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2 Outline:  Motivation.  QGP Search at RHIC  Charm scenario  PHENIX experiment at RHIC  Open charm  Methods  Results  J/Ψ Measurements  Methods  Results  Outlook

3 critical temperature T C Results from lattice QCD establish the QCD phase transition  nuclear matter p, n Quark-Gluon Plasma q, g density or temperature What is QGP phase transition:  What we expect:  Critical energy ε C ~ 6  2 T C 4  T C ~ MeV  ε C ~ GeV/fm 3

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5 e  space time Hard Scattering Au  Expansion  Hadronization  Freeze-out jet J/  QGP Thermaliztion  e p K   

6 0-10% Central 200 GeV AuAu Search for QGP at RHIC  Global observables:  Particle yields and ratios  HBT  Flow  Spectra  Penetrating probes:  High pT suppression  Jet “disappearance”  Heavy quarks  Direct radiation  Light mesons time M T (GeV/c 2 ) e+e-e+e- 1/2  m T dN/dm T dy (GeV/c 2 ) -2 K+K-K+K- PHENIX Preliminary

7  Charm yield in heavy-ion collisions  production mainly via gluon-gluon fusion in the earliest stage of the collision.  additional thermal production at very high temperature  enhancement?  Propagation through dense medium  energy loss by gluon radiation?  softening of “charmed hadron” spectra?  Does charm flow? sensitive to initial gluon densitysensitive to initial temperaturesensitive to state of nuclear mediumsensitive to collectivity on partonic level Motivation: Open charm production

8  cc: produced early / embedded in medium  can form bound state: J/   deconfinement & color screening  J/  suppression (Matsui and Satz, PLB176(1986)416)  Central Pb+Pb collisions at SPS  J/y suppression in excess of “normal” nuclear suppression (NA50: PLB477(2000)28)  Prospects at RHIC  higher cc yield than at SPS  possible J/Ψ enhancement due to cc coalescence as the medium cools  important to measure J/Ψ in pp and dAu to separate “normal” nuclear effects (anti) shadowing nuclear absorption in cold matter  open charm needed as baseline Motivation: Charmonia (J/Ψ)

9 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 Florida Technical University, Melbourne, FL Georgia State University, Atlanta, GA University of Illinois Urbana Champaign, 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 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 Rikkyo University, Tokyo, Japan 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; 58 Institutions; 480 Participants* *as of January 2004

10 The only RHIC experiment optimized for lepton measurements two forward muon spectrometers two central electron/photon/hadron spectrometers  electrons: central arms  electron measurement in range: |η|  0.35 p  0.2 GeV/c  muons: forward arms  muon measurement in range: 1.2 < |η| < 2.4 p  2 GeV/c PHENIX experiment at RHIC

11 PHENIX experiment at RHIC  Central arms:  Tracking by DC and PC by measuring track angle after magnetic field  e-ID by RHIC using Cherenkov light  e-ID by EMCal by E/p matching and shower profile  Muon arms:  Tracking by μ-trackers in the magnetic field (azimuthal)  μ-ID by particle penetration depth in muon identifiers stations  Trigger and centrality  Beam-beam counters at 3<|η|<4 (amplitude and timing)  ZDC non-participation neutron energy

12  Ideal but very challenging: direct reconstruction of charm decays (e.g. ) D0  K- +D0  K- +  Alternative but indirect: charm semi leptonic decays contribute to single lepton and lepton pair spectra: D 0 +D 0 0 < p T < 3 GeV/c, |y| < 1.0 d+Au minbias Open charm measurement

13  Example of “Cocktail method”:  Reconstruct inclusive e ± spectra from Au+Au at 130 GeV.  Use available data to establish “cocktail” of e ± sources. dominated by measured π 0 decays and photon conversions. “photonic sources” are photon conversions and Dalitz decays  Excess above cocktail  increasing with p T  expected from charm decays  Subtract cocktail from data  Attribute excess to semileptonic decays of open charm  First “measurement” of open charm in HI collisions PHENIX: PRL 88(2002)  conversion  0   ee    ee, 3  0   ee,  0 ee   ee,  ee   ee  ’   ee Open charm via single electrons

14  Converter method:  add converter of known thickness to experiment  compare e ± spectra with and without converter  separation of e ± from photonic and non-photonic sources  e-γ coincidence method:  e ± from photonic sources are correlated with a γ  separation of e ± from different sources  Three independent methods to measure electrons from non- photonic sources! Open charm via single electrons

15 PHENIX PRELIMINARY  non-photonic e ± from p+p collisions at 200 GeV  PYTHIA tuned to lower energy data (√s < 63 GeV)  for p T > 1.5 GeV/c spectra are “harder” than PYTHIA prediction PHENIX PRELIMINARY  spectral shape  PYTHIA charm & bottom line shapes with normalizations as independent free parameters  total cross section  PYTHIA describes data at low p T  use PYTHIA to extrapolate to full phase space Open charm in pp collisions at 200 GeV Reference for HI

16 PHENIX PRELIMINARY  non-photonic e ± from d+Au collisions at 200 GeV  cross section divided by the nuclear overlap integral T AB to account for the difference in system size between p+p and d+Au  very good agreement of d+Au data with the scaled p+p reference within uncertainties  no indication for strong cold-nuclear matter modifications  how about centrality dependence? 1/T AB EdN/dp 3 [mb GeV -2 ] Open charm in dAu at 200 GeV

