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Selected Results from PHENIX

Selected Results from PHENIX. David Silvermyr, ORNL. Bormio, Jan 23, 2008. Outline. RHIC & PHENIX Highlights Electromagnetic radiation : (some) photon and heavy quark/quarkonia results at RHIC + Recent results/publications & outlook : upcoming results.

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Selected Results from PHENIX

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  1. Selected Results from PHENIX David Silvermyr, ORNL Bormio, Jan 23, 2008

  2. Outline • RHIC & PHENIX Highlights • Electromagnetic radiation : (some) photon and heavy quark/quarkonia results at RHIC + Recent results/publications & outlook : upcoming results All results at √snn = 200 GeV unless explictly stated

  3. The Physics of RHIC • Create very high temperature and density matter • as existed some sec after the Big Bang • inter-hadron distances comparable to that in neutron stars • collide heavy ions to achieve maximum volume • Study the hot, dense medium • do the nuclei dissolve into a quark gluon plasma? • Collide Au + Au ions at high energy • s = 200 GeV/nucleon pair, p+p, d+A, Cu+Cu QGP definition : a new state of matter where the fundamental degrees of freedom are not color-neutral hadrons.

  4. RHIC / Long Island ~ 100km [60 miles] Manhattan Au RHIC/Brookhaven

  5. Hadrons reflect medium properties when inelastic collisions stop (chemical freeze-out). Real and virtual photons from q scattering sensitive to the early stages. Probe also with q and g produced early, & passing through the medium on their way out. History of Heavy Ion Collisions high , pressure builds up ,  e+e-, + Kpnd,

  6. Central arms: hadrons, photons, electrons p > 0.2 GeV/c |y| < 0.35 [70 < q < 110 deg.]  Muon arms: muons at forward rapidity p > 2GeV/c 1.2 < |y| < 2.4 [11 < q < 33 deg.]  Centrality measurement: We use beam beam counters together with zero degree calorimeters The PHENIX detector

  7. EMCAL MuID TOF MuTrk TEC/TRD PCs DC RICH NTC BBC MVD ZDC/SMD FCAL Annotated View [Physics Today]

  8. What is PHENIX? 600+ Collaborators 600+ MByte/s peak 600+ TByte/run (year)

  9. RHIC’s First Major Discoveries • Discovery of strong “elliptic” flow: • Elliptic flow in Au + Au collisions at √sNN= 130 GeV, STAR Collaboration, (K.H. Ackermann et al.). Phys.Rev.Lett.86:402-407,2001 • Discovery of “jet quenching” • Suppression of hadrons with large transverse momentum in central Au+Au collisions at √sNN = 130 GeV, PHENIX Collaboration (K. Adcox et al.), Phys.Rev.Lett.88:022301,2002 Later: heavy quarks (this talk), jet correlation modifications (next talk)..

  10. z y x Result I: Motion Is Hydrodynamic • When does thermalization occur? • Strong evidence that final state bulk behavior reflects the initial state geometry • Because the initial azimuthal asymmetrypersists in the final statedn/df ~ 1 + 2v2(pT) cos (2 f) + ... 2v2

  11. The “Flow” Knows Quarks • The “fine structure” v2(pT) for different mass particles shows good agreement with ideal (“perfect fluid”) hydrodynamics PRL. 98, 162301 (2007)] • Scaling flow parameters by quark content nq resolves meson-baryon separation of final state hadrons baryons mesons

  12. Result II: How one would like to probe the Matter.. Matter we want to study Calibrated Light Meter Calibrated LASER We have to use probes produced in the medium! Calibrated Heat Source

  13. Probing the Medium Sometimesa high energy photon is created in the collision. We expect it to pass through the plasma without pause.

  14. Color Probes of the Medium Sometimeswe produce a high energy quark or gluon. • If the plasma is dense enough we expect the quark or gluon to be “swallowed up” [scattered quarks radiate energy (~ GeV/fm)] • decreases their momentum (fewer high pT particles) • “kills” jet partner on other side

  15. (from quark and gluon jets) Experimental Results Scaling of photons shows excellent calibrated probe. Quarks and gluons disappear into medium, except contributions consistent with surface emission. SurvivalProbability Size of Medium

  16. Part 2: Electromagnetic radiation • Photons • Testing pQCD • Thermal photons • Dileptons, low and intermediate mass region [briefly] • Vector meson modification(?) • Thermal radiation • Heavy quarks; studied via leptons • Open charm and quarkonia resonances

  17. Sources of photons • In A+A collisions • High pT photons (pT > ~6 GeV): non thermal • Initial parton-parton scattering: as in p+p • not affected by dense matter  test the theoretical description of A+A collisions with pQCD • Low pT photons (pT < ~3 GeV) : thermal • Come from the thermalized medium • Carry information about the initial temperature of the QGP • Thermal photons are created in the QGP as well as in the hadron gas over the entire lifetime of these phases  test hydrodynamical models • Low and intermediate pT photons (up to ~6 GeV) • Interaction of the quarks and gluons from the hard scattering processes with the QGP • qhard + gQGP  q + g • g get a large fraction of the momentum of qhard

  18. pQCD photons (high pT) in Au+Au • PHENIX Run 2 • Computing RAA.vs.Npart • Quenched/suppressed p0 • Direct g are not suppressed • PHENIX Run 4 • Reach up to 18 GeV/c (12 GeV for Run 2) • Qualitatively well described by NLO pQCD calculations

  19. Thermal photons (low pT) Central Au+Au run 4 Excess over pQCD observed at pT < 4 GeV/c  Well described including hydrodynamical predictions for thermal photons (QGP + HG) Comparisons with p+p and d+Au in progress. PHENIX preliminary Expect final results (Run4 paper) quite soon..

