Heavy Ion Collisions at Collider Energies Insights from

Heavy Ion Collisions at Collider Energies Insights from PHENIX ICPAQGC Axel Drees, SUNY Stony Brook Jaipur, India November 26, 2001 Results from run 2000 ~ 3. 5 106 minimum bias Au-Au events at s. NN = 130 Ge. V Global observables: ET and Nch Hadrons: yields and spectra suppression of high p. T hadrons Electron: inclusive spectra Other PHENIX talks: Tue. Session 6 Tue. Session 7 Fr. Session 19 David Silvermyr: Julia Velkovska: John Sullivan: Charged Particle Multiplicity in Au-Au Collisions at RHIC Identified Charged Hadron Production at RHIC Global Observables and Identified Hadrons in PHENIX

Pioneering High ENergy Ion EXperiment 11 Countries 51 Institutions 400+ Collaborators @ Axel Drees

PHENIX Physics Capabilities designed to measure rare probes: Au-Au & p-p spin + high rate capability & granularity + good mass resolution and particle ID - limited acceptance l 2 central arms: electrons, photons, hadrons l l l charmonium J/ , ’ -> e+evector meson r, w, -> e+ehigh p. T o, +, direct photons open charm hadron physics l 2 muon arms: muons l l l “onium” J/ , ’, -> m+mvector meson -> m+mopen charm l combined central and muon arms: charm production DD -> em @ l global detectors forward energy and multiplicity l event characterization Axel Drees

PHENIX Installation During Au-Au Run 2001 Mu. ID EMCAL TOF Mu. Trk TEC/TRD PCs DC RICH collaborator BBC MVD ZDC @ Axel Drees

PHENIX Setup During Year 2001 Run West Arm l tracking: DC, PC 1, PC 2, PC 3 electron ID: RICH, EMCal photons: EMCal l l East Arm tracking: DC, PC 1, TEC, PC 3 electron & hadron ID: RICH, TEC, TOF, EMC photons: EMCal l l Other Detectors l l South Arm l l tracking: Mu. Tr muon ID: Mu. ID @ Vertex & centrality: ZDC, BBC, MVD end of Au-Au run Nov. 26 ~200 106 Au-Au sampled 5 weeks of p-p run December/January full heavy ion program and first spin physics including electron & muon pairs Axel Drees

PHENIX Year 2000 Configuration Physics Results Presented in this Talk 12 detector systems in operation l h Neutral Pions l two photon mass EMCal (east & west) l Charged Particles l g g l tracking & momentum DC, PC 1, PC 3 + Inclusive Electrons l l electron ID: e. RICH, EMCal tracking & momentum DC and PC 1 p l Charged Hadrons l l Global Observables l l l @ event characterization ZDC, BBC transverse energy Pb. Sc charged particle multiplicity PC 1 & PC 2 l tracking & momentum DC, PC 1, PC 3 hadron ID TOF Axel Drees

Event Characterization central peripheral 5 -10% 5% correlation of zero degree energy (ZDC) with multiplicity of produced particles (BBC) l cover 92 4% of nuclear cross section in trigger l select event classes with certain fraction of cross section l Glauber model simulation of collision geometry and ZDC&BBC responds l @ Axel Drees

Transverse Energy and Energy Density Phys. Rev. Lett. 87, 52301 (2001) Bjorken estimate for initial energy density ET PHENIX me asu red formation time: 0. 2 - 1 fm central 2% e. Bj ~ 23. 0 Ge. V/fm 3 e. Bj ~ 4. 6 Ge. V/fm 3 Lattice ec Initial condition: energy density l significantly above expected critical density lattice: c ~ 0. 6 - 1. 2 Ge. V/fm 3 l > 1. 5 increase compared to CERN ( 0 ~ 1 fm) ~ 3. 2 Ge. V/fm 3 @ Axel Drees

Transverse Energy and Particle Production l ET increases faster than number of participants l ET/NPart larger than at CERN l ET / Nch ~ 0. 8 independent of centrality Phys. Rev. Lett. 87, 52301 (2001) ET / Nch (PHENIX excludes baryon mass, WA 98 includes baryon mass) @ charged particle production increases with centrality and s Axel Drees

