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Overview Of PHENIX Results Year2000 Run

Overview Of PHENIX Results Year2000 Run. Glenn R. Young (ORNL) for the PHENIX Collaboration DNP Meeting 10/4/2000. PHENIX Collaboration. Goals of PHENIX Experiment. Search for evidence of Quark-Gluon Plasma

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Overview Of PHENIX Results Year2000 Run

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  1. Overview Of PHENIX ResultsYear2000 Run Glenn R. Young (ORNL) for the PHENIX Collaboration DNP Meeting 10/4/2000

  2. PHENIX Collaboration PHENIX Collaboration October 2000 DNP meeting

  3. Goals of PHENIX Experiment • Search for evidence of Quark-Gluon Plasma • Cover broad range of timescales, from initial state and possible deconfined state thru expansion and cooling to final-state hadrons • Following range of probes to be covered • Vector mesons • Direct photons (real and virtual) • Identified hadrons • Collective motion and correlations • Global observables • Capability to cover A+A, p+A, p+p essential • Full range of energy densities • Establish baseline; claims for new behavior assessed against this • Study spin-structure of nucleon, spin asymmetries • Asymmetry for gluons • Flavor-tagged quark, antiquark spin structure • See JD2 (Saito), JD4 (Bunce), JD6 (Perdekamp), JD7(Xie), JD8 (Barish), JD9 (Goto) PHENIX Collaboration October 2000 DNP meeting

  4. Detector Concept • Detector is set of highly segmented spectrometers • Pair spectrometers essential for vector meson, virtual photon detection • Good particle identification (e,p,K,p,g,m plus pairs e.g. p0, w, f) • Low occupancy of “pixels” • Essential for particle identification, systematic control of efficiency • High data rate and selective multi-level triggering • Can examine all Au+Au collisions, even at 10*LDesign • Many signals involve one or more powers of aEM and/or heavy quarks • See BE5 (Deshpande), BE9 (Adler) • Two “central” arms • Electrons, photons, hadrons; Coverage: Df = p/2 each, Dh=0.7 • Two “muon” endcaps • Coverage: Df = 2p each, Dh=1.15-2.44 (north), 1.15-2.25 (south) • e/p, m/h rejections better than 10-3 PHENIX Collaboration October 2000 DNP meeting

  5. Isometric of PHENIX Detector PHENIX Collaboration October 2000 DNP meeting

  6. PHENIX for Year2000 Run • Items in red installed with electronics • Items in yellow installed, with electronics to follow for Year2001 run • North muon magnet installed, chambers in 2002 • South muon magnet in assembly area, operate in 2001 • ZeroDegreeCalorimeters located in RHIC tunnel, between “DX” beam-merging magnets • ZDCs placed to intercept neutrons emitted in beam direction at collision point ZDC ZDC PHENIX Collaboration October 2000 DNP meeting

  7. Central Arm Particle Identification PHENIX Collaboration October 2000 DNP meeting

  8. Run/Luminosity Progress In Year2000 • RHIC machine studies, experiment commissioning March thru June • First collisions June 15, 2000 • (g =30) + (g =30) operation • Initial operation at (g=70)+(g=70) with 6+6 bunches yielded 500,000 minimum-bias triggers • Final operation at (g=70)+(g=70) and 55+55 bunches yielded nearly 45,000,000 minimum-bias triggers, i.e. 4.1 mb-1 • Trigger does limit z-coordinate of accepted event vertices • Taped ~5M events • Polarized beam stored in one ring during September • Manipulated polarization • Preserved during acceleration! PHENIX Collaboration October 2000 DNP meeting

  9. Global Event Characteristics • Overview of conditions prevailing in collision; Check of participant-nucleon scaling • Sums over all times in collision • See DC1 (Greene), DC3 (Morrison) for general talks • Pair of Zero Degree Calorimeters form trigger for “softest” collisions • Beam-Beam counters • tag 95% of strong interactions • impose our chosen z-limits on diamond • provide time-zero • luminosity monitor • see DC9 (Ohnishi) • EMCalorimeter measures energy deposited • Pad Chambers and Drift Chamber • count, track charged particles • see DC11 (ElChenawi/Sivertz), JC11 (Butsyk) PHENIX Collaboration October 2000 DNP meeting

  10. ZeroDegreeCalorimeter Energy Spectra • Relativistically-contracted electric field of one Au nuclei can photo-eject neutrons from other • Resulting mutual Coulomb-dissociation s = 3.7 barns • Single-neutron, two-neutron peaks self-calibrate ZDC • Luminosity measurement • RHIC beam-tuning (!!!) • See JC8 (White), JC9 (Ewell) PHENIX Collaboration October 2000 DNP meeting

