First Results on Two-Particle Correlations Determined by PHENIX

1. First Results on Two-Particle Correlations Determined by PHENIX Stephen C. Johnson Lawrence Livermore National Lab for the PHENIX Collaboration Stephen C. Johnson for the PHENIX Collaboration

2. C2 1/R q Why study particle correlations?(Preaching to the choir) p1 • Measures the relative spatial-temporal separation at the point of last interaction • Sensitive to relative separation in phase space of pairs at freeze-out p2 q p1 p2 2 Assuming a chaotic source with no dynamical correlations and no final state interactions the resulting correlation function is rather straight-forward: Stephen C. Johnson for the PHENIX Collaboration

3. ** RO RS RS2+b2t2=RO2 Be careful with assumptions of symmetric and static sources!! bflow But Beware!! e.g. • “C2 depends on more variables than you can think of.” • Anonymous HBT expert • In particular • Dynamical correlations • Lorentz kinematics **This first figure unabashedly stolen from M. Lisa Stephen C. Johnson for the PHENIX Collaboration

4. Agenda • First PHENIX HBT results from Run 1. • Proof of principle – capability of PHENIX to perform these measurements • PID capabilities and analysis • 1D correlations • Bertsch-Pratt 3D fit to ROSL • Confirm dependencies of R on kt • Comparisons and Conclusions • A glance at future capabilities. Stephen C. Johnson for the PHENIX Collaboration

5. For this analysis: p = • 2 s within p peak • 3 s away from K peak • 180<p< 2000 MeV/c Time of flight with TOF & Beam-Beam Counter “Particle identification capability of the PHENIX experiment” H. Hamagaki Tracking with Drift Chamber/Pad Chambers Particle identification Stephen C. Johnson for the PHENIX Collaboration

6. Pair Acceptance • Acceptance about time-of-flight wall restricts correlation measurement to ypair<.3 • PHENIX excellent PID allows pair reconstruction to very high kt • => larger statistics of year-2 will allow high kt 3D measurements Low q pairs All pairs Raw Counts (A.U.) Stephen C. Johnson for the PHENIX Collaboration

7. kt q Acceptance • Finite acceptance in dy and df => finite qTside and qlong reach. • Excellent particle identification to large p => large qTout bite. ~qout qlong ~qTside Stephen C. Johnson for the PHENIX Collaboration

8. q acceptance Stephen C. Johnson for the PHENIX Collaboration

9. PHENIX Preliminary Centrality • All data presented today are for ‘minimum bias collisions’ (i.e. only with trigger on zvtx) • However: finite detector + minimum bias sample + pairs requirement • => bias towards central collisions in min bias sample • Truly a central event sample Stephen C. Johnson for the PHENIX Collaboration

10. Qinv distributions PHENIX Preliminary • Full coulomb correction… • Analytic coulomb correction assumes R(Qinv) source • Resulting radii independent of RQinv input within ~10% • Qinv => measurement of relative separation of the pair in the pair rest frame • Acceptance dependent!! C2 Qinv (MeV/c) Stephen C. Johnson for the PHENIX Collaboration

11. Bertsch-Pratt Fit Results • Rl = 6.7  .9 • RTside = 5.8  1.5 • RTout = 5.49  .54 • L = .493  .061 • Rl = 4.0  1.2 • RTside = 7.9  1.1 • RTout = 6.23  .54 • L = .493  .050 Stephen C. Johnson for the PHENIX Collaboration

12. R=6.0  .8 l=.38  .08 R=4.8  .5 l=.48  .08 R=3.7  .6 l=.37  .09 p- p- C2 PHENIX Preliminary R=6.5  .9 l=.38  .08 R=4.5  .6 l=.28  .05 R=4.5  .5 l=.34  .06 p+ p+ q (MeV/c) 1D correlations • Full coulomb correction • q =>Measure of relative separation of pair in the rest frame of the collision. Stephen C. Johnson for the PHENIX Collaboration

13. As a function of kt PHENIX Preliminary • kt dependence is well behaved • Measured relative separation of pions from source expected to decrease versus kt possibly due to collective behavior of source or resonance contributions. Stephen C. Johnson for the PHENIX Collaboration

14. Star Preliminary (M. Lisa) NA44 NA49 E866 E895 PHENIX Preliminary Comparisons • No indication of large volumes • Comparable results to SPS and preliminary STAR with similar <kt>/centrality • Not exactly the same, so be careful… • Perhaps indicative of same effective freeze-out due to convolution of • larger source and • stronger dynamical correlations / high flow velocities / resonances(?) root-s Stephen C. Johnson for the PHENIX Collaboration

15. Conclusions* • First measured p+/- correlation function from PHENIX at RHIC including most Run 1 dataset: • 1D correlation looks well behaved => used to determine coulomb correction. • 3D correlation comparable to SPS published and STAR preliminary results when comparing similar kt bins • Dependencies of Rl and Rs on beam energy are gradual and well behaved. • No indication of long lived source in correlation function • But be careful what you conclude from that… • First proof-of-principle methodology -- looking forward to increased statistics and systematic studies… * Don’t leave yet, I still have 3 more slides… Stephen C. Johnson for the PHENIX Collaboration

16. Coherent interpretation of source size For the future... • This year • Complete systematic studies of p+/p- correlations • h-h-p-p, p-K (1D) • with EMCAL: • pp, KK, pp (1D) • Next year • 100x statistics => • p vs centrality and kt • pp, KK • with EMCAL • anti-neutron, p0 (?) • In general • Are there other methods we can use to extract info from correlations? ==> Stephen C. Johnson for the PHENIX Collaboration

17. Other methods See poster by D. Brown • Explicit inversion of correlation function to deduce relative separation of pairs at freeze-out. • How sensitive is this method to the source? • Can we learn more than just the RMS? • Extract multi-D source parameters? • Systematic studies underway. Figure and studies by Mike Heffner Brown and Danielewicz nucl-th/0010108 Stephen C. Johnson for the PHENIX Collaboration

18. R. Soltz M. Heffner Special Thanks Stephen C. Johnson for the PHENIX Collaboration