • Tsw = 169 MeV time QGP fluid collision axis 0 Au Au (1D) Bass, Dumitru (2D) Teaney, Lauret, Shuryak, (3D) Nonaka et al., Hirano et al.

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

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

  7. Hadronic Dissipative Effect on v2 Hadronic dissipation reduces v2 as expected. Note: Early chemical freezeout (Tch=170 MeV) is implemented in pure hydrodynamic calculations.

  8. v2(pT) for pi, K, and p 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) OK!

  9. Pseudorapidity Dependence of Elliptic Flow Again, it fails to reproduce data due to eccentricity fluctuation v2 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 hybrid model AMPT Adopted from S.J.Sanders (BRAHMS) talk @ QM2006

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

  12. Why they shift oppositely? pions protons v2(pT) v2 <pT> pT v2 for protons can be negative even in positive elliptic flow must decrease with proper time P.Huovinen et al.,PLB503,58(01) TH and M.Gyulassy, NPA769,71(06)

  13. What happens to strangeness sector?

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

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

  16. phi/p Ratio as a function of pT • 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 pT dist. and v2(pT,m) • Reproduction of integrated and differential v2 in forward rapidity regions • Origin of mass ordering of v2(pT) Radial flow effect, not “mass effect”. Need QGP to get large integrated v2. 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 v2(pT) 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 • 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))

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

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