1. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Identified Charged Single Particle Spectra at RHIC-PHENIX Tatsuya Chujo (BNL) for the PHENIX Collaboration

2. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Physics of Identified Hadron Spectrum From identified single particle spectra, Hydro-dynamical collective expansion velocity ( . Thermal freeze-out temperature (T th ). Chemical freeze-out temperature and chemical potential (T ch,  B,  s ) Jet quenching effect at high p T by parton energy loss in medium (dE/dx). Inverse slope dN/dy High p T spectra Shed light on QGP formation at RHIC In this talk, we present identified (charged) single particle spectra as a function of centrality, measured at RHIC-PHENIX.

3. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. PHENIX Detector Setup Beam-Beam Counter (BBC) z-vertex, start timing for TOF Time-of-Flight (TOF) stop timing measurement Drift Chamber (Dch) momentum, flight path length Pad Chamber 1 (PC1) additional track z-information to Dch In this analysis, we use

4. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Particle Identification by TOF * Fitted  + region TOF - TOF expected Demonstrated Clear PID by TOF Time-of-Flight resolution  TOF ~ 110-120 ps

5. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. PID Cut Criteria Proton K+K+ ++ m 2 [(GeV/c 2 ) 2 ] Charge * Momentum [GeV/c] P K+K+ K-K- ++ -- p All momentum (a.u.)  : 0.1 < p < 2.0 GeV/c K : 0.2 < p < 2.0 GeV/c p/pbar : 0.2 < p < 4.0 GeV/c w/o PID cut PID by m 2 vs. momentum space |m 2 measured - m 2 0 | < 2.5  m 2 Momentum cutoff

6. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Correction factor for raw spectra  K p Pt [GeV/c] positive negative 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Based on single particle Monte Carlo simulation. Included overall effects 1.Tracking efficiency 2.Geometrical acceptance 3.Multiple scattering 4.Decay in flight 5.Hadronic int. 6.Dead area of detectors Confirmed that the multiplicity dep. is small by track embedding method in real data.

7. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Centrality Classes Dch raw multiplicity distributions CentralityParticipants 0-5% 347  15% 5-15% 271  15% 15-30% 178  15% 30-60% 76  15% 60-80% 19  60% 80-92% 5  60% Used correlation between BBC charge and ZDC energy to define centrality. Extracted N part based on Glauber model

8. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Results : Minimum bias p T spectra PHENIX Preliminary (a.u.) particlep T range  0.3 - 1.8 GeV/c K0.5 - 1.6 GeV/c proton0.5 - 3.0 GeV/c pbar0.8 - 3.0 GeV/c pions yield ~ proton and pbar yield @ p T ~ 2 GeV/c Large proton and anti-proton contributions at high p T.

9. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Minimum bias M T spectra PHENIX Preliminary (X 10 -1 ) (a.u.) In 0.2 < m t – m 0 < 1.2 [GeV/c 2 ], spectra for all species scale by single exp. function. Similar inverse slope for  and K. T proton > T    ~ 205  5 (stat.)  15 (sys.) MeV K  ~ 215  5 (stat.)  20 (sys.) MeV p, ~ 320  10 (stat.)  20 (sys.) MeV p Fitting results by single exp. function

10. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Centrality Dependence of M T Spectra for pions + + 0-5 % 5-15% 15-30% 30-60% 60-80% PHENIX Preliminary (a.u.) -- PHENIX Preliminary (a.u.) Single exponential scaling at 0.2 -1.0 GeV in m t -m 0. Almost parallel among all centrality classes. T  (central 0-5%) ~ 210 MeV  5 (stat.)  15 (sys.) MeV

11. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Centrality Dependence of M T Spectra for kaons K+K+ 0-5 % 5-15% 15-30% 30-60% PHENIX Preliminary (a.u.) K-K- PHENIX Preliminary (a.u.) Single exponential scaling at 0.2 -1.0 GeV in m t -m 0. Parallel slope among all centrality classes. T K (central 0-5%) ~ 217 MeV  5 (stat.)  20 (sys.) MeV.  T 

12. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Centrality Dependence of M T Spectra for p/pbar proton 0-5 % 5-15% 15-30% 30-60% 60-80% PHENIX Preliminary (a.u. ) p PHENIX Preliminary (a.u.) Single exponential scaling at 0.2 -1.2 GeV in m t -m 0. Gradual increase from centrality 60-80% to 30-60%. T proton (central 0-5%) ~ 325 MeV  17 (stat.)  20 (sys.) MeV > T .

13. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Centrality dependence of T PHENIX Preliminary Weak centrality dependence for T  and T K. Gradual rise of T proton and T pbar from peripheral to mid-central collisions. T   T K < T proton

14. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Mass Dependence of T PHENIX Preliminary Intuitive explanation of mass dependence of T  t : Transverse expansion velocity

15. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Comparison with CERN Energy PHENIX Preliminary The slopes of pions and protons at RHIC are higher than that of Pb+Pb collisions at SPS. Kaon’s slope is almost same at SPS Pb+Pb. SPS data : NA44 (most central)

16. BNL/ Tatsuya CHUJO 02/14/2001 @ CNS workshop, Tokyo Univ. Conclusions Single particle spectra for  , K , protons and anti-protons in each centrality class are studied. In p T spectra, a large proton and anti-proton contributions at high p T. Weak centrality dependence of slopes for T  and T K. Gradual rise of T proton and T pbar from peripheral to mid-central collisions. T   T K < T proton at all centrality classes. The slope of pions and protons at RHIC are higher than that of Pb+Pb collisions at SPS. Kaon’s slope at RHIC is almost same at SPS Pb+Pb.