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Resonances in Heavy Ion Collisions

Resonances in Heavy Ion Collisions. Introduction History/Techniques Particle Yield Thermal Description Strangeness Enhancement In-medium Effect Time Scale Measurement pT Spectra Flow Effect High pT Phenomenon. O. Barannikova, M. Bleicher, G. Brown, P. Fachini, L. Gaudichet ,

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Resonances in Heavy Ion Collisions

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  1. Resonances in Heavy Ion Collisions • Introduction • History/Techniques • Particle Yield • Thermal Description • Strangeness Enhancement • In-medium Effect • Time Scale Measurement • pT Spectra • Flow Effect • High pT Phenomenon O. Barannikova, M. Bleicher, G. Brown, P. Fachini,L. Gaudichet, T. Hallman,H. Huang, F. Laue, H. Long, R. Longacre, J. Ma, C. Markert , S. Salur, J. Sandweiss, E. Shuryak, A. Tai, G. Torrieri, T. Ullrich, N. Xu, E. Yamamoto, H. Zhang

  2. With the establishment of the hydrogen bubble-chamber, entirely new possibilities for research into high-energy physics present themselves. Results have already been apparent in the form of newly-discovered elementary particles. The first, very short-lived, so called, "resonance particle" was found in 1960. The Nobel Prize in Physics 1968 First time Invariant Mass was used (bump hunting) A little bit of history  (1952?) (1385) (1960) (892) (1961) (1405)   1411 (1967)

  3. ISR STAR Preliminary K*0 from p+p Collisions Measurement Technique • Mixed-event, Like-sign Background subtraction • P-Wave Breit-Wigner function or Modified BW H. Zhang (STAR)

  4. How Many Resonances?

  5. How Many Measured? How are we doing so far? e+e-: 50 particles AA: 16 Including stable particles

  6. Experiments

  7. What do we do with it? e+e- Y.J. Pei, hep-ph/9610329 More advanced: Thermal model

  8. Significance of Feeddown Hadron Primordial Fraction  0.18 K 0.30 0 0.50 K* 0.60  1.00 f0(980) 1.00 p, 0.20 ++ 0.80 * 1.00 * 0.80

  9. Medium Effect in Dense Nuclear Matter • Brown-Rho Scaling • Rho Broadening • Low Mass Dilepton measuring  properties R. Rapp, et al Last Call for RHIC Predictions Nucl.Phys. A661 (1999) 205-260 • Chiral UA(1) symmetry restoration (J. Schaffner, D. Kharzeev, et al.)

  10. q l s  q l How to Probe Early Stage? Golden:   J/ • Modification in medium • Decay quicklymatter exists 10-23s • Small or no FSIleptons, photons, neutrino Small Branching Ratio(10-4), Low Production Rate

  11. f-Production: Hadronic versus Leptonic Decay Channel • Different decay channels: • NA49: F K-K+ • NA50: F -+ • Transverse momentum spectrum • fit: 1/mTdn/dmT ~ exp(-mT/T) (NA49: 3.0<y<3.8) significant differences in slopes and yields Dieter Röhrich, QM02

  12. K l+l- K  K+K-  c=50fm AMPT, STAR Nucl-th/0202086  Vector Meson at RHIC 130GeV • AMPT: (l+l-)/(K+K-)=1.5 • Experiments’ comparison

  13. PHENIX Preliminary PHENIX Preliminary fKK fee  hadronic/leptonic decay 200GeV K+K- Sensitivity Reach e+e- J. Nagle, QM02

  14. Dileptons at SPS • Conventional cocktail of particles • Underpredicts dilepton production • Mass shifted??

  15. Cleaner Way of Detecting Modification? Hadronic Decay at Late Stage • Lower Density • Lower Temperature • Smaller Effect • Hadronic Decay • Larger Signal • Extrapolation Last Call for RHIC Predictions Nucl.Phys. A661 (1999) 205-260

