Rui Wei Nuclear Chemistry Group Stony Brook University for the PHENIX Collaboration

1. Reaction Plane Dependent Jet-suppression and Azimuthal Anisotropy at high pT in Au+Au Collisions at PHENIX Rui Wei Nuclear Chemistry Group Stony Brook University for the PHENIX Collaboration

2. Outline • Motivation: • Why we are interested in high pT azimuthal anisotropy • Experimental approach: • How to measure the anisotropy • Results discussion • v2(pT, centrality) • RAA(Df, pT, centrality) • Comparisons to model calculations • Summary

3. PRL. 91, 182301 (2003) S.Bass arXiv:0808.0908 arXiv:0903.4886 Motivation • Azimuthal anisotropy (v2) measurement: • Low pT: well described by hydrodynamics; • Intermediate pT: recombination + hydro; • High pT: jet suppression? • Study their relations with the initial geometry. • Discriminating power of RAA is not enough: • All jet quenching models work well. • But with large discrepancy of extracted transport coefficient q-hat: • HT: 2.3 GeV2/fm • AMY: 4.1 GeV2/fm • ASW: 10 GeV2/fm • Differential angular measurements of RAA: • Run4 results • Help to discriminate between models • High pT: limited by statistics

4. Relative yields corrected by R.P resolution PHENIX Preliminary 30-40% Experiment Measurements • Azimuthal anisotropy (v2): • Particle yields w.r.t. the reaction plane • Corrected for R.P. resolution • p0s in this analysis; • RAA(Df): Multiply By inclusive RAA

5. Reaction Plane Detectors • Run4: BBC (3<|h|<4); • Run7: • MPC (3.1<|h|<3.9) • RXNin (1.5<|h|<2.8) • RXNout (1.0<|h|<1.5) • Provide better R.P. resolution • RXNout is biased by jets; • Closer to central arm. • MPC is used: • Same rapidity window as BBC; • ~40% better resolution;

6. Run4 Results Submitted for publication: arXiv:0903.4886

7. Preliminary Run7 p0 v2 results • We extended pT range up to 13GeV/c in each centrality bin; • Sizeable v2 at high pT is observed, and is relatively flat;

8. p/2 0 RAA(Df, pT) results In-plane Out-of-plane Grey bands: Error in RAA

9. p/2 0 Comparisons to model calculations Implication: large q-hat for the medium? Calculation from S.Bass et al arXiv:0808.0908

10. Calculations for other centralities? Comparisons in other centralities needed.

11. v2 vs Npart • High pT v2 is lower; • How is v2 related to the initial geometry? • Low pT: saturated at central; • High pT: more linear;

12. v2 Comparisons to Geometric Models • E.Shuryak: PRC 66 027902 (2002) • Geometric limit: v2(high pT) < v2max(b) • Too large for a pure “jet quenching” • A.Drees, H.D.Feng, J.Jia: Phys.Rev.C71:034909,2005 • Jet absorption proportional to matter density; • Can’t reproduce the large v2. • V. Pantuev: arXiv:hep-ph/0506095 • Corona effect, L ~ 2fm; • J.Liao and E.Shuryak: arXiv:0810.4116 • Stronger jet quenching at near-Tc region; physics beyond pQCD?...

13. p/2 0 in-plane out-of-plane Out-of-plane vs. in-plane pT • Low pT: relatively flat at the out-of-plane direction; • Geometric dependences are different for two orientations. RAA NPart

14. Summary • Presented detailed measurements of RAA and v2: • With enhanced statistics and improved reaction plane resolution; • v2(pT, Npart) measured up to 13GeV/c; • Measurements indicate: • v2 is sizeable and relatively flat at high pT; • RAA show strong angular dependence relative to the reaction plane. • Initial additional constraints obtained via RAA and anisotropy using 20-30% centrality data; • HT describes in-plane results; • AMY describes out-of-plane results; • ASW qualitatively describes both in-plane and out-of-plane results; • Implication: large q-hat value for the medium? • Comparisons with other centralities needed. • comparisons to geometrically inspired models.

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