Multi-Particle Production Charged particle density increases by: ~ 1. 3 from peripheral to central collisions ~ 1. 15 with s from 130 to 200 Ge. V Phys. Rev. Lett. 86, 3500 (2001) with quenching no jet quenching PHENIX Ansatz I: soft + hard component e. g. HIJING preliminary go see D. Silvermry tomorrow saturation hard component more pronounced in central collisions and at higher s Ansatz II: gluon saturation (all particle production from parton scattering) consistent with data: initial energy density ~ 18 Ge. V/fm 3 Eskola, Kajantie, and Tuominen: hep-ph/0009246 Kharzeev, Nandi: nucl-th/0012025 @ Axel Drees

PHENIX Hadron Identification l Charged hadrons via TOF effective resolution ~ 100 ps l Neutral mesons via EMCal two independent measurements: - Pb scintillator - Pb glass 2. 00 < pt < 2. 5 Ge. V 0 mgg @ Axel Drees

Hadron Yields as Function of Centrality l moderate 20% increase of pions l larger increase by factor ~1. 7 for kaons, protons and anti-protons significant fraction of d. N/d increase due to K, p and p increase 1. 2 1. 7 l large number of produced p and p l @ p/p ~ 0. 7 Axel Drees

Baryon Density at Mid Rapidity l substantial net baryon density at y = 0 (NB: <25% p from L decays included) l indication for increases with centrality more stopping in central collisions l 30% of net baryon density observed at CERN central collisions SPS Pb-Pb PHENIX Au-Au p – p participant nucleons (p– p ) A/Z 27 68 8. 6 1. 4 21. 4 d. N( p ) / dy produced baryons (p, p, n, n ) 5 ~ 20 20. 1 1. 0 80. 4 total baryon density ~90 ~100 PHENIX preliminary l large number of produced baryons and anti-baryons l sum of baryons + anti baryons increase slightly from SPS to RHIC @ Axel Drees

MT Spectra: Large Radial Flow l slope of transverse mass spectra increases with particle mass l pions and anti-protons well described by Hydro+Thermal model Hydro+Cascade D. Teaney et al. ~ 0. 6 c T~130 Me. V 5% central @ soft physics up to p. T ~ 3 Ge. V? Axel Drees

Transverse Momentum Spectra of Hadrons combine with 0 for maximum p. T coverage l excellent agreement between charged and neutral pions ! l pion and proton spectra from 0. 5 to 3. 5 Ge. V l (anti)proton yield increases above pion yield @ Axel Drees

Nucleon to Pion Ratios and Soft to Hard Transition empirical determination of soft/hard transition at ISR p/ rising with p. T up to 3 Ge. V p/ ratio m. T scaling p. QCD measured soft/hard transition p. T particle ratios have different p. T dependence for soft and hard component l ISR p-p soft/hard transition below 2 Ge. V l RHIC Au-Au soft/hard transition above 3 Ge. V? @ Axel Drees

Other PHENIX Preliminary Results on Hadron Production HBT charge and pt fluctuations Centrality: Gamma Distribution Calculation 0 -5% elliptic flow <Pt> (Ge. V/c) particle ratios and spectra see J. Velkovska’s talk on Tuesday and J. Sullivan’s talk on Friday for details @ Axel Drees

Hard Scattering in Heavy Ion Collisions large momentum transfer jets schematic view of jet production hadrons leading particle q power law spectrum pp = d 2 N/dpt 2 = A (p 0+pt)-n q hadrons leading particle N-N reference spectrum for Au-Au l interpolate pp data to 130 Ge. V l scale by number of binary collisions to Au-Au l pion reference scaled by 1/1. 6 ( /h ratio from ISR) @ Axel Drees

Suppression of High p. T Hadrons at RHIC l PHENIX first high pt data from RHIC l l l charged particle spectra at ~ 0 p. T range to ~ 5 Ge. V neutral pion spectra two independent data sets at ~ 0 out to 4 Ge. V central (0 -10%) and peripheral (60 -80%) Au+Au collisions Phys. Rev. Lett. (2001) in print PHENIX l comparison to N-N reference l peripheral collisions described at high p. T l central collision suppressed at high p. T @ Axel Drees