  11. Counting Participants • ZDC provides a means to order collisions by centrality, given a means to break the 2-fold ambiguity for low/no energy in ZDC: no vs. violent collison • Beam-beam counter multiplicity, EMCalorimeter energy, or charged-particle multiplicity all serve to do this • ZDC vs. BB pulseheights has expected monotonic behavior in each “branch” • Glauber model reproduces ZDC spectrum reasonably • May estimate # of participant nucleons based on this method • tie to AGS, SPS data PHENIX Preliminary PHENIX Collaboration October 2000 DNP meeting

  12. Vertex Cuts for Multiplicity, ET • RHIC ran only 28 MHz “accelerating” RF this year • Results in s = 50-70 cm diamond • Vertex can be restricted by Beam-Beam Dt time cut or Pad Chamber vertex cut using 3-D space points (left side) • EMCal energy vs. calorimeter z-position • Example shown for events near magnet poletip • Shows need to select events which have clear view of Interaction Diamond PHENIX Collaboration October 2000 DNP meeting

  13. Multiplicity Distribution PHENIX Preliminary • Pad Chamber has 2 layers, separated radially by 2 meters • Each provides 3D space points, sx = 2-3 mm • Correlation analysis yields event charged-particle multiplicity • Histogram shows yield as function of dNcp/dh, at h=0, normalized to Df=2p, for sqrt(s)=130 GeVA Au+Au • Mean multiplicity for 6% most central events is 540 +-10% • SPS result is 400 for sqrt(s)=17.2 GeVA Pb+Pb; ~35% higher at RHIC PHENIX Collaboration October 2000 DNP meeting

  14. Multiplicity Distribution (cont.) PHENIX Preliminary • Drift Chamber hits can also be analyzed stand-alone to determine charged-particle multiplicity see JC5 (Averbeck) • Glauber analysis applied to dNcp/dh, at h=0, as well as to EMCal and ZDC energy spectra • These analyses imply Nparticipants for most central collisions = 345 +- 10% PHENIX Collaboration October 2000 DNP meeting

  15. ET Analysis from Calorimetry PHENIX Preliminary Normalized to 10.7 barns • One-fourth of azimuthal coverage used for this analysis • Corresponds to 5184 5x5 cm2 towers • Minimum-bias trigger includes 7.2b strong, 3.7b mutual-Coulomb dissociation • Energy scale and e/p/p response checked at AGS & CERN, 1-70 GeV • Upper left shows correlation of ET with EZDC, expressed as # neutrons • Upper right is ds/dET for minimum-bias trigger • dET/dh, h=0, is 570 GeV +- 10% for 2% most central • See KC2 (Kistenev) PHENIX Collaboration October 2000 DNP meeting

  16. ET per Participant, per Charged Particle PHENIX PRELIMINARY PHENIX PRELIMINARY Number of Clusters in PC1 dET/dh per participant @ percentile NA49-WA98 @ SPS Au+Au 130A GeV Energy in EMCal (GeV) • dET/dh, h=0, is 570 GeV +- 10% for 2% most central • This is 40% higher than SPS result for 17.2 GeVA Pb+Pb • Energy density (Bjorken estimator) may be higher yet (i.e., more than 40% larger than at SPS) due to expectations that formation time, t0, is shorter at RHIC than SPS: many more soft gluons at RHIC • ET/participant (upper left) is 50% larger than for SPS • <ET>/<Ncharged particles> is about 1.05 GeV, a bit higher than SPS value PHENIX Collaboration October 2000 DNP meeting

  17. Conditions at Hadronic Freezeout • Current picture, from AGS and esp. claimed from SPS work, is that flavor and baryon content are to large extent locked in when hadrons are produced (“freezeout”) • Detailed study of hadrons emitted can shed light • pT spectra, invariant cross sections • Ratios • particle/antiparticle (p-/ p+, K-/K+, pbar/p) • strange/nonstrange (K/ p) • baryon/meson (p/ p) • Particularly interested in • strangeness and (net)baryon content mS, mB • mean pT, variation of invariant cross section with pT T • pT as function of particle species - evidence for collective motion? b • See JC6 (Ajitanand) • Cross section for short-lived particles, such as w and f vector mesons PHENIX Collaboration October 2000 DNP meeting

