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Global observables in the PHENIX experiment

Global observables in the PHENIX experiment. Transverse Dynamics at RHIC BNL, March 6-8, 2003. David Silvermyr, LANL for the PHENIX Collaboration. E T and N ch at midrapidity Measurement technique Centrality selection Centrality dependence s NN dependence

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Global observables in the PHENIX experiment

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  1. Global observables in the PHENIX experiment Transverse Dynamics at RHIC BNL, March 6-8, 2003 David Silvermyr, LANL for the PHENIX Collaboration

  2. ET and Nch at midrapidity • Measurement technique • Centrality selection • Centrality dependence • sNN dependence Something new since QM02 and afterwards: • More peripheral collisions at sNN=130 and 200 GeV included • sNN= 19.6 GeV results • More theoretical model comparisons Outline

  3. Global Observables “Spectators” Impact Parameter “Participants” “Spectators” Centrality defined as percentile of tot Npart , Ncoll , b thru Glauber model • WHAT ? * dNch/d, dET/d * Reflect conditions well after freeze-out and resonance decays • WHY ? * “Easy” measurements * Characterize collision geometry * Constrain models * Initial conditions

  4. Charged Multiplicity • Pad Chambers: • RPC1 = 2.5 m • RPC3 = 5.0 m • ||<0.35, = • Transverse Energy • Lead-Scintillator EMCal: • REMC = 5.0 m • ||<0.38,  = (5/8) • Trigger • Beam-Beam Counters: 3.0<|h|<3.9, = 2 • Zero-Degree Calorimeters: • |h| > 6, |Z|=18.25 m PHENIX Setup, Year-2

  5. B=0 Count tracks on a statistical basis (no explicit track reconstruction) • Combine all hits in PC3 with all hits in PC1. • Project resulting lines onto a plane through the beam line. • Count tracks within a given radius. • Determine combinatorial background by event mixing technique Charged Multiplicity Measurements

  6. EMCal absolute energy calibration • MIP peak • E/p matching peak for e • 0 mass peak • Convention: • Ei= Eitot - mN for baryons • Ei= Eitot + mN for antibaryons • Ei= Eitot for others Transverse Energy Measurements • EMCal is “almost” hadronic calorimeter: • EEMC= 1.0 * Etotfor , 0 • EEMC= 0.7 * Etotfor  0 • EEMC ET transformation: • ET= 1.23 * EEMC

  7. ZDC vs BBC Define centrality classes: ZDC vs BBC Extract N participants: Glauber model Centrality Selection ET EZDC b QBBC Nch PHENIX preliminary Nch PHENIX preliminary ET

  8. ET and Nch exhibit consistent behavior at sNN=130 GeV and 200 GeV ET @130 GeV ET @200 GeV Centrality dependence PHENIX preliminary • Stat. errors • Negligible • Syst. errors • Band: possible common tilt • Bars: total syst. error Nch @130 GeV Nch @200 GeV PHENIX preliminary

  9. For the most central collisions: 200 GeV / 130 GeV PHENIX preliminary • Constant scaling from central to semi-peripheral collisions • Drop in peripheral collisions (Npart70) ? PHENIX preliminary

  10. PHENIX preliminary <ET> / <Nch> PHENIX preliminary Weak dependence from centrality Weak (no) dependence from energy

  11. 19.6 GeV data: • centrality determination not yet finalized, coming soon… • ET/Nch is not effected by this error (same centrality classes) <ET> / <Nch> + 19.6 GeV results PHENIX preliminary PHENIX preliminary RHIC point at SPS energy:

  12. 130 GeV 200 GeV HIJING X.N.Wang and M.Gyulassy, PRL 86, 3498 (2001) Mini-jet S.Li and X.W.Wang Phys.Lett.B527:85-91 (2002) EKRT K.J.Eskola et al, Nucl Phys. B570, 379 and Phys.Lett. B 497, 39 (2001) KLN D.Kharzeev and M. Nardi, Phys.Lett. B503, 121 (2001) D.Kharzeev and E.Levin, Phys.Lett. B523, 79 (2001) PHENIX preliminary Nch: Comparison to theory • Mini-jet and KLN: describe data well • HIJING: not too bad

  13. 200GeV/130GeV PHENIX preliminary Nch: Comparison to theory pp point  • HIJING is also out of the game • Npart70 limit for KLN (gluon saturation) model application?

  14. AMPT (multiphase transport model) B.Zhang et al, Phys.Rev.C 61, 067901 (2000); nucl-th/0011059 String fusion model N.Armesto et al, Phys.Lett. B527, 92 (2002) N.S.Amelin et al, Eur.Phys.J C22, 149 (2001) Semi-Hard Scattering A. Accardi, Phys.Rev.C64:064905,2001 Dual String Model R. Ugoccioni et al., Phys.Lett.B491:253-256,2000 130 GeV 200 GeV Nch: More models 200/130 Not too bad… And what about ET?

  15. 130 GeV 200 GeV String fusion model: overestimate ET AMPT seems to overestimate the R(200/130) Hijing 1.37, Hijing BbarB 1.0 with quenching and shadowing: Overestimates R(200/130), for central collisions. ET: Comparison to theory 200/130

  16. Energy density (Bjorken): 2% most central at sNN=200 GeV: •   5.5 GeV/fm3 • Considerably bigger than critical  1GeV/fm3 From AGS, SPS to RHIC: Transverse energy and charged particle multiplicity densities per participant consistent with logarithmic behaviour PHENIX preliminary Energy Dependence PHENIX preliminary 19 GeV points coming soon

  17. Centrality dependence of dNch /dh and dET /dh have been measured at ÖsNN = 130 GeV and 200 GeV in Au+Au collisions; ÖsNN = 19.6 GeV results coming • Both dNch /dh and dEt /dh per participant increase with centrality: • the increase is stronger than at SPS • Nch data well described by KLN and Mini-jet model predictions • Room for improvement regarding theory description for ET • The ratio R(200/130) consistent with constant scaling vs centrality from central to semi-peripheral collisions and drops at Npart<70 • Sets the peripheral limit of gluon saturation (KLN) model application • <dET >/<dNch> measured at ÖsNN = 19, 130 and 200 GeV • Weak dependence on centrality • Decreased 20% from ÖsNN = 200 to 19.6 GeV • d - Au (at ÖsNN = 200 GeV) results coming soon… Summary

  18. The PHENIX Collaboration A strongly international venture: • 11 nations Brazil, China, France, Germany, India, Israel, Japan, South Korea, Russia, Sweden, United States • 51 institutions

  19. Fit: dX/d  Npart: • CERES (sNN=8.7 GeV) • dNch/d: =1.09 • WA98 (sNN=17.2 GeV) • dNch/d: =1.070.04 • dET/d: =1.080.06 • PHENIX (sNN=130 GeV) • dNch/d: =1.180.05 • dET/d: =1.160.05 • PHENIX (sNN=200 GeV) • dNch/d: =1.200.05 • dET/d: =1.170.05 PHENIX preliminary Backup: Centrality dependence vs sNN PHENIX preliminary Not yet fair comparison of dX/d in C.M. and Lab. systems

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