1. 1 2-particle correlation at RHIC Fabrice Retière, LBNL for the STAR collaboration

2. 2 Outlines Hydro at RHIC Rather successful for spectra and elliptic flow But, cannot describe pion HBT A blast wave model? Very strong flow Short emission duration More constraints : new 2-particle correlations from STAR Pion HBT with respect to the reaction plane Kaon HBT Kaon – pion correlations

3. 3 R tt Rside Rout Kt = pair Pt Blast wave features Interplay between flow and temperature Correlation position - momentum Short emission duration Hydro lower limit +-+- Rout (fm) 6 0.2 0.3 Pt (GeV/c) 5 4 6 5 4 1 0.9 0.8 Model : R = 13.5 fm,  = 1.5 fm/c T = 110 MeV, = 0.52c 0.1 Rside (fm) Rout/Rside Data, Phys.Rev.Lett. 87, 082301 (2001) Pion HBT explained in a blast wave scenario

4. 4 Other blast wave model success Spectra and elliptic flow -- K-K- p 1/m T dN/dm T (a.u.) m T - m [GeV/c 2 ] Additional features for v2 Momentum and position anisotropy STAR preliminary Submitted to PRL Masashi Kaneta A. Poskanzer, R. Snellings, S.Voloshin

5. 5 HBT and Elliptic flow Oscillations From flow From space asymmetry Rside 2 (fm 2 ) without flow Only space asymmetry  (deg)  =0 degree Rout large Rside small  =90 degree Rout small Rside large In plane example

6. 6 HBT and Elliptic flow Result from STAR Clear in-plane oscillation Blast wave fit R=10 fm, T=110 MeV, = 0.52c Consistent with other measurements Favor a scenario with an anisotropy both in space and momentum STAR preliminary Randy Wells, Mike Lisa

7. 7 More constraints to the blast wave model : mass dependence KpKp m T (GeV/c 2 ) 0. 0.20.40.60.81.1.2 0.4 (a.u.) Blast wave 0.5 0.6 NA44 @ SPS PRL 87 (2001) 112301

8. 8 Mass scaling? Kaon HBT STAR preliminary Rinv = 4.5 ± 0.3 fm (stat) Coming soon 2D/3D HBT Needed for comparison to the blast wave model Qinv (GeV) C(Qinv) Sergei Panitkin

9. 9 Kaon – pion correlation Static sphere : R= 7 fm ± 2 fm (syst+stat) Blast wave T = 110 MeV (fixed) = 0.52c (fixed) R = 13 fm ± 4 fm (syst+stat) Consistent with other measurements STAR preliminary

10. 10 Probing the space-time emission asymmetry Kinematics selection Catching up  Large interaction time  Large correlation Moving away  Small interaction time  Small correlation Ratio  Sensitive to the space-time asymmetry

11. 11 Space-time asymmetry Evidence of a space – time asymmetry   -  K ~ 4fm/c ± 2 fm/c, static sphere Consistent with “default” blast wave calculation Kaon = 0.42 GeV/c Pion = 0.12 GeV/c STAR preliminary

12. 12 Conclusions and outlook New measurements from STAR : Pion HBT with respect to reaction plane Kaon HBT Kaon-pion CF Qualitative agreement with a blast wave scenario But, so far, cannot be achieved by any hydro or microscopic model Next Pion HBT @ 200 GeV (and others) More statistics for reaction plane dependence Different mass 3D K +,K -, proton, K 0 s,  More non-identical Pion-proton Proton-  @ 200GeV Pion-  - @ 200GeV?

13. 13 First sign of emission asymmetry @ RHIC

14. 14 Strong flow and short emission duration at RHIC Consistent with Spectra Elliptic flow Pion HBT Pion HBT wrt reaction plane Pion – kaon correlation function Question for theorists How to get there? Kaon = 0.42 GeV/c Pion = 0.12 GeV/c

15. 15 Back up

16. 16 Kaon Hbt 7 MeV/c bins Positive Kaons, Mult 3 (~11% Central), Pt 150-400 MeV/c, |y|<0.3 Qinv (GeV/c)

17. 17 Kaon Hbt and coulomb

18. 18 Chi2 contour T th [GeV]  s [c] T th [GeV]  s [c]

19. 19 error contour from elliptic flow data color:  2 levels from HBT data

20. 20 Equations