Identified Hadrons from  sNN = 130 GeV Au-Au collisions measured in PHENIX

1. Identified Hadrons from sNN = 130 GeV Au-Au collisions measured in PHENIX Julia Velkovska (BNL) for PHENIX • Identified hadronmeasurements in PHENIX • Identified charged hadrons via TOF • Neutral pions using EMC • Results • Transverse momentum spectra (identified charged hadrons) • <pT> and dN/dy as a function of Npart • Combine with p0 measurement - > ratios at high pT for 10% central • Decomposition of the charged hadron spectra to mesons and baryons • Conclusions and outlook ICPAQGP2001, Jaipur Julia Velkovska

2. Identified charged hadrons Tracking system: Drift Chamber , PC1 dp/p = 0.6% + 3.5% p (GeV/c) Timing system: BBC - start TOF - stop s = 115 ps Acceptance: D f = 45 deg D h = 0.7 PID : momentum dependent bands in mass2 ICPAQGP2001, Jaipur Julia Velkovska

3. Neutral pion measurement Two analyses with very different systematics • pair measurement (yields from invariant mass distributions) • yields extracted statistically – large combinatorial background • requires many events • difficult at low pT • signal to background improves at higher pT PbGl PbSc ICPAQGP2001, Jaipur Julia Velkovska

4. Identified charged hadron spectra • Intergrate the spectra to obtain <pT> and dN/dy • Use the data where measured • Extrapolate to 0 and to œ • with several different functions • Extrapolation fractions: • 30+/-6% for p+/- • 40+/-8% for K+/- • 25+/-7.5% for p and pbar ICPAQGP2001, Jaipur Julia Velkovska

5. Mean transverse momentum • Mean pt growing with Npart and mass - consistent with flow • (Anti)proton <pT> significant increase from pp collisions • The same relative increase from peripheral to central for all particles 20+/- 5 % increase 20+/- 5 % increase ICPAQGP2001, Jaipur Julia Velkovska

6. Centrality dependence of hadron yields per participant • Excellent agreement between published charged multiplicities and identified hadron multiplicities! • Is the increase in dNch/dh / (0.5 Np)due to hard processes ? • How do the different particle species contribute to the total yield ? ICPAQGP2001, Jaipur Julia Velkovska

7. Centrality dependence of identified charged hadron yields • (Anti)proton yields per participant pair rise faster than pion yields with Npart ! • Similar behavior in K+ , K-, p and p • Different from AGS and SPS Pb-Pb 21% +/- 6% (stat) +/- 8%(syst) 94%+/-11%(stat)+/-26%(syst) for K+ 66%+/-12%(stat)+/-20%(syst) for K- 72% +/- 9 % (stat) +/- 20%(syst) ICPAQGP2001, Jaipur Julia Velkovska

8. Centrality dependence of identified hadron ratios • Kaon, proton and anti-proton • yields rise faster than the pions. • Significant fraction of the charged • multiplicity increase with centrality • is due to kaons and baryons ! • Proton/kaon and anti-proton/kaon • ratios flat within errors • Anti-proton production follows • strangeness production ICPAQGP2001, Jaipur Julia Velkovska

9. Identified charged hadron spectra ICPAQGP2001, Jaipur Julia Velkovska

10. Hydro + cascade or baryon junctions + pQCD ? D. Teaney et.al. Hydro+cascade 5% central I.Vitev et.al. Baryon junctions+pQCD ICPAQGP2001, Jaipur Julia Velkovska

11. Identified hadron spectra in central Au-Au collisions Excellent agreement between charged and neutral pions ! (anti)proton – pion crossing confirmed! ICPAQGP2001, Jaipur Julia Velkovska

12. Nucleon to Pion Ratios p/p+and p/p0rising with pT p/p-and p/p0rising or saturating at high pT Different from pp collisions - (anti)protons don’t come from jets ICPAQGP2001, Jaipur Julia Velkovska

13. X.N.Wang Anti-proton /proton ratio in Central Au-Au Collisions Hydro predicts a flat line pQCD – pbar/p is falling as a function of pT flat or falling? Not enough statistics in year 2000 run PHENIX has x 200 more statistics on tape from year 2001 run ICPAQGP2001, Jaipur Julia Velkovska

14. Hadron suppression at high pT high pT hadron suppression different suppression for h and p0 ICPAQGP2001, Jaipur Julia Velkovska

15. Decomposing the hadron spectra to mesons and nucleons • Subtract anti-protons and protons from charged hadrons • Compare the meson spectrum to p0 Difference in high pT charged hadron And p0 suppression primarily due to nucleons ICPAQGP2001, Jaipur Julia Velkovska

16. Conclusions • PHENIX has measured identified hadrons over a broad momentum range • Internal consistency: • Identified charged and neutral pions • Charged and identified charged spectra • Charged multiplicity and identified hadron multiplicity • Protons dominate over pions at high pt in central collisions • p/p ratio rising with pt , approaching 1 and suggestive for saturating behavior – more statistics needed • Mean pT increases with Npart similarly for all particle species • dN/dy per participant pair rises faster for kaons, protons and anti-protons than for pions • Hadron suppression at high pt • Different high pt behavior for mesons and baryons ICPAQGP2001, Jaipur Julia Velkovska

17. Outlook - Year 2 Run Present run started July 2001 > 60M Au + Au min bias events collected p + p run just starting New detectors for hadron measurement: • 8 complete sectors of EMCAL (6 PbSc, 2 PbGl) • PC2 and PC3 on West arm • Rebuilt drift chamber • Upgraded trigger • Charged hadrons and p0 pT > 10 GeV/c • High pT behavior of p-/p and p-/p ratios both in Au-Au and pp with high statistics and as a function of centrality • Study centrality dependence of hadron production with finer binning ICPAQGP2001, Jaipur Julia Velkovska

18. Extra slides ICPAQGP2001, Jaipur Julia Velkovska

19. Zero Degree Calorimeters (ZDC) - sensitive to spectator neutrons BBC – charged particlies form the collision zone Good min bias trigger –measured 92+/-4 % of the total geom cross-section Using a combination of the ZDC’s and BBC’s we can define centrality classes. Glauber model to determine Npart ZDC 15-30% 30-60% 0 - 5 % 60-92 % 5–15 % Measuring Collision Centrality BBC ICPAQGP2001, Jaipur Julia Velkovska

20. Identified charged hadron spectra In central collisions: at pT ~ 2GeV/c anti-proton yields comparable to pion yields Protons cross the pions ~ 1.6 GeV/c peripheral mid - central ICPAQGP2001, Jaipur Julia Velkovska

21. Charged hadrons • single particles, no combinatorial background • better per-event statistics, need fewer events for same pT range • momentum reconstruction increasingly difficult with higher pT Drift Chamber PC1: tracking PC3 - used to cut background ICPAQGP2001, Jaipur Julia Velkovska

22. ICPAQGP2001, Jaipur Julia Velkovska

23. What about mT scaling ? ICPAQGP2001, Jaipur Julia Velkovska