html5-img
1 / 85

The PHENIX White Paper

The PHENIX White Paper. STAR collaboration meeting. Barbara V. Jacak Stony Brook July 12, 2004. outline. Introduction to PHENIX & our physics approach Energy density Thermalization & Collectivity High p T phenomena jet quenching and binary scaling of high p T g , charm s Hadronization

yagil
Download Presentation

The PHENIX White Paper

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The PHENIX White Paper STAR collaboration meeting Barbara V. Jacak Stony Brook July 12, 2004

  2. outline • Introduction to PHENIX & our physics approach • Energy density • Thermalization & Collectivity • High pT phenomena • jet quenching and binary scaling of high pTg, charm s • Hadronization • Baryons, jet fragmentation and recombination • Where to go from here?

  3. vacuum QGP did something new happen at RHIC? • Study collision dynamics (via final state) • Probe the early (hot) phase Equilibrium? hadron spectra, yields Collective behavior i.e. pressure and expansion? elliptic, radial flow Particles created early, predictable quantity, interact differently in QGP vs. hadron matter fast quarks/gluons, J/Y, D mesons thermal radiation

  4. Brazil University of São Paulo, São Paulo China Academia Sinica, Taipei, Taiwan China Institute of Atomic Energy, Beijing Peking University, Beijing France LPC, University de Clermont-Ferrand, Clermont-Ferrand Dapnia, CEA Saclay, Gif-sur-Yvette IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, Orsay LLR, Ecòle Polytechnique, CNRS-IN2P3, Palaiseau SUBATECH, Ecòle des Mines at Nantes, Nantes Germany University of Münster, Münster Hungary Central Research Institute for Physics (KFKI), Budapest Debrecen University, Debrecen Eötvös Loránd University (ELTE), Budapest India Banaras Hindu University, Banaras Bhabha Atomic Research Centre, Bombay Israel Weizmann Institute, Rehovot Japan Center for Nuclear Study, University of Tokyo, Tokyo Hiroshima University, Higashi-Hiroshima KEK, Institute for High Energy Physics, Tsukuba Kyoto University, Kyoto Nagasaki Institute of Applied Science, Nagasaki RIKEN, Institute for Physical and Chemical Research, Wako RIKEN-BNL Research Center, Upton, NY University of Tokyo, Bunkyo-ku, Tokyo Tokyo Institute of Technology, Tokyo University of Tsukuba, Tsukuba Waseda University, Tokyo S. Korea Cyclotron Application Laboratory, KAERI, Seoul Kangnung National University, Kangnung Korea University, Seoul Myong Ji University, Yongin City System Electronics Laboratory, Seoul Nat. University, Seoul Yonsei University, Seoul Russia Institute of High Energy Physics, Protovino Joint Institute for Nuclear Research, Dubna Kurchatov Institute, Moscow PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg St. Petersburg State Technical University, St. Petersburg Sweden Lund University, Lund 12 Countries; 57 Institutions; 460 Participants USA Abilene Christian University, Abilene, TX Brookhaven National Laboratory, Upton, NY University of California - Riverside, Riverside, CA University of Colorado, Boulder, CO Columbia University, Nevis Laboratories, Irvington, NY Florida State University, Tallahassee, FL Georgia State University, Atlanta, GA University of Illinois Urbana Champaign, IL Iowa State University and Ames Laboratory, Ames, IA Los Alamos National Laboratory, Los Alamos, NM Lawrence Livermore National Laboratory, Livermore, CA University of New Mexico, Albuquerque, NM New Mexico State University, Las Cruces, NM Dept. of Chemistry, Stony Brook Univ., Stony Brook, NY Dept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY Oak Ridge National Laboratory, Oak Ridge, TN University of Tennessee, Knoxville, TN Vanderbilt University, Nashville, TN

