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Energy dependence of the Bose-Einstein Correlations

Energy dependence of the Bose-Einstein Correlations. Sergey Panitkin RHIC/AGS User Meeting 2006. Outline . Introduction Energy dependence of pion correlations Azimuthally sensitive pion HBT Summary. Two-particle Correlations. Single particle spectrum is sensitive to momentum

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Energy dependence of the Bose-Einstein Correlations

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  1. Energy dependence of the Bose-Einstein Correlations SergeyPanitkin RHIC/AGS User Meeting 2006 Sergey Panitkin

  2. Outline • Introduction • Energy dependence of pion correlations • Azimuthally sensitive pion HBT • Summary Sergey Panitkin

  3. Two-particle Correlations Single particle spectrum is sensitive to momentum distribution only Relative momentum distribution of particle pairs is sensitive to space-time information FSI Source function Basis for Identical and Non-identical particle femtoscopy System evolution encoded in S(r,q) Sergey Panitkin

  4. Hanbury Brown-Twiss interferometry Rlong p1 x1 p2 qside Rside x2 qout qlong Rout • HBT: Quantum interference between identical particles 2 C (q) Gaussian model (3-d): 1 • Final-state effects (Coulomb, strong) also can cause correlations, need to be accounted for q (GeV/c) • Pratt-Bertsch parameterization Sergey Panitkin

  5. HBT for Gaussian sources Decompose q into components: qLong: in beam direction qOut : in direction of transverse momentum KT qSide:  qLong & qOut Radii are related to source variances: Sensitive to emission time Sensitive to transverse extent Sensitive to longitudinal extent In Longitudinally Co-Moving System (LCMS) bl =0 Sergey Panitkin

  6. Mt dependence Charged pions, AuAu (PbPb) most central Mt dependence is attributed to collective flow Sergey Panitkin

  7. Femtoscopic signature of QGP Rischke & Gyulassy, NPA 608, 479 (1996) with transition G. Boyd et al., , Nucl.Phys. B469 (1996) 419 3D 1-fluid Hydrodynamics “” • Long-standing signature of QGP: • Lattice QCD -> Speed of sound goes to zero (pressure drop) at phase transition • increase in , ROUT/RSIDEdue to deconfinement  confinement transition • hoped-for “turn on” as QGP threshold is reached (“softest point”) Sergey Panitkin

  8. Compilation of world BP 3D -HBT parameters as a function of s The HBT Excitation function circa 2001 • ~10% Central AuAu(PbPb) events • y ~ 0 • kT0.17 GeV/c • no significant rise in spatio-temporal size of the  emitting source STAR Preliminary QM 2001 Sergey Panitkin

  9. Energy systematics 2006 • Many new measurements since 2001 • Same conclusions Sergey Panitkin

  10. <r> [c] Tth [GeV] STAR Kinetic freezeout from AGS->RHIC Blast wave fits to spectra <ßr> (RHIC) = 0.55 ± 0.1 c TKFO(RHIC) = 100 ± 10 MeV • Rapid change in freeze-out temperature and flow velocity between 2-20GeV • Explosive Transverse Expansion • at RHIC  High Pressure • Almost constant freeze-out temperature above 20 GeV T. Nayak Sergey Panitkin

  11. Freeze-out volume vs. beam energy CERES Phys. Rev. Lett. 90 (2003) 022301 <kt> ~ 0.16 GeV/c √s(GeV) Freeze-out volumeestimate: • Not a simple concept for expanding sources with continuous emission • Because of flow the best “total volume” estimate is at low Kt • Ad hoc formula • non-monotonic behaviour • minimumbetween AGS and SPS • Why there is a drop at AGS ? H. Appelshauser Sergey Panitkin

  12. Freeze-out volume 0.15 < kt < 0.25 GeV/c <Npart> Freeze-out volumeestimate: Centrality dependence: CERES Phys. Rev. Lett. 90 (2003) 022301 since  ???? only at given beam energy!! Sergey Panitkin

  13. Particle multiplicity vs. beam energy CERES Phys. Rev. Lett. 90 (2003) 022301 • particle number increases monotonically •  freeze-out at constant density excluded • chemical composition changes • cross sections are very different •  try mean free path: √s(GeV) Sergey Panitkin