“Ordinary” Nuclear Effects Modifying pt Spectra l nuclear shadowing at small x at RHIC x ~ 2 p. T/ s < 0. 02 high p. T mostly in anti-shadowing region l initial state multiple scattering of partons: “Cronin effect” compiled by X. N. Wang modeled as pt broadening traditional analysis: saturates at ~ 2 above 2. 5 Ge. V increase above 1 at 1. 5 Ge. V @ “anomalous” nuclear enhancement > 1 above ~ 2 Ge. V/c Nuclear Modification Factor: Axel Drees

Nuclear Modification Factor Au-Au to p-p Phys. Rev. Lett. (2001) in print PHENIX l ratio exhibits characteristic features: l charged: increases up to ~ 2 Ge. V saturates at RAA ~ 0. 6 l neutral pions: ~ constant at RAA ~ 0. 4 l difference between 0 and h l large proton contribution at RHIC l estimate of systematic error l data: charged 16 - 30 % 0 21 - 35 % l <N binary> 11 % l NN ref. 20 - 35 % total 30 - 50 % (p. T dependent) within systematic errors: RAA < 1 @ Axel Drees

Centrality Dependence of the Charged Hadron Suppression F. Messer, PHENIX, QM 2001, updated PHENIX preliminary l centrality dependence of charged particle production l full systematic available for 92% of interaction cross section l gradual change from central to peripheral l calculate RAA for 5 centrality bins (normalize to Nbinary and divide by N-N reference) @ Axel Drees

Centrality Dependence of the Nuclear Modification Factor l peripheral sample: “Cronin effect”? l continuos increase l increases above unity but, at high pt l central sample: “high pt suppression” l continuous modification of spectra pt > 2. 0 Ge. V decrease of slope with centrality PHENIX preliminary pt < 1. 5 Ge. V increase of slope with centrality increasing Kaon contribution? peripheral central /Nbinary expect opposite effect from p&p!! pt overall decrease of yield relative to Nbinary* pp systematic error large @ Axel Drees

Increasing Suppression of Charged Hadrons with Increasing p. T yield integrated above p. T cut average p. T above p. T cut PHENIX preliminary l yield/Nbinary l decreases for 1. 8 Ge. V cut l decreases faster for higher p. T l yield/Npart l increases for 1. 8 Ge. V cut l similar to Nch l scales with Npart for 3. 5 Ge. V cut @ l p. T - p. Tmin l l l decreases by ~50 Me. V for 1. 8 Ge. V cut not due to proton contribution slope mesonic spectra decrease faster gradual onset of suppression with centrality and p. T Axel Drees

Inclusive Electron Production l contributions to electron spectra l photon conversions l Dalitz decays l vector meson decays excess above these contributions l open charm decays l tune Pythia to all existing data l extrapolate cc ~ 350 mb at 130 Ge. V l scale to central Au-Au with Nbinary large charm contribution above 1. 0 Ge. V consistent with data @ Axel Drees

Large Amounts of Results from PHENIX l global observables l Initial energy density > 4. 6 Ge. V/fm 3 l d. Nch/d and d. ET/d hard+soft component or gluon saturation l hadron p. T spectra: soft physics l d. Nbaryon/dy ~ 100 (baryon + anti-baryon) l hydro+thermal interpretation of p. T spectra large radial flow l hadron p. T spectra: hard physics l p/ increases up to 3. 5 Ge. V to values above 1 no sign of soft/hard transition l high p. T charged hadron and 0 yield suppressed in central collisions different from Cronin effect and shadowing l continuous centrality dependence: peripheral similar to Cronin effect l suppression sets in gradually for more central collisions l increasing centrality: decreasing relative yield with increasing p. T l increasing centrality: decreasing average p. T above 1. 8 Ge. V l electron spectra l consistent with large charm cross section 3. 5 106 event in 2000 ~200 106 events in 2001 + pp data @ Axel Drees

Mean Transverse Momentum vs Centrality 20+/- 5 % increase l Mean p. T growing with Npart and mass - consistent with flow l (Anti) proton p. T significant increase from pp collisions l The same relative increase from peripheral to central for all particles @ Axel Drees