  5. PHENIX at RHIC 2 Central spectrometers 2 Forward spectrometers 3 Global detectors

  6. methods • Tracking: drift chamber + pad chambers outside field • Hadron PID: High res. TOF (s ~ 80 ps) sector • identify higher pT pions via p0gg, RICH for charged • Photons: high granularity and resolution EMCAL • Leptons • Electrons in central arm: tracking + RICH, EMCAL • Muons forward/backward: magnet pole face absorbs hadrons, 3 tracking stations inside muon magnet + additional absorber with sampling inside • Centrality: ZDC + BBC to avoid autocorrelations • Reaction Plane: BBC to avoid autocorrelations

  7. PHENIX looks for J/Y  e+e- and m+m- Need e/p separation 1/10,000 All tracks: 0.8>p>0.9 GeV/c enriched sample (w/ RICH cut) E/p Ring Imaging Cherenkov counter to tag electrons “RICH detector” For e: vpart. > cmedium

  8. Philosophy • Optimize for rare probes • Particle ID to high pT • High resolution for high pT performance • tradeoff: above is expensive, pay for by losing acceptance • Triggering and DAQ capability • Trigger various channels besides min bias • high pT photons: calorimeter showers • muons: MuID hits; select singles or muon pairs • electrons: RICH hits + overlapping energy in EMCAL • select thresholds for sufficient rejection in AuAu, pp, etc. • DAQ: 100 MB/sec gives bandwidth for ALL AuAu until • second half of run 4 (limited acceptance = smaller events)

  9. Colliding system expands: Energy  to beam direction per unit velocity || to beam pR2 2ct0 What energy density is achieved? PRL87, 052301 (2001) • e 5.5 GeV/fm3 (200 GeV Au+Au) Using t0 = 1 fm/c well above predicted transition!

  10. Initial Energy density • dET/dy(t0) > dET/dyfinal = 1.25 x dET/dhfinal = 760 GeV • Three values of t0 • tmin = 2R/g = 0.13 fm/c (RHIC) = 1.6 fm/c (SPS) • = 5.3 fm/c (AGS) • tform=ħ/<mT (tform) > • ≤ħ/<mT>final = 0.35 fm/c • <mT>=(dET/dh)/(dN/dh)=0.57 GeV) • ttherm≤ 1 fm/c (hydro-models) • ≤ 2 fm/c (upper limit) • Conservative lower limits on e • at formation and thermalization • e(form) > 15 GeV/fm3 (t = 0.35 fm/c) • e(therm) > 2.8 GeV/fm3 (t = 2.0 fm/c) • These values >> ~1 GeV/fm3 from • lattice QCD • Question: what could it be if not QGP??

  11. Thermalization? particle ratios and spectra Statistical fit:Tch~ 160MeV, gs~1.0 Strangeness saturation at RHIC? p/K/p measurement in a Broad pt range • consistent with strongly expanding thermalized source • observed strangeness production  complete chemical equilibrium Chemical freezeout Thermal freezeout stronger radial flow at RHIC? RHIC Expansion velocity Tkin ~ 100 MeV <bT> ~ 0.5

  12. rapid thermalization? elliptic Flow v2/ecc vs centrality v2 of p/K/p and hydro • v2 scaling with eccentricity  collectivity built up at early stage • hydro-models with hadronic + QGP phases reproduce (qualitatively) measured v2(pT) of pions, kaons, and protons.

  13. proton pion Is thermalization achieved?v2 & spectra vs. hydrodynamic models Hydro models: Teaney (w/ & w/o RQMD) Hirano (3d) Kolb Huovinen (w/& w/o QGP)

  14. HBT vs. hydro models NB: Rside  source transverse radius! Nobody gets HBT right! Origin of the “HBT puzzle” Generic explanation: Nobody does freezeout of final state right Another explanation: Maybe we’re fooled by the extraction of the radius parameters somehow

  15. Thermalization? Hydro-models score board • hadronic + QGP hydro reproduces features of v2(pT) of p, K, p • require early thermalization (ttherm<1fm/c) + high einit > 10 GeV/fm3 • most fail to get v2 and spectra simultaneously • unequivocal statement on presence of QGP not yet possible • HBT source parameters not reproduced by hydro • inconsistencies prevent firm conclusions (boo) Source average

  16. Collision energy dependence (dNch/dh)/(0.5Npart) vs s1/2 Elliptic flow dv2/dpT vs s1/2 • Large dET/dh, dNch/dh, strangeness enhancement, strong radial flow, and elliptic flow have been observed in heavy ion collision at lower energy. • smooth changes as a function of s1/2 from AGS to SPS to RHIC energies. • No sudden change with collision energy has been observed.

