Ralf Averbeck State University of New York at Stony Brook for the Collaboration DPG Spring Meeting Cologne, Germany, March 8-12, 2004 Heavy-flavor measurements with the PHENIX experiment at RHIC

R. Averbeck, 2 DPG Meeting, Cologne, 3/8/2004 Outline l Motivation l RHIC l Open heavy-flavor (charm) measurements l method l selected results l Heavy quarkonia (J/  ) measurements l method l selected results l Summary l Outlook

R. Averbeck, 3 DPG Meeting, Cologne, 3/8/2004 l charm yield in heavy-ion collisions l production mainly via gluon-gluon fusion in the earliest stage of the collision l additional thermal production at very high temperature  enhancement? l propagation through dense medium l energy loss by gluon radiation?  softening of “charmed hadron” spectra? l does charm flow? Motivation I: open charm production sensitive to initial gluon densitysensitive to initial temperaturesensitive to state of nuclear mediumsensitive to collectivity on partonic level

R. Averbeck, 4 DPG Meeting, Cologne, 3/8/2004 l cc: produced early / embedded in medium can form bound state: J/  deconfinement & color screening  J/  suppression (Matsui and Satz, PLB176(1986)416) Motivation II: charmonia (J/  ) l central Pb+Pb collisions at SPS J /  suppression in excess of “normal” nuclear suppression (NA50: PLB477(2000)28) l prospects at RHIC l higher cc yield than at SPS possible J /  enhancement due to cc coalescence as the medium cools important to measure J /  in p+p and d+A to separate “normal” nuclear effects l (anti) shadowing l nuclear absorption in cold matter l open charm needed as baseline

R. Averbeck, 5 DPG Meeting, Cologne, 3/8/2004 RHIC l only RHIC experiment optimized for lepton measurements two forward muon spectrometers two central electron/photon/hadron spectrometers l electrons: central arms electron measurement in range:  0.35 p  0.2 GeV/c l muons: forward arms muon measurement in range: 1.2 < |  | < 2.4 p  2 GeV/c

R. Averbeck, 6 DPG Meeting, Cologne, 3/8/2004 l ideal but very challenging direct reconstruction of charm decays (e.g. ) How to measure open charm D0  K- +D0  K- + l alternative but indirect l 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

R. Averbeck, 7 DPG Meeting, Cologne, 3/8/2004 l cocktail method (example) l inclusive e ± spectra from Au+Au at 130 GeV l use available data to establish “cocktail” of e ± sources –dominated by measured  0 decays and photon conversions –“photonic sources” are photon conversions and Dalitz decays l excess above cocktail l increasing with p T l expected from charm decays l subtract cocktail from data l attribute excess to semileptonic decays of open charm l first “measurement” of open charm in HI collisions Open charm via single electrons (I) PHENIX: PRL 88(2002)  conversion  0   ee    ee, 3  0   ee,  0 ee   ee,  ee   ee  ’   ee

R. Averbeck, 8 DPG Meeting, Cologne, 3/8/2004 l converter method l add converter of known thickness to experiment l compare e ± spectra with and without converter l separation of e ± from photonic and non- photonic sources e  coincidence method e ± from photonic sources are correlated with a  l separation of e ± from different sources Open charm via single electrons (II) l three independent methods to measure electrons from non- photonic sources!

R. Averbeck, 9 DPG Meeting, Cologne, 3/8/2004 PHENIX PRELIMINARY Open charm in p+p collisions at √s = 200 GeV l non-photonic e ± from p+p collisions at 200 GeV l PYTHIA tuned to lower energy data (√s < 63 GeV) l for p T > 1.5 GeV/c spectra are “harder” than PYTHIA prediction PHENIX PRELIMINARY l reference for nuclear collisions l spectral shape –PYTHIA charm & bottom line shapes with normalizations as independent free parameters l total cross section –PYTHIA describes data at low p T –use PYTHIA to extrapolate to full phase space

R. Averbeck, 10 DPG Meeting, Cologne, 3/8/2004 PHENIX PRELIMINARY Open charm from d+Au collisions at √s NN = 200 GeV l non-photonic e ± from d+Au collisions at 200 GeV l cross section divided by the nuclear overlap integral T AB to account for the difference in system size between p+p and d+Au l very good agreement of d+Au data with the scaled p+p reference within uncertainties l no indication for strong cold-nuclear matter modifications l how about centrality dependence? 1/T AB EdN/dp 3 [mb GeV -2 ]

R. Averbeck, 11 DPG Meeting, Cologne, 3/8/2004 Centrality (in)dependence in d+Au collisions PHENIX PRELIMINARY 1/T AB 1/T AB EdN/dp 3 [mb GeV -2 ]

R. Averbeck, 12 DPG Meeting, Cologne, 3/8/2004 Open charm from Au+Au collisions at √s NN = 200 GeV 1/T AB EdN/dp 3 [mb GeV -2 ] PHENIX l non-photonic e ± from Au+Au collisions at 200 GeV l cross section divided by the nuclear overlap integral TAB to account for the difference in system size between p+p and Au+Au l very good agreement of Au+Au data with the scaled p+p reference within uncertainties up to p T = 1.5 GeV/c l at higher p T more statistics is needed l no indication for strong medium modifications l how about centrality dependence?

