Systematic study of the away side jets in AuAu collisions Jiangyong Jia, Columbia University

1. Systematic study of the away side jets in AuAu collisions Jiangyong Jia, Columbia University for the PHENIX Collaboration Centrality Au + Au h - h results ZYAM subtracted per-trigger yield, the red/green lines are uncertainty from v2 subtraction. The 15% uncertainty on the single efficiency not included. Away side jet shape has a systematic evolution as function both pT and centrality. In particular in central collisions, the away side peak reappears at high pT Compare Au+Au and Cu + Cu p0 – h correlation function Cu+Cu 0-10% Npart = 98, it is comparable to Au+Au 30-40% Npart = 114. The jet shape can be compared directly! Similar trend Au+Au PHENIX preliminary Cu+Cu pT v2 background is scaled to match the correlation function (ZYAM). This is the method used to extract jet yield. ZYAM method Evolution of the away side jet shape ZYAM over-subtract the jet yield, but the away side jet shape is not sensitive to the pedestal level . In addition, since the away side is so flat, it indicate that the the dip after the v2 subtraction is unavoidable Quantify the away side jet yield • Quantify the jet yield in three regions: • Near jet |Df|<p/3. • Away (center) dip |Df-p|<p/6, • Away peaks(wing) p/2 <Df-p<5p/6, 7p/6 <Df-p<3p/2 Correlation function and v2 background Subtracted jet yield The away side volcano shape Different trigger window w.r.p the reaction plane We select a particular trigger direction [45° - 60°] w.r.p event plane. This window has a small but positive v2. The correlation function shows a clear dip structure even before v2 subtraction The six trigger windows used Trigger: 2.5 – 4 GeV/c The Difference of the per-trigger yield between in plane (bin1) and out of plane (bin6). The difference is dominated by the remaining v2 and v4, but there is small asymmetry which might reflects the RP dependence of the medium modification In most central collisions, most of the away side pairs are from the double peaks. In mid-central and peripheral collisions, the yield in the center of away side dominate. The ratios shows more clearly both the centrality and pT dependence of the away side center and wing region relative to the near side jet. The contribution of the away center region increases for more peripheral and higher pT bin. The normalization in all trigger bins are common (x), which is fixed by the integrated bin, so the v2 curves on various bins are fixed! • Cross at ±p/4, p± p/4 almost perfectly. • jet yield show small or no dependence on orientation • in those locations • The away side crossing point is higher than • that at the near side (away side jet contribution) • Displaced maximum and minimum around p/2. • Due to away side jet contributions Formula derived from Phys.Rev. C69 (2004) 021901, J. Bielcikova, S. Esumi, K. Filimonov, S. Voloshin, J. P. Wurm The per-trigger yield after v2 subtraction. Remember, v4 is not subtracted. Also the correlated uncertainty on v2 remains.