  16. + - Invariant Mass Distribution from Data at QM2002 pp AuAu 40% to 80% STAR Preliminary STAR Preliminary sNN = 200 GeV 0.2  pT  0.8 GeV/c |y|  0.5 0 f0K0S  K*0 0 f0 K0S  K*0 0.2  pT  0.9 GeV/c |y|  0.5 Statistical error only Statistical error only • 2.1106 Au+Au minimum biasevents and 4.7106 pp events • Breit-Wigner  fixed width 0  = 150 MeV and f0  = 75 MeV  fixedf0 masse  0.98 GeV (AuAu) and 0.96 GeV (pp) • 0 mass = 0.698 ± 0.013 GeV (AuAu) • 0 mass = 0.729 ± 0.006 GeV (pp) New: pT dependence P. Fachinia (STAR)

  17. STAR Preliminary K*0 Mass and Width Distribution K*0 Mass shift in p+p and Au+Au at low pT possible in-medium dynamic effect modified K*0 mass and the line shape K*0 width matches the MC prediction H. Zhang (STAR)

  18. What Effects? • Rescattering • Phase Space • Interference • Modification Ron Longacre, et al Work in progress

  19. Probe Freeze-out Dynamics Strange Hadron Resonances as a signature of freeze-out dynamics hep-ph/0103149 Basic Idea:: Two parameters two measurements:   e-m/T Surviving possibilityThermal factor   e-t/c

  20. Difference (t) may be Small Effect is Large RHIC Initial Production Final Production Transport ModelUrQMD SPS M. Bleicher QM02

  21. K*  K K* K* measured K* lost  K K*   K* K K K K* measured Kinetic freeze-out Chemical freeze-out All that Matters: X-section Different by 5 Rescattering>Regeneration at later stage

  22. K*0/K in AuAu is a factor of 2 lower than in STAR pp  rescattering STAR Preliminary Yield and pT Spectra STAR Preliminary H. Zhang (STAR) J. Ma (STAR)

  23. Flow/pQCD Effect Gyulassy, etc. Leading Quark Effect

  24. T=156MeV pp: 63GeV ISR Vector Mesons STAR Preliminary Particle Spectra

  25.  In AuAu Preliminary  In pp Preliminary STAR Preliminary mT-m0 Power Law Spectra Power lawmT Exponential

  26. What Puzzles? At pT ~ 2-3 GeV/c, yields approach each other. Heavier mass particles show stronger collective flow effects ! ? When did the collectivity developed at RHIC

  27. 130GeV Spectra Meet at 2GeV/c 2GeV/c PUZZLE? dN/(dypTdpT)=constant |pT=2GeV/c f,  different (rare particles) Low production Cross section Small Scattering X-section Less flow from hadronic stage??? Proton Puzzle???

  28. <pT> centrality dependence 1)p, K, p mean transverse momentum <pT> increase in more central collisions; 2) Heavier mass particle <pT> increase faster than lighter ones as expected from hydro type collective flow; 1)p, K, p mean transverse momentum <pT> increase in more central collisions; 2) Heavier mass particle <pT> increase faster than lighter ones as expected from hydro type collective flow; 3)f-meson seems flow differently. Star preliminary J. Ma (STAR)

  29. Y   K y py K* Y K X K K* Px x K* K* X Momentum phase space Coordinate phase space Resonance Elliptic Flow v2 Coordinate-space-anisotropy  Momentum-space-anisotropy K Nuclei Non-central Collisions  Hot System Elliptic Shape  (A.M.Poskanzer and S.A.Voloshin, Phys. Rev. C 58, 1671 (1998)) •  partonic flow? • Daughters re-scattering  K*0 • v2 sensitive to coordinate phase space

  30. K*0 ,  Elliptic Flow v2 STAR Preliminary Statistical error only Statistical error only • Observed Significant K*0,  Elliptic Flow v2 vs. Centrality and pT • Need more statitics

  31. Summary • Resonances are Important Tools in Heavy Ion Physics • Particle Production • Matter Properties (particle properties) • Hadronic Decay Probes Freeze-out Dynamics • Flow/High pT Effect

  32. More Conventional Approach CERES J. Kapusta QM02 Hadronic channels consistent??

  33. Hadronic Decay Mode

  34. Statistical models T. Ullrich QM02 Statistical Model: Work Reasonably well More Resonance Data Coming Dieter Röhrich, QM02

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