  17. 0.906 <  < 1.042 dN/dy = A (Ncoll) Ncoll Scaling of point-like probes Charm yield scales with Ncoll Direct photon scales with Ncoll • charm yield and direct photons experimental verification of binary scaling of point-like pQCD processes. Direct g from Au+Au @200GeV Electron from charm decay in Au+Au @200 GeV

  18. Direct Evidence of High (parton) Density MatterHigh pT suppression • The strong suppression of high pT production is a unique phenomenon that has not been previously observed. • Deuteron-Gold measurements demonstrate that any initial-state modification of parton distributions causes little or no suppression. • Direct evidence that Au+Au collisions at RHIC have produced matter at extreme density

  19. Cronin effect from pions in 3 detectors • Charged pions from TOF • Neutral pions from EMCAL • Charged pions from RICH+EMCAL Cronin effect gone at pT ~ 8 GeV/c

  20. Au-Au s = 200 GeV: high pT suppressed! PRL91, 072301(2003)

  21. Evidence of jet origin of high pT particles High pT two particle correlation xT scaling of p0 and charged • xT = 2pT /s related to pT of scattered parton; F is xT dependent • scaling in Au+Au  dominant role of hard scattering and subsequent jet fragmentation in the production of high pT hadrons. p0 (h+ + h-)/2 scales

  22. Parton energy loss RAA data vs GLV model • GLV: initial gluon density dng/dy~1000 & einit~15 GeV/fm3 • consistent with einit from our dET/dh, hydro models Medium induced energy loss: only currently known physical mechanism to consistently explain the high pT suppression.

  23. Empirical energy loss from data For power-law spectrum with A/pTn (we find n= 8.1 in pp) Final spectrum = initial - <fractional shift> <shift> due to eloss of parent parton Parent pT would be: pT’ = (1+S) pT(pp) Fractional energy loss: Sloss = 1 - 1/(1+S) 10 GeV: DE/Dx ~ 0.5 GeV/fm Fractional energy loss

  24. Anomalous p/p ratio Proton scales with Ncoll Mesons don’t Large p/p ratio in 2-4 GeV/c • (anti)baryon to pion excess: most striking experimental surprise at RHIC • new mechanism other than universal parton fragmentation is the dominant source of baryons in the intermediate pT range.

  25. Is Recombination the answer? Recomb. Models explain large p/p • Recombination models: natural explanation for baryon/meson • & apparent quark number scaling of v2 They also predict v2/n scaling

  26. But baryons show jet-like properties too… Baryons at 2-4 GeV/c pT scale with Ncoll !

  27. Jets in PHENIX • Large multiplicity of charged particles • --solution: find jets in a statistical manner • using angular correlations of particles • mixed events give combinatorial background • 2 x 90 degree acceptance in phi and ||<0.35 --solution: correct for azimuthal acceptance, but not for  acceptance • Elliptic flow correlations • --solutions: • use published strength values • and subtract • (or integrate over 90° then • all even harmonics are zero) PHENIX PRL 91 (2003) 182301

  28. CARTOON flow+jet flow N F Jet physics in PHENIX trigger Trigger: hadron with pT > 2.5 GeV/c Count associated particles for each trigger at lower pT (> 1 GeV/c) • “conditional yield” Near side yield: number of jet associated particles from same jet in specified pT bin Away side yield: jet fragments from opposing jet Intra-jet pairs angular width : N |jTy| Inter-jet pairs angular width : F |jTy|  |kTy| “near side”  < 90° jet partner “away side”  > 90° opposing jet

