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J. Burward-Hoy Department of Physics and Astronomy, University at Stony Brook, New York

Transverse Momentum Spectra of Identified Hadrons in s = 130 GeV Au-Au Collisions. J. Burward-Hoy Department of Physics and Astronomy, University at Stony Brook, New York for the PHENIX Collaboration Outline of Topics Motivation Identifying   , K  , p  in PHENIX

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J. Burward-Hoy Department of Physics and Astronomy, University at Stony Brook, New York

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  1. Transverse Momentum Spectra of Identified Hadrons in s = 130 GeV Au-Au Collisions • J. Burward-Hoy • Department of Physics and Astronomy, University at Stony Brook, New York • for the PHENIX Collaboration • Outline of Topics • Motivation • Identifying , K, p in PHENIX • Single Particle Pt spectra • Radial flow • hydrodynamics-based parameterization • Discussion and conclusion The PHENIX Experiment J. Burward-Hoy

  2. Motivation RHIC: Ecm = 130 GeV Au on Au collisions • low pt: soft processes • multiple hadronic rescattering • hydrodynamic behavior , K, p, anti-p carry most of energy collectively flow at t decouple at Tfo • high pt: hard processes • hard scattering, jets • pQCD The PHENIX Experiment J. Burward-Hoy

  3. Detecting , K, p in PHENIX r z  ~ q/p y r 0 x DC main bend plane DC resolution p/p ~ 1%  3.5% p TOF resolution 115 ps pt = p sin(0) PC1 and Event vertex polar angle The PHENIX Experiment J. Burward-Hoy

  4. Corrections to the Raw Spectra Used MC single particles and track embedding to correct for Tracking inefficiencies and momentum resolution Geometrical acceptance Decays in flight (’s and K’s) Correction is p and PID dependent Particle Acceptance 0.2 GeV/c -0.35 <  < 0.35 The PHENIX Experiment J. Burward-Hoy

  5. pt Spectra of Identified Hadrons The PHENIX Experiment J. Burward-Hoy

  6. HIJING  K p pt (GeV/c) Protons Cross the Pions? p crosses  p crosses K The PHENIX Experiment J. Burward-Hoy

  7. Centrality selected pt spectra. . . The PHENIX Experiment J. Burward-Hoy

  8. <pt> Across Participant Number The PHENIX Experiment J. Burward-Hoy

  9. In the range mt - m0 < 1 GeV, fit and extract the inverse slope Teff Identified particle mt-m0 Spectra If static thermal source, then spectra are parallel The PHENIX Experiment J. Burward-Hoy

  10. HIJING Effective Temperature and HIJING No radial flow in HIJING HIJING To measure the expansion parameters, use hydrodynamics-based parameterization. . . The PHENIX Experiment J. Burward-Hoy

  11. parameters normalization A freeze-out temperature Tfo surface velocity t 1/mt dN/dmt A Tfo t() mt f()   1 Hydrodynamics-based parameterization 1/mt dN/dmt = A  f()  d mT K1( mT /Tfo cosh  ) I0( pT /Tfo sinh  ) t integration variable   radius r = r/R definite integral from 0 to 1 particle density distribution f() ~ const linear velocity profile t() = t surf. velocity t ave. velocity <t > = 2/3 t boost () = atanh( t() ) minimize contributions from hard processes fit mt-m0<1 GeV The PHENIX Experiment J. Burward-Hoy

  12. PHENIX Preliminary PHENIX Preliminary 5% central data Tfo ~ 104  21 MeV t ~ 0.7  0.1 < t > ~ 0.5  0.1 Systematic errors estimated ~8% in Tfo ~5% in t Arrows indicate upper pt in fit PHENIX Preliminary The PHENIX Experiment J. Burward-Hoy

  13. PHENIX Preliminary PHENIX Preliminary 3 2/NDF 102 2 10 1 1 Parameter Space: 2 Contours of -K-p 5% central The PHENIX Experiment J. Burward-Hoy

  14. Overlap Region in Parameter Space 2 contour overlap Tfo ~ 125 - 83 MeV ~ 104 MeV t ~ 0.6 - 0.8 ~ 0.7 < t> ~ 0.4 - 0.6 ~ 0.5 CERN Pb-Pb NA49: T ~ 132 - 108 MeV ~ 120 MeV t ~ 0.43 - 0.67 ~ 0.55 Systematic errors estimated ~8% Tfo ~5% t The PHENIX Experiment J. Burward-Hoy

