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Azimuthal HBT measurements of charged pions and kaons in Au+Au 200GeV collisions at RHIC-PHENIX

Azimuthal HBT measurements of charged pions and kaons in Au+Au 200GeV collisions at RHIC-PHENIX. WPCF2011 @ Tokyo University. Takafumi Niida from Univ. of Tsukuba for the PHENIX Collaborations. Outline. Introduction Physics Motivation Analysis PHENIX Detector Analysis flow Results

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Azimuthal HBT measurements of charged pions and kaons in Au+Au 200GeV collisions at RHIC-PHENIX

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  1. AzimuthalHBT measurements of charged pions and kaons in Au+Au 200GeV collisions at RHIC-PHENIX WPCF2011 @ Tokyo University Takafumi Niida from Univ. of Tsukuba for the PHENIX Collaborations

  2. Outline Introduction Physics Motivation Analysis PHENIX Detector Analysis flow Results Pion Azimuthal dependence of HBT radii Fourier components Kaon Azimuthal dependence of HBT radii Eccentricity at freeze-out comparing between pion and kaon Summary & Outlook WPCF2011

  3. Introduction What is HBT ? Quantum interference between identical two particles Powerful tool to explore space-time evolution in HI collisions Correlation function c2 is defined as: Bertsch-Pratt parameterization at LCMS frame Rside : transverse size of source Rout : transverse size of source + emission duration Rlong : longitudinal size of source Ros : cross term between side and out P(p1) : Probability of detecting a particle P(p1,p2) : Probability of detecting pair particles Beam Rlong detector (If assuming gaussian source) detector Sliced view Rside Rout WPCF2011

  4. Physics Motivation Azimuthal HBT analysis Measures the source shape w.r.t Reaction Plane Source shape at freeze-out is Sensitive to “system lifetime” Related to momentum anisotropy HBT Results for charged pion and kaon Centrality and mT dependence were measured for pion and kaon→No significant difference between both species How about azimuthal dependence? WPCF2011

  5. PHENIX Detector Vertex, Centrality BBC, ZDC Event plane Reaction Plane Detector(RxNP) 1<|η|<2.8 Tracking Drift Chamber, Pad Chamber PID EMCal (all sectors in west arm) |η|<0.35, ⊿φ=90° west-EMC mass square K- π- K+ π+ RxNP charge x momentum WPCF2011

  6. Analysis flow Measure the experimental C2 Correct Event Plane resolution Finite resolution reduce the oscillation amplitude of HBT radii U.Heinz et al, PRC66, 044903 (2002) Fitting C2 Sinyukov fitting method (includes coulomb correction and effect of long lived resonance decay) Get HBT radii(Rside,Rout,Rlong,…) as a fitting result R(q): relative momentum dist. of Real pairs M(q): that of mixed pairs WPCF2011

  7. Correlation function for pion Raw c2 With sinyukov’ fitting function Centrality:30-60% WPCF2011

  8. Correlation function Raw c2 With sinyukov’ fitting function Centrality:30-60% Out Long 1D Inv 3D Side R.P R.P R.P R.P WPCF2011

  9. Azimuthal dependence of HBT radii for pion Observed the oscillation for Rside, Rout, Ros Different emission duration between in-plane and out-of-plane at 0-10%? Data points are fitted by cosine series function side out Out-of-plane (⊿φ=π/2) ⊿φ In-plane (⊿φ=0) Reaction plane WPCF2011

  10. Fourier components of azimuthal HBT radii Fourier component for Rside is calculated by the following fit R2s,4 > 0 R2s,4 < 0 Relative 4th order radius seems to have negative value, But it’s zero within systematic error WPCF2011

  11. Correlation function for kaon Raw c2 with sinyukov’ fitting function Centrality: 20-60% 1D Inv 3D Side Out Long R.P R.P R.P R.P WPCF2011

  12. Azimuthal dependence of HBT radii for kaon Observed the oscillation for Rside, Rout, Ros as well as pion Data points are fitted by cosine series function side out Out-of-plane (⊿φ=π/2) ⊿φ In-plane (⊿φ=0) Reaction plane WPCF2011

  13. Final eccentricity is defined as by Blast-wave model Eccentricity at freeze-out εinitial: initial eccentricity calculated by Glauber model εfinal: final eccentricity calculated by above if εfinal= εinitial Same source shape between Initial state and freeze-out if εfinal< εinitial Source expands to In-plane direction • ・PHENIX result is consistent with STAR result for pion • ・εfinal of kaon is larger than that of pion and close to εinitial • Due to different average mT? or different cross section? WPCF2011

  14. Summary & Outlook Measurements of azimuthal dependence of HBT radii for pion and kaon in Au+Au 200GeV collisions Observed the oscillation of Rside and Rout for kaon as well as for pion 4th order in oscillation of Rside for pion is zero within systematic error Final eccentricity of pion is consistent with STAR result Final eccentricity of kaon is larger than that of pion Outlook Need to check mT dependence of final eccentricity Possible to understand the difference of pion and kaon? Comparison with model (ex. blast wave model) Azimuthal HBT w.r.t higher order event plane Analysis using 3rd order event plane is in progress Provides information about relation between v3 and source shape? ⑦ ⑧ ⑥ ⑤ ④ ③ ② Psi3 ① WPCF2011

  15. Thank you! WPCF2011

  16. Back up WPCF2011

  17. Data selection WPCF2011 • Data • Run7 Au+Au 200GeV • Track Cut • quality: 63 or 31 • pion : pt > 0.2[GeV/c] && mom<2.0[GeV/c] • kaon : pt > 0.3[GeV/c] && mom<2.0[GeV/c] • temc < 50[nsec] • 3σ matching cut @ PC3 • 3σ matching cut @ EMC • ecent > 0.1[GeV] • EMC-west(all sectors) • PID • pion: Pi<2σ && K>2σ && P>2σ • kaon: Pi>2σ && K<2σ && P>2σ • Event mixing • Zvertex: 30[bins] • Centrality: 20[bins] (10[bins] for kaon) • Reaction plane by RxP: 30[bins] (20[bins] for kaon)

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