  29. PHENIX 2 particle correlations Select particles with pT= 2.5-4.0GeV/c Identify them as mesons or baryons via Time-of-flight Find second particle with pT = 1.7-2.5GeV/c Plot distribution of the pair opening angles

  30. Underlying event is big! Collective flow causes another correlation in them: associated particles with non-flow angular correlations -> jets! Treat as 2 Gaussians B(1+2v2(pTtrig)v2(pTassoc)cos(2)) Subtract the underlying event includes ALL triggers (even those with no associated particles in the event) combinatorial background in Au+Au Measure by mixed events & subtract CARTOON 1 dN flow+jet Ntrig d flow jet

  31. Is recombination the answer? Jet correlation with leading proton, meson pT trig:2.5-4 GeV/c Count partners 1.7–2.5 GeV/c • correlations of particles with leading baryons rule out the simplest recombination models, which assume a perfectly thermal source of partons. • At present, no complete understanding of hadron formation

  32. Answer to Q0 • Q0: Does central Au+Au collisions produce a state of matter? • Answer: Yes. Evidence 1: Jet suppression in Au+Au collision • Suppression of high pT particles in Au+Au • Jet origin of high pT particles demonstrated by two particle correlation and xT scaling • Absence of suppression in d+Au • TAB scaling of direct photon and charm yield in Au+Au These observations provide a direct evidence that a dense matter formed in the final state is the cause of the suppression. Evidence 2: Strong elliptic flow • Scaling of v2 with eccentricity shows that a high degree of collectivity built up at a very early stage of collision • Success of hydrodynamic models in reproducing the elliptic flow shows that the state can be well described as fluid – a matter.

  33. Answer to Q1 • Q1: If the answer is yes, is it conceivable that the state of matter consisted only of hadrons? • Answer: No • The lower limit of the energy densities derived from dET/dh are: • e≥ 15 GeV/fm3 at formation at t≤ 0.35 fm/c • e≥ 2.8 GeV/fm3 at thermalisation at t ≤ 2 fm/c • The hydro-models require early thermalization (ttherm<1fm/c) and high initial energy density e > 10 GeV/fm3 • Initial gluon density dng/dy~1000 and initial energy density e~15 GeV/fm3 are obtained from GLV model of jet quenching. A similarly high initial energy density is obtained by other models. All these estimates of energy density are well in excess of ~1 GeV/fm3 obtained in lattice QCD as the energy density needed to form a deconfined phase.

  34. Answer to Q2 • Q2: If the answer is no, is the state of matter QGP? • Answer: We don’t know. • + We know that the matter is extremely dense and it thermalize very rapidly. The estimated energy densities are all well in excess of the density needed for a QGP. • But • There is no directevidence that • the matter is deconfined • the primary degree of freedom of the matter is quark and gluons • the matter is at high temperature (T > 170 MeV) • We currently do not have a consistent model of Au+Au collision that can describe spectra, v2, and HBT. This prevents us from drawing quantitative conclusions on the properties of the matter such as the equation of state and the presence of a mixed phase. • furthermore • There is no obvious and common definition of QGP.

  35. Answer to Q3 • Q3: What key questions remains to be answered? • Answer: • The term “QGP” should be better defined • Key predictions that derive from the properties of above defined QGP should be given, and these predictions should be tested by RUN4 data. For example: • RAA at very high pT (Test of jet quenching models) • g + jet coincidence (Test of jet quenching models) • Fate of J/y (Test of deconfinement/recombination) • Charm energy loss (Test of energy loss models) • Thermal radiation (Measurement of the temperature) • A consistent model of heavy ion reactions should be constructed so that we can relate the experimental observables to the property of matter in a quantitative and consistent way. • The theory community should work towards • Increased cross comparison of both definitions and model results • More rigorous bounds on values of extracted parameters (e, EOS, etc)

  36. p-p hep-ex/0304038 Good agreement with NLO pQCD Parton distribution functions Fragmentation functions s = 200 GeV, hard probesstart with pQCD & pp collisions Works! A handle on initial NN interactions by scattering of q, g inside N We also need: p0