  15. The H2H Model Comparison (Hydro 2 Hadrons)D. Teaney, E. Shuryak, et. al. flowing hadronic fluid AND particle cascade uses Hydrodynamics + Relativistic Quantum Molecular Dynamics (RQMD) cascade more constrained  predictive power no scaling of nucleons to match data 0 ~ 16.75 GeV/fm30 ~ 1.0 fm/c p/p ~ 0.5 <0> ~ 10.95 GeV/fm3 , K Tfo ~ 135 MeV <t > ~ 0.55 nucleons ~ 120 MeV <t > ~ 0.6 5% central NOTE: includes weak decays The PHENIX Experiment J. Burward-Hoy

  16. Conclusions • Fully normalized, centrality selected , K, p/pbar spectra in 130 GeV Au-Au collisions are measured in PHENIX (Summer 2000 runs) significant p and pbar contribution to hadron spectra starting at ~ 2 GeV/c STAR and PHENIX pbar consistent • Both Teff and <pt> depend on Npart. Teff depends on m0 for 5% central and minimum bias events. There seems to be less of a dependence in the 60 - 92% centrality. • The data suggest sizeable radial flow at RHIC A simple model that assumes hydrodynamic behavior is fit simultaneously to the 5% central data. Good 2 fits for a finite range of anti-correlated parameters Tfo ~ 125 - 83 MeV (~ 8% syst.) t ~ 0.6 - 0.8 ( ~ 5% syst.) < t> ~ 0.4 - 0.6 • In comparison to NA49: Tfo ~ 132 - 108 MeV t ~ 0.43 - 0.67 • H2H model (D. Teaney, E. Shuryak, et. al) , K: Tfo ~ 135 MeV <t >~ 0.55 nucleons: Tfo ~ 120 MeV <t >~ 0.6 • Reduce 20% systematic uncertainty in overall normalization. The PHENIX Experiment J. Burward-Hoy

  17. The mass-squared width: how particle identification is done. momentum p pathlength L m = p/ where  = L/ct time-of-flight t |mmeas2 - mcent2| < 2m22 Momentum resolution Time-of-Flight resolution H. Hamagaki The PHENIX Experiment J. Burward-Hoy

  18. 25-30% Centrality Collisions Participants 20-25% 0-5% 945  15% 347  15% 15-20% 10-15% 5-15% 673  15% 271  15% 5-10% 15-30% 383  15% 178  15% 0-5% 30-60% 123  15% 76  15% 60-80% 19  60% 19  60% 80-92% 3.7  60% 5  60% Event centrality: how “head-on” is the collision? The fraction of energy deposited in the Zero-degree Calorimeters. A. Denisov The fraction of counts in the Beam-beam Counters. The PHENIX Experiment J. Burward-Hoy

  19. D. Teaney   + + p H2H ModelThe Effect of Weak Decays K0s  + + -   - + p The measured contribution to nucleon spectra from such “real” background is forthcoming. The PHENIX Experiment J. Burward-Hoy

  20. (No QGP phase transition) t() 20 fm/c 2 fm/c  5 fm/c From Hydrodynamics:Radial Flow Velocity Profiles Velocity profile at  ~ 20 fm/c “freeze-out” hypersurface At each “snapshot” in time during the expansion, there is a distribution of velocities that vary with the radial position r Plot courtesy of P. Kolb The PHENIX Experiment J. Burward-Hoy

  21. Centrality Positive Negative Tfo <t> Tfo <t> min. bias 16112 0.390.07 15115 0.410.07 5% 15913 0.390.07 14917 0.460.1 60-92% 14312 0.280.1 13416 0.280.1 Effective Temperature and Linear Fit Teff = Tfo + m0 <t>2 5% central Tfo ~ 132 - 166 MeV <t> ~ 0.4 - 0.6 Systematic errors included Compared to hydrodynamics-based parameterization: Tfo within 30% and <t> within 6% The PHENIX Experiment J. Burward-Hoy

  22. 2 (Tfo,t) Contours PHENIX Preliminary PHENIX Preliminary  positive negative PHENIX Preliminary PHENIX Preliminary K PHENIX Preliminary PHENIX Preliminary p The PHENIX Experiment J. Burward-Hoy

  23. The PHENIX Detector -0.35 <  < 0.35 4.5M min. bias events The PHENIX Experiment J. Burward-Hoy

  24. Relevant CERN SPS Observables Teff = Tfo + m<t>2 Teff depends on m0 radial flow Tfo A + A p + A < t> • Bjorken’s formula: • initial energy density • <0> ~ 1/R20 dEt/dy • <0> ~ 3 GeV/fm3 (NA49) System Size = A1 A2 The PHENIX Experiment J. Burward-Hoy

  25. CERN SPSHydrodynamics-Based Parameterization The spectra are well described using hydrodynamic assumptions. CERN Pb-Pb NA49: T ~ 132 - 108 MeV ~ 120 MeV t ~ 0.43 - 0.67 ~ 0.55 The PHENIX Experiment J. Burward-Hoy

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