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Yuting Bai (for the Collaboration)

Anisotropic Flow and Ideal Hydrodynamic Limit. Yuting Bai (for the Collaboration). International Conference on Strangeness in Quark Matter 2008 Oct. 6 -10, 2008 Beijing, China. Outline. Introduction Anisotropic flow

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Yuting Bai (for the Collaboration)

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  1. Anisotropic Flow and Ideal Hydrodynamic Limit Yuting Bai (for the Collaboration) International Conference on Strangeness in Quark Matter 2008 Oct. 6 -10, 2008 Beijing, China

  2. Outline • Introduction • Anisotropic flow • The success and uncertainties in ideal hydro calculations • Results • How much deviation from ideal hydro • Conclusions Yuting Bai, SQM2008

  3. y py px x y z x Anisotropic Flow • The spatial anisotropy is transformed into a momentum anisotropy by the multiple interactions • Established early, self-quenching, therefore sensitive to the early stage of the collisions • Depending on rescattering, sensitive to the degree of thermalization reaction plane Yuting Bai, SQM2008

  4. Ideal hydro success and uncertainties C. Alt et.al; Phys.Rev.C68,034903(2003) Hydro limits from P.Kolb, J.Sollfrank,U.Heinz; Phys.ReV.C62:054909,2000 • v2/e was considered to approach the ideal hydro limit in central collisions • Uncertainties: • Choice of EoS - affects Hydro limits • The initial conditions: Glauber, Color Glass Condensate (CGC) Yuting Bai, SQM2008

  5. y’ y x’ x Choices of v2 and e • The number of individual nucleons participating in the collision as well as their position could fluctuate from event to event. The center of the overlap zone can be shifted and the orientation of the principal axes of the interaction zone can be rotated • v2{EP}, v2{2}, epart and e{2} sensitive to anisotropy w.r.t the participant plane YPP • v2{4},v2{ZDCSMD} and estdsensitive to anisotropy w.r.t the reaction plane YRP YPP YRP M.Miller and R.Snellings;nucl-ex/0312008 R.Bhalerao and J- Y.Ollitrault; Phys.Lett.B 614(2006)260 S.Voloshin, A.Poskanzer, A.Tang and G.Wang; Phys.Lett.B 659(2008)537 Yuting Bai, SQM2008

  6. STAR Preliminary Flow increases • Scaled v2 increases with centrality over large pt range • Peak position of v2/e shifts to higher pt in more central collision • The system seems more close to thermalization for most central collisions standard eccentricity from Glauber model eccentricity from CGC (nucl-th/0605012) Yuting Bai, SQM2008

  7. How much deviation from ideal hydro • Try to use the data to constrain the hydro limit • Use relativistic Boltzmann calculations to calculate how v2 approaches hydro as function of cross section and density • Based on these calculations the v2/e dependence has been parameterized as function of K • Fit data to extract v2hydro/e and s R.Bhalerao,J-P.Blaizot,N.Borghini and J-Y.Ollitrault;Phys.Lett.B 627:49-54,2005 C.Gombeaud and J-Y.Ollitrault; Phys. Rev. C 77, 054904 (2008) H-J.Drescher, A.Dumitru, C.Gombeaud, J-Y.Ollitrault; Phys. Rev. C 76, 024905 (2007) Yuting Bai, SQM2008

  8. STAR Preliminary How much deviation from ideal hydro • The estimates depend on the initial conditions. A softer EoS is required for CGC • Ideal hydro limit is not reached at top RHIC energy. The ratio of v2/e is considerably away from hydro limit independent of choices of e • K decreases with the increasing of particle density. But still finite in the most central collisions Yuting Bai, SQM2008

  9. STAR Preliminary Hiroshi Masui Parallel Session I: 15:40—16:00 How much deviation from ideal hydro • With the assumption that parton cross section (s) is same for all identified particles, a universal trend of approaching hydro limit is established. In central collisions, the ratio of v2/e is considerably away from hydro limit PHENIX p, K and p: nucl-ex/0604011, STAR Ks0, L: Phys. ReV. C 77 054901 (2008) Yuting Bai, SQM2008

  10. STAR Preliminary Constraint on EoS Yuting Bai, SQM2008

  11. Constraint on h/s Temperature from: A.Adare nucl-ex/08044168 STAR Preliminary Yuting Bai, SQM2008

  12. STAR Preliminary Charged particle v4/v22 • It’s expected that v4/v22 decreases with K-1. • Consistent with Boltzmann calculation with K> 0.5 • Measured ratios indicate that ideal hydro limit is not reached Hydro, Boltzmann calculations:J-Y. Ollitrault Yuting Bai, SQM2008

  13. Conclusions • v2/e, examined with transport motivated formula, approaches ideal hydro limit for all identified hadrons. In central Au+Au collisions, v2/e is still considerably away from Hydro limit. The conclusion is independent of initial conditions. • Results of charged hadron v4/v22 areconsistent with above • Constraint on EoS obtained. • For the first time, h/s versus centrality is extracted. Yuting Bai, SQM2008

  14. Choices of v2 and e v2{4}: measured with the 4-particle cumulant method v2{ZDCSMD}: measured with the first order event plane reconstructed with STAR’s ZDC-SMD non-flow effects are reduced in both methods STAR Preliminary G. Wang QM2005 Au +Au 200 GeV Yuting Bai, SQM2008 14

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