  18. Particle Identification using Time Of Flight • Time of Flight array • 1024 slats, PMT each end • Covers 1 EMCal sector • Presently <120ps resolution • Amplitude-slewing not corrected • Tracking system used for momentum reconstruction • Track association and momentum resolution still improving • Resulting spectrum shows • Both charge signs e/p/K/p • Separation to ~2 GeV/c • Good signal/background!! • See DC2 (Chujo), DC14 (Lebedev), JC10 (Mitchell) PHENIX Collaboration October 2000 DNP meeting

  19. Identified Charged-Hadron mT-m0 Spectra Raw distributions; acceptance and efficiency corrections yet to be applied ! See JC7 (Burward-Hoy/Velkovska), JC12 (Ghosh), DC13 (O’Brien), DC15 (Nandi) PHENIX Collaboration October 2000 DNP meeting

  20. Comparison of Charged and Neutral pT Spectra • pT spectra for charged particles taken from tracking spectrometer • pT spectra for p0 taken from EM calorimeter • Power-law fit is to UA1 data from CERN SppbarS • Encouraging agreement PHENIX Collaboration October 2000 DNP meeting

  21. p0 Identification and pT • Two photon invariant mass spectrum analyzed as function of pair pT • Observe expected peak at p0 mass • width all due to resolution • centroid and width stable with pT • magnitudes as expected from Monte Carlos study of detector response using PISA (PHENIX Integrated Simulation Algorithm) and HIJING event generator • Can see pairs in RHIC Au+Au !!! • Future pT reach thus governed by statistics, i.e. integrated luminosity PHENIX Collaboration October 2000 DNP meeting

  22. pT Spectra of p0 and EM Clusters • Inclusive EM clusters shown on left side (“almost photons”) • pT spectra of p0 on right for minimum-bias collisions • compared to WA98 p0 spectra for 10% most central collisions • WA98 is 17 GeVA Pb+Pb • PHENIX inverse slopes larger, already for minimum-bias events • PHENIX finds T=303 11 (stat)  67 (syst) MeV for p0 slope parameter • WA98 value is 180 MeV for low- pT, rising to 260 MeV for large pT • See DC10 (Mioduszewski), KC3 (Stankus) PHENIX Collaboration October 2000 DNP meeting

  23. Searching for Jet Quenching • Access timescales when matter is still deconfined • Propagation of partons affected by (deconfined?) medium • Wang & Gyulassy showed, for sufficiently large dE/dx, there are observable effects even for leading particles from jet fragmentation, i.e. in ‘singles’ • Attention to cross section normalization, energy scale essential for this study • “In progress” • Also affects angular correlation of high-pT particles • See DC4 (Ogilvie) PHENIX Collaboration October 2000 DNP meeting

  24. Year2001 Plans: Electrons via RICH • Vector meson decays to lepton pairs; radiation of virtual photons • Such signals should reflect medium modification/properties • Chiral symmetry restoration • Study f decays • Color-screening • Study J/y, y’ decays • Temperature, number density • Continuum lepton pairs • RICH for electron tagging • Field-off runs, look for converted g, results in 2 overlapped rings • Rings and tracks found aligned • Pulse height as expected from test beam data with RICH PHENIX Collaboration October 2000 DNP meeting

  25. Year2001: South Muon Arm Operation • Two muon arms being prepared • Nearly symmetric north/south • South one installs this winter • Statistics expected , 1 year run • 106 J/y, 104y’, 103U(1S) • Essential new addition to existing CERN data • U(1S) should never be “suppressed” at RHIC • J/y, y’ suppression vs. energy density, e, can be studied • For Au+Au, may be fully suppressed at RHIC! • Use Cu+Cu, Si+Si, p+A in succeeding years to map e dependence PHENIX Collaboration October 2000 DNP meeting

  26. Summary: PHENIX Year2000 • Spectrometers work! • Global behavior • ET /participant nucleon 50% higher than at SPS energies • Multiplicity, transverse energy per unit h increase ~40% vs. SPS • Scaling with # participants explored with Glauber model • <ET/<Ncp> slightly larger than at SPS • Spectra for identified particles • e/p/K/p all identified; p0 slope parameter larger than at SPS • pT spectra extend to above 4 GeV already for 1 ub-1 • Expect to reach pT = 20 GeV in Year 2001 for 2 nb -1 • Prospects for studying jet quenching at ‘inclusive’ level soon • Correlations to search for collective expansion and for effects due to in-medium modifications of parton propagation • Spectrometers, particle ID in place to commence vector meson program in Year2001 and do first “Spin” runs • Please see 28 more talks in parallel sessions !! PHENIX Collaboration October 2000 DNP meeting

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