  37. min bias 200 GeV Au+ Au PHENIX measures v2 two ways: • 2 particle correlations • Gets tricky at high pT, jets can contribute • Determine reaction plane at y = 3-4 • From BBC, with full azimuthal symmetry • Measure hadrons in central arms, sort vs. reaction plane • No jet effects upon found reaction plane

  38. Implication #1 of fast equilibration & large v2 Huge cross sections!!

  39. p above p for • pT < 2 GeV/c. • Then crosses over • Values ~ saturate • at high pT • geometry? • v2/quark seems • almost constant •  create hadrons • by coalescence of • quarks from • boosted distribution? Implication #2 (from flavor dependence) nucl-ex/0305013

  40. Au-Au s = 200 GeV: high pT suppression! PRL91, 072301(2003)

  41. Suppression: a final state effect? Hadron gas • Hadronic absorption of fragments: • Gallmeister, et al. PRC67,044905(2003) • Fragments formed inside hadronic medium • Energy loss of partons in dense matter • Gyulassy, Wang, Vitev, Baier, Wiedemann… Absent in d+Au collisions! d+Au is the “control” experiment

  42. probe rest frame r/ ggg Suppression: an initial state effect? • Gluon Saturation • (color glass condensate) Wavefunction of low x gluons overlap; the self-coupling gluons fuse, saturating the density of gluons in the initial state.(gets Nch right!) • Initial state elastic scattering (Cronin effect) Wang, Kopeliovich, Levai, Accardi • Nuclear shadowing Levin, Ryshkin, Mueller, Qiu, Kharzeev, McLerran, Venugopalan, Balitsky, Kovchegov, Kovner, Iancu … RdAu~ 0.5 D.Kharzeev et al., hep-ph/0210033 Broaden pT :

  43. Compare centrality dependence to control Au + Au Experiment d + Au Control • Dramatically different and opposite centrality evolution of AuAu experiment from dAu control. • Jet suppression is clearly a final state effect.

  44. Centrality dependence of Cronin effect • Probe response of coldnuclear matter with increased number of collisions. • See larger Cronin effect for baryons than for mesons (as at Fermilab) Qualitative agreement with model by Accardi and Gyulassy. Partonic Glauber-Eikonal approach: sequential multiple partonic collisions. nucl-th/0308029

  45. Does Cronin enhancement saturate? • A different approach: • Intrinsic momentum broadening in the excited projectile proton: • hpA: average number of collisions: X.N.Wang, Phys.Rev.C 61 (2000): no upper limit. Zhang, Fai, Papp, Barnafoldi & Levai, Phys.Rev.C 65 (2002): n=4 due to proton d dissociation.

  46. Questions we can ask • What is the intrinsic (primordial) parton transverse momentum kT? • In a nucleon? Nucleus? • Defines baseline for modifications • What is the fragmentation function? • Shape & width, defined by jT, in p+p collisions • Flavor composition of fragments, to compare observed baryon/meson yields in Au+Au • vital for understanding of mechanism of parton interaction with QCD medium formed at RHIC

  47. jet fragmentation and  momentum |ky| = mean effective transverse momentum of the two colliding partons in the plane  to beam axis |jy| = mean transverse momentum of the hadron with respect to the jet axis (in the plane  to beam axis)

  48. pp and dAu correlation functions 1<pT<1.5 2.2<pT<6.0 p+p h+- correl. Near angle peak Far angle peak d+Au : 5<pT <16 GeV/c assoc. with h+- Fit = const + Gauss(0)+Gauss()

  49. from jet correlations in pp at s = 200GeV PHENIX preliminary |jTy| = 36715 MeV/c z  |kTy| = 66050 MeV/c |kTy| = 920100 MeV/c PHENIX preliminary

  50. Jet cone “width” independent of s * *Subject to same trigger bias by selecting pT of particles CCOR Collaboration Phys. Lett. 97B(1980)163

More Related