R. Averbeck, 13 DPG Meeting, Cologne, 3/8/2004 Centrality (in)dependence in Au+Au collisions 1/T AA 1/T AB EdN/dp 3 [mb GeV -2 ] l more statistics is highly desirable!

R. Averbeck, 14 DPG Meeting, Cologne, 3/8/2004 Binary collision scaling in Au+Au <  < l charm production seems to scale with T AB, i.e. with the number of binary collisions N Coll l 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  is shown as yellow band l binary scaling seems to work!

R. Averbeck, 15 DPG Meeting, Cologne, 3/8/2004 PHENIX PRELIMINARY Does charm flow in Au+Au? l charm flow could indicate partonic flow, i.e. collectivity on the parton level l v 2 measures the 2 nd harmonic of the Fourier expansion of the azimuthal distribution of particle emission with respect to the reaction plane l v 2 of e ± from non- photonic sources is related to charm v 2 ! l uncertainties are too large to make a definite statement!

R. Averbeck, 16 DPG Meeting, Cologne, 3/8/2004 Summary (I): open charm at RHIC l PHENIX: inclusive electrons in p+p, d+Au, and Au+Au at √s NN = 200 GeV l yield of electrons from non-photonic sources l consistent with binary scaling l no indication for strong enhancement / suppression of charm cross section in nuclear collisions l statistics limited regarding l presence of spectral modifications in Au+Au (energy loss)? l charm flow in Au+Au? l to be answered by Run-4 data (currently ongoing) charm data as baseline for J/  measurements!

R. Averbeck, 17 DPG Meeting, Cologne, 3/8/2004 How to identify J/  (example: 200 GeV) J/  →e + e - l J/y→  +  - (north  -arm) l subtraction of combinatorial background by subtraction of like-sign dilepton mass spectra from unlike-sign spectra l (small) physical background remains +-+- ±±±±

R. Averbeck, 18 DPG Meeting, Cologne, 3/8/2004 J/  suppression/enhancement in Au+Au at RHIC? l 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 GeV! taking data !~400+2x1600 ? first J/  observation at RHIC l first sizeable samples in p+p & d+Au

R. Averbeck, 19 DPG Meeting, Cologne, 3/8/2004 X1X1 X2X2 J/  in North y > 0 X1X1 X2X2 J/  in South y < 0 rapidity y Example of predicted “gluon shadowing” in d+Au gluons in Pb / gluons in p X Anti Shadowing J /    +  - Analysis for d+Au & p+p North Muon ArmSouth Muon Arm d Au Central Arm From Eskola, Kolhinen, Vogt: Nucl. Phys. A696 (2001) J/  mostly produced by gluon fusion → sensitive to gluon pdf l three rapidity ranges probe different momentum fractions x 2 of Au partons l South (y < -1.2) : large X 2 (in gold) ~ l Central (y ~ 0) : intermediate X 2 ~ l North (y > 1.2) : small X 2 (in gold) ~ l (anti)shadowing ↔ (enhancement) depletion of (high) low momentum partons

R. Averbeck, 20 DPG Meeting, Cologne, 3/8/2004 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) l similar to measurements at lower energy (E866: √s = 39 GeV)

R. Averbeck, 21 DPG Meeting, Cologne, 3/8/2004 BR  pp = 160 nb ± 8.5 % (fit) ± 12.3% (abs) - preliminary J/  J /  cross section versus rapidity

R. Averbeck, 22 DPG Meeting, Cologne, 3/8/2004 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 l data indicate nuclear effects (difficult to disentangle)! l weak shadowing l weak absorption

R. Averbeck, 23 DPG Meeting, Cologne, 3/8/2004 High x 2 ~ 0.09 Low x 2 ~ R cp (central / peripheral) versus N coll l define four centrality classes for d+Au collisions l determine N coll for each class in a Glauber model l calculate R cp l low and medium x 2 l weak nuclear effects l small (shadowing) centrality dep. l high x 2 l steep rise with centrality l how can antishadowing rise so steeply while shadowing does not? l final state effect in Au remnants (close to Au frame)?

R. Averbeck, 24 DPG Meeting, Cologne, 3/8/2004 Summary (II): J/  at RHIC l cold nuclear matter effects have been observed in d+Au collisions l weak gluon shadowing l weak absorption l p T broadening: similar to lower energy data l disentangling these effects requires more data modest baseline for J/  measurements in Au+Au collisions is available: the stage is set! l Run-4 (Au+Au at 200 GeV) is currently ongoing! l smaller than expected from lower energy data

R. Averbeck, 25 DPG Meeting, Cologne, 3/8/2004 Outlook J/  production in Au+Au at 200 GeV (Run-4) a first J/  signal in the dielectron channel l stay tuned!

R. Averbeck, 26 DPG Meeting, Cologne, 3/8/2004 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 *as of January Countries; 58 Institutions; 480 Participants* The PHENIX Collaboration