17  Use Glauber MC + Negative Binominal Distribution + Uncorrelated hit assumption Centrality in dAu (example)  Get Ncoll / Npart for Min Bias and for any given centrality bin

18 PHENIX PRELIMINARY 1/T AB 1/T AB EdN/dp 3 [mb GeV -2 ] Centrality (in)dependence in dAu

19 1/T AB EdN/dp 3 [mb GeV -2 ] PHENIX  Non-photonic e ± from Au+Au collisions at 200 GeV  cross section divided by the nuclear overlap integral TAB to account for the difference in system size between p+p and Au+Au  very good agreement of Au+Au data with the scaled p+p reference within uncertainties up to p T = 1.5 GeV/c  at higher p T more statistics is needed  no indication for strong medium modifications  how about centrality dependence? Open charm in AuAu at 200 GeV

20 1/T AA 1/T AB EdN/dp 3 [mb GeV -2 ] More statistics is highly desirable! Available in Run4 Centrality (in)dependence in AuAu

<  <  charm production seems to scale with T AB, i.e. with the number of binary collisions N Coll  determine dN/dy of electrons in the measured range of p T and test its consistency with dN/dy = A (N coll )   the 90 % Confidence Level on a is shown as yellow band Binary scaling in AuAu

22 PHENIX PRELIMINARY  charm flow could indicate partonic flow, i.e. collectivity on the parton level  v 2 measures the 2 nd harmonic of the Fourier expansion of the azimuthal distribution of particle emission with respect to the reaction plane  v 2 of e ± from non-photonic sources is related to charm v 2 !  uncertainties are too large to make a definite statement! Does Charm flow?

23  PHENIX: inclusive electrons in p+p, d+Au, and Au+Au at √s NN = 200 GeV  yield of electrons from non-photonic sources  consistent with binary scaling  no indication for strong enhancement / suppression of charm cross section in nuclear collisions  statistics limited regarding:  presence of spectral modifications in Au+Au (energy loss)?  charm flow in Au+Au?  to be answered by Run-4 data (just finished)  charm data as baseline for J/Ψ measurements! Summary: Open charm at RHIC

24 J/  →e + e - J/Ψ→μ + μ - (north μ-arm)  subtraction of combinatorial background by subtraction of like-sign dilepton mass spectra from unlike-sign spectra  (small) physical background remains +-+- ±±±± J/Ψ in dAu at 200 GeV

25  preparing the case (need integrated luminosity!)  study modification of J/  production in cold nuclear matter: p+p versus d+Au! YearIons  s NN Detectors J/  2000Au-Au130 GeV Central (electrons) Au-Au200 GeV Central [1] 2002 p-p200 GeV + 1 muon arm [2] 2002 d-Au200 GeV Central p-p200 GeV + 2 muon arms Au-Au200 GeVdata exists~400+2x1600 ? first J/Ψ observation at RHIC first sizeable samples in p+p & d+Au J/Ψ: suppression vs enhancement?

26 X1X1 X2X2 J/  in North y > 0 X1X1 X2X2 J/  in South y < 0 rapidity y Example of predicted “gluon shadowing” in dAu gluons in Pb / gluons in p X Anti Shadowing J/Ψ   +  - analysis for d+Au & p+p North μ-armSouth μ-arm d Au Central Arm From Eskola, Kolhinen, Vogt: Nucl. Phys. A696 (2001)  three rapidity ranges probe different momentum fractions x 2 of Au partons –South (y < -1.2) : large X 2 (Au) ~ –Central (y ~ 0) : interm. X 2 ~ –North (y > 1.2) : small X 2 (Au) ~  (anti)shadowing ↔ (enhancement) depletion of (high) low momentum partons

27 High x 2 ~ 0.09 Low x 2 ~ J /  ratio (d+Au / p+p) versus p T increase of  with increasing p T → p T broadening of J/  (initial state multiple scattering, Cronin effect) similar to measurements at lower energy (E866: √s = 39 GeV)

28 BR  pp = 160 nb ± 8.5 % (fit) ± 12.3% (abs) - preliminary J/  J /  cross section versus rapidity

29 Klein,Vogt, PRL 91:142301,2003 Kopeliovich, NP A696:669,2001  compared to lower  s Low x 2 ~ (shadowing region) R dA 1 st J/ψ’s at large negative rapidity! J /  ratio (d+Au / p+p) versus rapidity  data indicate nuclear effects (difficult to disentangle)!  weak shadowing  weak absorption

30 High x 2 ~ 0.09 Low x 2 ~ R cp  define four centrality classes for d+Au collisions  determine N coll for each class in a Glauber model  calculate R cp  low and medium x 2  weak nuclear effects  small (shadowing) centrality dep.  high x 2  steep rise with centrality  how can antishadowing rise so steeply while shadowing does not?  final state effect in Au remnants (close to Au frame)? Central / Peripheral in dAu 200 GeV

31  cold nuclear matter effects have been observed in d+Au collisions  weak gluon shadowing  weak absorption  p T broadening: similar to lower energy data  disentangling these effects requires more data  modest baseline for J/  measurements in Au+Au collisions is available: the stage is set!  Run-4 (Au+Au at 200 GeV) run is finished, analysis is currently ongoing! –smaller than expected from lower energy data Summary: J/Ψ at RHIC

32  J/  production in Au+Au at 200 GeV (Run-4)  a first J/  signal in the dielectron channel  stay tuned! J/Ψ in AuAu outlook