TWO PARTICLE CORRELATION MEASUREMENTS AT PHENIX Takahito Todoroki For the PHENIX Collaboration University of Tsukuba & RIKEN Nishina Center Hard Probes 2012 at Cagliari, Italy 28 May 2012Hard Probes

Contents Higher harmonic event plane and flow(v n ) Correlations with v n subtractions Correlations relative to event plane - At high and intermediate p T Summary 28 May 2012Hard Probes

Motivations Dissect possible interplay of hard- scattered partons & hot dense medium To have definitive answer what remains in correlations after v n subtractions To test path length dependence of parton energy loss via correlations relative to event plane 28 May 2012Hard Probes

Initial state of collisions Initial collision geometry - Smooth to Fluctuating picture Azimuthal particle distribution  v n(even)    only v n(even)  n  + v n(odd)  n  Smooth picture Fluctuating picture  28 May 2012Hard Probes

v 3 is comparable to v 2 at 0~10% v 2 evolution as centrality increment, no evolution in v 3 v 4 {  4 } ~ 2 x v 4 {  2 } Charged particle v n : |  |<0.35 Event plane  n : |  |=1.0~2.8 PRL Charged Hadron v n at PHENIX 28 May 2012Hard Probes

Identified Particle v n Mass dependence at low p T : Hydrodynamics Baryon/Meson diff. at mid p T : Quark Coalescence 28 May 2012Hard Probes

v n contributions in correlations Contributions from v n : Ridge & Shoulder positions : Agree with v 3 peaks v n subtractions needed to get real jet correlations Ridge 2< p T asso < p T trig GeV/C Phys. Rev. C 80, (2009) Phys. Rev. C 78, (2008) ○:p+p ●: Au+Au Shoulder v 2 subtracted n=3 28 May 2012Hard Probes

Correlations with  gap v n reproduce Ri dge & Shoulder at 0-5% Track at  with EP from full FCAL  v n with EP Method v n with 2Par. Cor Method Charged particle pair with large rapidity gap e.g.  Pb+Pb 2.76TeV No Flow Subtraction ￮ measured correlations 28 May 2012Hard Probes QM’11 J. Jia ATLAS Flow Plenary

Correlations without  gap Away side shoulders are almost gone in most-central collisions 0-20% Incl.  - hadron 2-3x1-2 GeV/c PHENIX PRELIMINARY Au+Au 200GeV 0-20% 28 May 2012Hard Probes 

Correlations up to centrality 50% Away side shoulders - Canceled in most-central collisions : 0-10% - Remain in mid-central collisions : 20-50% To Do : Include v1 term to v n modulation for definitive answer V 2, V 3 & V 4 (   ) modulation by ZYAM method 28 May 2012Hard Probes

Correlations relative to event plane Control parton path length - By selecting trigger relative to forward event plane - Reduce autocorrelations of jet itself tt aa  nn ss Mid rapidity Forward rapidity 28 May 2012Hard Probes

High p T range Near side yield : No suppression Away side yield : Monotonic decrease I AA = Y AA /Y pp Short path length Long path length PRC May 2012Hard Probes v 2 & v 4 {   } modulated Au+Au 200GeV 20-60%

Intermediate p T range Constant suppression of back-to-back jet Two competitive effects seen  2 R.P. Trig. in-plane trigger case out-of-plane trigger case Au+Au 200GeV 20-50% h-h :2-4x1-2GeV/c v 2 & v 4 {   } modulated 28 May 2012Hard Probes PHENIX preliminary Flow subtracted yield is shown radially with base line. penetration dominance surface dominance

Summary Higher harmonic flow v n has been measured By v n modulation to correlations, - Shoulders almost gone in most-central collisions - Shoulders remain in mid-central collisions Correlations relative to event plane - Monotonic away side suppression at high p T - Constant suppression of di-jet & Two competitive effects at intermediate p T Fully v n modulated analyses are in progress 28 May 2012Hard Probes

Backup Slides 28 May 2012Hard Probes

 i -  j correlations 28 May 2012Hard Probes PRL

v n via event plane method Mid rapidity particle anisotropy relative to forward event planes 05-5 ZDC/SMD  dN/d  RXN in: 1.5<|  |<2.8 & out: 1.0<|  |<1.5 MPC: 3.1<|  |<3.7 BBC: 3.0<|  |<3.9 CNT: |  |<0.35 2cm Pb converter in front 28 May 2012Hard Probes RXN

Degeneracy among models disentangled by v 3 v 3 seems to prefer low viscosity  Glauber+  s  works better  CGC-KLN+  s  failed More constraints to hydrodynamics calculations V2V2 V3V3 PRL (ppg132) B. Alver et. al., PRC82, (2010). B. Schenke et. al., PRL106, (2011). H. Petersen et. al., PRC82, (2010). (Event Plane Method) 28 May 2012Hard Probes

28 May 2012Hard Probes QM’11 J. Jia ATLAS Flow Plenary

Scaling property of v 2 28 May 2012Hard Probes

Scaling property of v n v n (KE T /n q )/n q failed on v 3, v 4 & v 4 {   } v n (KE T /n q )/n q n/2 : need correction power 28 May 2012Hard Probes

Fourier decomposition of flow subtracted correlations 28 May 2012Hard Probes

Correlations relative to   28 May 2012Hard Probes