1. Measurement of v 2 and v 4 in Au+Au Collisions at different beam energy from PHENIX Shengli Huang for PHENIX Collaboration Vanderbilt University

2. Outline  1. Physics motivations  2. The analysis methods  3. The v 2 measurements from PHENIX  4. The v 4 measurements from PHENIX  5. Summary and Outlooks 2S. Huang WWND2011,Colorado

3. Physics motivation (1) S. Huang3 M. Luzum, J-Y Ollitrault, Phys.Rev.C82:014906,2010 RHIC data indicates the partonic collectivity has been generated at RHIC. Viscous hydro-dynamics calculations with a small value of η/s is compatible with v 2 measurements Beam energy scan will search for the collision energy where the partonic matter starts to turn off WWND2011,Colorado η/s = 0.08 CGC η/s = 0.16 Glauber

4. Physics motivation (2) 4S. Huang  The differential v 2 saturates at RHIC energy from 62.4 GeV to 200 GeV Softening of equation of state  Locate the collision energy for the critical point searching  To measure the v 2 and v 4 in same rapidity for the same collision system will supply better information for extracting collision energy dependence Phys.Rev.Lett.94:232302,2005. WWND2011,Colorado

5. Physics motivation (3) S. Huang5  v 4 /v 2 2 is sensitive to the η/s and the freez-out temperature  Simultaneous measurements of differential v 2 and v 4 are important for extraction of transport properties Gombeaud & J-Y.Ollitrault, PRC 81,014901(2010) Luzum, &,J-Y. Ollitrault, PRC 81,054910(2010) Phys. Rev. Lett. 105, 062301 (2010) WWND2011,Colorado

6. PHENIX Detectors for Event Plane 6S. Huang  Large η gap away central arm |η|<0.35  Systematic study the non-flow effect for the measurement of v 2 and v 4 Event plane detectors: Reaction plane detector RXN IN (1.5<|  |<2.8) RXN OUT (1.0<|  |<1.5) Muon position EMCal MPC (3.1<|  |<3.9) Beam-beam counter BBC (3.1<|  |<3.9)

7. The event plane Resolution S. Huang7 σ RP for v 2, Au+Au at 7.7 GeV WWND2011,Colorado

8. Robust Measurements S. Huang8 The measurements from different event plane detectors are consistent quite well WWND2011,Colorado

9. The Energy dependence of v 2 (1) S. Huang9 There is no energy dependence of v 2 (p T ) for collision energy from 39 GeV to 200 GeV for different collision centrality bins WWND2011,Colorado

10. The Energy dependence of v 2 (2) S. Huang10 The v 2 at 7.7 GeV Au+Au is much lower than v 2 of 39 GeV, 62.4 GeV and 200 GeV Partonic flow --  Hadronic flow ? WWND2011,Colorado

11. The Baryon contribution S. Huang11 Proton yield dominates in the positive hadrons, while pion yield dominates in the negative hadrons The v 2 of negative hadron at 7.7 GeV Au+Au is lower than v 2 of pion at 200 GeV AuAu WWND2011,Colorado

12. The Energy dependence of v 4 (1) S. Huang12 Similar to v 2, the v 4 does not show energy dependence for collision energy from 39 GeV to 200 GeV WWND2011,Colorado

13. The Energy dependence of v 4 (2) S. Huang13 At mid-centrality, the v 4 /v 2 2 is around 0.8 as a function of p T in Au+Au collision from energy 39 GeV to 200 GeV The v 4 /v 2 2 is similar from 39 GeV to 200 GeV at different N part in Au+Au collisions WWND2011,Colorado

14. Summary and outlooks 1. The v 2 measurement from PHENIX further indicates that the v 2 saturates from 39 GeV to 200 GeV, but larger than the v 2 of 7.7 GeV in AuAu collision 2. The v 4 also saturates from 200 GeV to 39 GeV and the v 4 /v 2 2 is almost constant from 39 GeV to 200 GeV 3. These results will supply new information for comparison with results from viscous hydro-dynamics models. It will also shed light on the path for further research on the critical point 4. The PID v 2 and v 4 results from PHENIX will be out soon S. Huang14 WWND2011,Colorado