1. Azimuthal HBT measurement of charged pions With respect to 3 rd event plane In Au+Au 200GeV collisions at RHIC-PHENIX Takafumi Niida for the PHENIX Collaboration JPS meeting, Mar. 2012

2. T. Niida JPS Mar. 2012 outline Introduction Motivation Analysis method Current status Summary and Outlook 2

3. T. Niida JPS Mar. 2012 What is HBT ? Quantum interference between identical two particles Powerful tool to explore space-time evolution in HI collisions HBT can measure the source size at freeze-out, Not whole size But homogeneity region in expanding source detector P(p 1 ) : Probability of detecting a particle P(p 1,p 2 ) : Probability of detecting pair particles 3 〜 1/R assuming gaussian source

4. T. Niida JPS Mar. 2012 Azimuthal HBT measurement “Out-Side-Long” system Source shape at freeze-out is measured relative to 2 nd order event plane  Sensitive to “system lifetime”  Related to “momentum anistropy” 4 R long : Longtudinal size R side : Transverse size R out : Transverse size + emission duration R os : Cross term between Out and Side R long Beam R side R out Beam

5. T. Niida JPS Mar. 2012 HBT and Triangular flow Can we measure triangularity by HBT ?  Answer by Blast Wave model is “Yes” S.Voloshin at QM2011 Azimuthal HBT relative to Ψ 3 will give us more detailed information of initial conditions and system evolution Centrality dependence of v 3 is very weak unlike v 2  How about triangularity at freeze-out ? 5 p T [GeV/c ] vnvn v2v2 v3v3 PRL.107, 252301(2011) Blast wave model calculation by S.Voloshin at QM11

6. T. Niida JPS Mar. 2012 Analysis method for HBT Correlation function  3 directions of Ψ 3 are not distinguished  Mixed pairs are made by event mixing Events with similar centrality, zvertex, Ψ 2 are used In this analysis, Should we consider Ψ 3 for mixed pairs? Correction of event plane resolution (U.Heinz et al, PRC66, 044903 (2002)) Coulomb correction by Sinykov‘s fit funcyion  Including the effect of long lived resonance decay 6 Ψ3Ψ3 R(q): real pairs M(q): mixed pairs q: relative momentum of pair

7. T. Niida JPS Mar. 2012 Ψ 3 dependence for different mixing conditions 7 Data: Au+Au 200GeV in PHENIX  Charged pion pairs are used “Ψ n ” mixing is applied here besides centrality and zvertex If Ψ 3 mixing is not applied, - oscillation of R side become strong - oscillation of R out become weak if both Ψ 2 &Ψ 3 mixing is applied, - Similar to Ψ 3 mixing - Is this mixing correct ? →How was Ψ 2 dependence ? Ψ 2 mixing Ψ 3 mixing Ψ 2 &Ψ 3 mixing side out 0-10% 10-20% 20-30% 30-60% Δφ=φ pair –Ψ 3

8. T. Niida JPS Mar. 2012 How was Ψ 2 dependence ? If Ψ 2 mixing is not applied, - oscillation of R side become strong - oscillation of R out become weak  Because flow(v 2 ) will be included in mixed pairs for all azimuth angle ? Similar tendency with Ψ 3 analysis At least, Ψ n mixing will be needed to see Ψ n dependence side out Ψ 2 mixing 8 without Ψ n mixing Δφ=φ pair –Ψ 2

9. T. Niida JPS Mar. 2012 Ψ 3 dependence for different mixing conditions 9 Ψ 2 mixing Ψ 3 mixing Ψ 2 &Ψ 3 mixing side out Data: Au+Au 200GeV in PHENIX  Pion pairs are used “Ψ n ” mixing is applied here besides centrality and zvertex If Ψ 3 mixing is not applied, - oscillation of R side become strong - oscillation of R out become weak if both Ψ 2 &Ψ 3 mixing is applied, - Similar to Ψ 3 mixing - Is this mixing correct ? →How was Ψ 2 dependence ? Ψ 3 mixing wll be needed Mixed-pairs should be same condition with Real pairs, so Ψ 2 mixing will be also needed This is still “work in progress” 0-10% 10-20% 20-30% 30-60% Δφ=φ pair –Ψ 3

10. T. Niida JPS Mar. 2012 Ψ 2 &Ψ 3 mixing result is compared vs AMPT  n=2 Rs and Ro have the opposite sign in oscillation  n=3 Rs and Ro have the same sign in oscillation Same tendency with current result vs Blast wave model  Different tendency in R side But both model says “Need more study” Comparison with Model S.Voloshin at QM11 side out side out Side Out AMPT Blast wave model S.Voloshin at QM11 T=100[MeV], ρ=r’ρ max (1+cos(nφ)) 10

11. T. Niida JPS Mar. 2012 Summary Azimuthal HBT measurement w.r.t Ψ 3 is in progress  Tendency of R side and R out oscillation changes by Ψ n mixing conditions.  Ψ 2 and Ψ 3 mixing will be needed to see “Ψ 3 ” dependence of HBT radii  Current result is similar to AMPT, and different from Blast wave model. This is still ”work in progress”  Further study will be done 11 Outlook Need more mixing study Acceptance study is ongoing Any simulation may be needed

12. T. Niida JPS Mar. 2012 Back up 12

13. T. Niida JPS Mar. 2012 PHENIX Detectors Vertex, Centrality  Vertex,  BBC, ZDC Event plane  Reaction Plane Detector(RxNP) Tracking  Drift Chamber, Pad Chamber PID by EMCal  Used all sectors in west arm 13

14. T. Niida JPS Mar. 2012 Correlation function for charged pions Raw C 2 for 30-60% centrality Solid lines is fit functions R.P 1D Inv 3D Side Out Long 14

15. T. Niida JPS Mar. 2012 Azimuthal HBT radii for pions Observed oscillation for R side, R out, R os Rout in 0-10% has oscillation  Different emission duration between in-plane and out-of-plane? 15 out-of-plane in-plane