Nov2,2001High P T Workshop, BNL Julia Velkovska High pt Hadrons from  sNN = 130 GeV Au-Au collisions measured in PHENIX Julia Velkovska (BNL) for PHENIX High p T measurements in PHENIX –Identified protons and anti-protons – 3.5 GeV/c –Neutral pion analysis – up to 4 GeV/c –Charged hadron analysis - up to 5 GeV/c Results –Transverse momentum spectra (identified charged hadrons) – and dN/dy as a function of N part –Combine with  0 measurement - > ratios at high p T for 10% central –Decomposition of the charged hadron spectra to mesons and baryons Conclusions and outlook

Nov2,2001High P T Workshop, BNL Julia Velkovska Identified charged hadrons Tracking system: Drift Chamber, PC1  p/p = 0.6% + 3.5% p (GeV/c) Timing system: BBC - start TOF - stop  = 115 ps Acceptance:  deg  PID : momentum dependent bands in mass 2

Nov2,2001High P T Workshop, BNL Julia Velkovska 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 p T signal to background improves at higher p T Neutral pion measurement PbSc PbGl

Nov2,2001High P T Workshop, BNL Julia Velkovska Charged hadrons single particles, no combinatorial background better per-event statistics, need fewer events for same p T range momentum reconstruction increasingly difficult with higher p T Drift Chamber PC1: tracking PC3 - used to cut background

Nov2,2001High P T Workshop, BNL Julia Velkovska Measuring Collision Centrality  Zero Degree Calorimeters (ZDC) Sensitive to spectator neutrons  Using a combination of the ZDC’s and BBC’s we can define Centrality Classes % ZDC BBC %

Nov2,2001High P T Workshop, BNL Julia Velkovska Identified charged hadron spectra Central mid - centralperipheral

Nov2,2001High P T Workshop, BNL Julia Velkovska Hydro + cascade or baryon junctions + pQCD ? 5% central Hydro+cascade D. Teaney et.al. Baryon junctions + pQCD I.Vitev et.al. Both theories can describe the data up to 3 GeV/c

Nov2,2001High P T Workshop, BNL Julia Velkovska Mean transverse momentum Mean pt growing with N part and mass - consistent fith flow (Anti)proton significant increase from pp collisions The same relative increase from peripheral to central for all particles 20+/- 5 % increase

Nov2,2001High P T Workshop, BNL Julia Velkovska Yields as a function of N part Is the increase in dN ch /d  p )  due to hard processes ? How does the yield per participant behave for different particles ?

Nov2,2001High P T Workshop, BNL Julia Velkovska Identified charged hadron yields Anti-proton and proton yields per participant pair rise faster than pion yields with N part ! Different from SPS Pb-Pb 20 +/- 6% increase 65 +/- 7 % increase

Nov2,2001High P T Workshop, BNL Julia Velkovska Identified hadron spectra in central Au-Au collisions Excellent agreement between charged and neutral pions ! (anti)proton – pion crossing confirmed!

Nov2,2001High P T Workshop, BNL Julia Velkovska Nucleon to Pion Ratios p/    and p/    rising with p T p/    and p/    rising or saturating at high p T Different from pp collisions - (anti)protons don’t come from jets

Nov2,2001High P T Workshop, BNL Julia Velkovska Anti-proton /proton ratio in Central Au-Au Collisions flat or falling? Not enough statistics in year 2000 run PHENIX has x 10 more statistics on tape from year 2001 run

Nov2,2001High P T Workshop, BNL Julia Velkovska p/p ratio falling with p T –Jet quenching moves the p/p ratio below the pp value –PHENIX will measure pp collisions this year p/  ratio has a peak which changes with centrality hydrodynamics p/p ratio flat with p T p/  ratio steadily rising with p T Theory expectations: pQCD++

Nov2,2001High P T Workshop, BNL Julia Velkovska High density QCD expects m T scaling : The data are consistent with m T scaling up to 3.5 GeV.

Nov2,2001High P T Workshop, BNL Julia Velkovska Hadron suppression at high p T high p T hadron suppression different suppression for h and  

Nov2,2001High P T Workshop, BNL Julia Velkovska Decomposing the hadron spectra to mesons and nucleons Subtract anti-protons and protons from charged hadrons Compare the meson spectrum to  0 Difference in high p T charged hadron And  0 suppression primarily due to nucleons

Nov2,2001High P T Workshop, BNL Julia Velkovska We can measure it - can you predict it for  sNN = 200 GeV Au-Au collisions ? (Anti)proton / pion ratio as a function of p T for different centralities anti-proton / proton ratio as a function of p T for different centralities as a function of N part and mass dN/dy as a function of N part and mass High p T suppression for mesons and baryons All these taken together can help differentiate between different production mechanisms at high p T

Nov2,2001High P T Workshop, BNL Julia Velkovska PHENIX measured p,p,  0,h up to 3.5,4,5 GeV/c All measurements are internally consistent Protons dominate over pions at high p t in central collisions Mean p T increases with N part similarly for all particle species dN/dy per participant pair rises faster for (anti)protons than for pions p/  ratio rising with p t, approaching 1 and suggestive for saturating behavior – more statistics needed p/p ratio flat or falling at high p t - inconclusive due to low statistics Hadron suppression at high p t –Different high pt behavior for mesons and baryons Conclusions

Nov2,2001High P T Workshop, BNL Julia Velkovska Present run started July 2001 Hope to collect: ~ 300 mb -1 Au + Au ~ 3.5 pb -1 p + p Will be able to pin down the high p T behavior of p - /p and p - /  ratios both in Au-Au and pp New detectors: 8 complete sectors of EMCAL (6 PbSc, 2 PbGl) Rebuilt drift chamber Multiplicity vertex detector (MVD) South Muon Spectrometer Upgraded trigger Upgraded data aquisition Outlook - Year 2 Run