  14. Mean free path CERES Phys. Rev. Lett. 90 (2003) 022301 in a composed medium: √s(GeV) • also Nσshows non-monotonic behaviour • dominated by baryons at low energy and mesons at high energy Sergey Panitkin

  15. Universal pion freeze-out CERES Phys. Rev. Lett. 90 (2003) 022301 • Nσ follows Vf • data are consistent with constant mean free path at freeze-out independent of beam energy and centrality √s(GeV) Sergey Panitkin

  16. Universal freeze-out II H. Appelshauser • universal pion freeze-out: • independent of beam energy and • system size • in A-A: lf << R • why no dependence on beam energy and system size? • why so small? lf (fm) sqrt(sNN) (GeV) ..implies f.o. at constant density (R~(dNch/dh)1/3) if particle ratios are constant! Sergey Panitkin

  17. What is “true” scaling variable? STAR Preliminary Nch seems to be better Sergey Panitkin

  18. Multiplicity scaling of radii STAR DATA (pp,dAu,CuCu,AuAu@62GeV - prelim.) “Universal radii scaling” as a concequence of volume scaling Multiplicity scaling seems to work at all measured Kt For different systems and energies at RHIC physics does not change!? Sergey Panitkin

  19. HBT relative to reaction plane HBT() later hadronic stage? beam into screen x b • “Standard” HBT provides direct access to space-time (size) information about source, "HBT radii" • Additionally, HBT() provides direct access to shape and orientation of source • Source shape at freeze-out  evolution of system"How much of initial spatial deformation still exists at freeze-out?" collective expansion of system Heinz & Kolb, Nucl.Phys. A702 (2002) 269-280 Sergey Panitkin

  20. Elliptic geometry leads to oscillations of the radii For example Rside HBT with respect to reaction plane Out-of-plane Circular In-plane Rside2 (fm2) f (degree) fp=90° Rside (small) Rside (large) Reaction plane fp=0° out-of-plane extended source Naïve view with no flow Heinz, Hummel, Lisa, Wiedemann PRC 044903 (2002) Sergey Panitkin

  21. Predictions from hydro later hadronic stage? in-plane-extended out-of-plane-extended • Hydrodynamics: initial out-of-plane anisotropy may become in-plane kT dependence Heinz & Kolb, hep-ph/0111075 Teaney, Lauret, & Shuryak, nucl-th/0110037 Sergey Panitkin

  22. Centrality Dependence of HBT() STAR • Lines represent fits to allowed oscillations: out, side, long go as cos(2) out-side goes as sin(2) • 12 -bin analysis (kT integrated) • 15° bins, 72 CF's total12 bins × 3 centrality bins × 2 pion signs • 0.15 < kT < 0.65 • Oscillations exist in transverse radii for all bins • Amplitudes weakest for 0-10% Sergey Panitkin

  23. Estimate of initial vs F.O. source shape FO = INIT RHIC1 [Kolb & Heinz] • estimate INIT from Glauber • from asHBT: • FO < INIT→ dynamic expansion • FO > 1 → source always OOP-extended • constraint on evolution time • Out of plane extended source • Short life time Sergey Panitkin

  24. AGS: FO  init RHIC: FO < init (approximately same centrality) sNN (GeV) Exitation function • AGS: E895, RHIC: STAR • does it make sense? Is it related to bulk dynamics? • YES • AGS: E895, RHIC: STAR • ~200 GeV Gap in measurements Sergey Panitkin

  25. Summary • HBT is a valuable tool for studies of space-time structure of systems created in heavy ion collisions • Important additional constraint for spectra and v2 measurements • Large systematic datasets are already collected from AGS, SPS and RHIC • Non-trivial energy dependence of HBT radii is observed • No predicted signatures of 1st order phase transition are not (yet?) observed • Non monotonic behaviour (dip) around 10 GeV • “CERES hypothesis” is tempting: Universal mean free path at f.o.? • Similar dynamics, hence chemistry drives freeze-out • Multiplicity scaling at SPS and RHIC • Azimuthally sensitive HBT provides additional unique information about reaction dynamics • Detailed measurements at RHIC (and AGS), no measurements at SPS • Out of plain extended sources observed, imply short (~10 fm) source lifetime • More measurements are needed • Lower energy measurements around 10-20 GeV will be very interesting Sergey Panitkin

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