  20. VECTOR MESONS IN MEDIUM (Low Mass Region) THERMAL DILEPTONS (Intermediate Mass Region) Dileptons

  21. Dileptons : SPS Results • QGP thermal radiation (Intermediate Mass Region) • Expect thermal radiation from hot medium  initial temperature of the QGP • Experimentally, should be accessible in the Intermediate Mass Region • At SPS – CERN (~20 GeV): • Intermediate mass excess observed by NA50 in Pb+Pb • NA60 in In+In  not coming from D decays  prompt dileptons Nucl. Phys. A774, 43 (2006) • Chiral Symmetry Restoration (Low Mass Region) • Experimentally expect mass drop and broadening of the r-meson • At SPS-CERN (~20 GeV), low mass excess observed by CERES in Pb+Au and confirmed by NA60 in In+In.

  22. LMR and IMR at RHIC Cocktail plot low mass region Data below 150 MeV/c² well described by the cocktail Enhancement observed in 150 < mee < 750 MeV; also increases with centrality intermediate mass region Absence of excess with cc correlated PYTHIA distribution But medium effect should randomize the cc correlation  room for thermal radiation Au+Au 200 GeV (run 4); arXiv:0706.3034 22

  23. Heavy quarks / Charm l- Direct reconstruction Difficult without measure of vertex (ct ~120 mm) K+ c K- Indirect reconstruction Measure contribution of semileptonic decays from Heavy flavor to lepton spectra p+

  24. Heavy flavour in p+p PRL98, 192301 (2007) PRL97, 252002 (2006) • Measurements made by both PHENIX and STAR • Difference observed between PHENIX and STAR • FONLL prediction is ~1/2 of PHENIX data but agree with the data within uncertainty • STAR is ~ a factor > 2 larger than PHENIX

  25. Heavy flavour cross section hep-ex/0508034 hep-ex/0609010 • Comparison between STAR and PHENIX cross section results, per binary collision • Same discrepancy observed in Au+Au • FONLL prediction is ~1/2 of PHENIX data but agree with the data within uncertainty • STAR is ~ a factor > 2 larger than PHENIX

  26. Heavy flavour RAA STAR hadrons pT> 6 GeV/c STAR : PRL98, 192301 (2007) PHENIX : PRL98, 172301 (2007) • RAA comparison • Consistent RAA observed between PHENIX and STAR • The difference observed in p+p and Au+Au yields is cancelled out in the ratio.. • Understanding the difference : • Direct D measurement with PHENIX • Low material run with STAR

  27. Heavy flavour RAA PHENIX : PRL98, 172301 (2007) At large pT suppression similar to that of light hadrons! Suggests very high density of produced matter.. Flow (v2) is also similar to light hadrons. => Short relaxation time of heavy quarks, and/or, small diffusion coefficient are required by the data. Model comparison suggest h/s ratio close to quantum lower bound, i.e. near a perfect fluid. .

  28. « if high energy heavy ion collisions lead to the formation of a hot quark-gluon plasma, then color screening prevents cc binding in the deconfined interior of the interaction region …/… it is concluded that J/Y suppression in nuclear collisions should provide an unambigous signature of quark-gluon plasma formation » Quarkonia : J/y July 1997 Mid-central central peripheral SPS results, LHC etc.: C. Lourenco (Fri) ‘Anomalous suppression’ observed in Pb+Pb (NA50) and In+In (NA60) at CERN/SPS

  29. J/Y at RHIC • Production • Main production process : gluon fusion • Feed-down: • ~60% from direct production • ~30% cc J/y + g • ~10% y’  J/y + X • In nuclear matter • Initial state effects • Nuclear shadowing (Cold Nuclear Matter Effect) • pT broadening : Cronin effect (Cold Nuclear Matter Effect) • Final state effects • Absorption in nuclear matter(Cold Nuclear Matter Effect) • Suppression? (Hot and Dense Matter Effect ?) • Experimentally • At RHIC : √s up to 200 GeV (<20 GeV at SPS) • J/y is mainly measured by the PHENIX experiment • Measure J/y in p+p : used as a reference • Measure J/y in d+Au : to study Cold/Normal Nuclear Matter Effects • Measure J/y in Au+Au and Cu+Cu to study hot/dense matter effects

  30. J/Y production in p+p PRL 98, 232002 (2007) J/Y is a rare process  expect in A+A collisions : (sJ/Y)AA <Ncoll>(sJ/Y)pp In the following, again use (if no nuclear effect RAA=1) • To be used as a reference for A+A spp in agreement with Color Octet Model

  31. Au+Au @ RHIC Suppresssion at RHIC  larger suppression observed at forward rapidity in Au+Au, opposite to expectation from screening models! Au+Au PHENIX: PRL98, 232301 (2007)

  32. Cu+Cu @ RHIC Suppresssion at RHIC  Similar suppression in Au+Au and Cu+Cu at same Npart • d+Au : Small absorption, or breakup : mb • Same CNM effects at forward & mid-rapidity? Effects beyond CNM? • need more precise measurement of • CNM effects at RHIC.. arXiv:0711.3917 Cu+Cu PHENIX: arXiv:0801.0220 [submitted New Year’s Eve 2007..]

  33. A+A results - comparison SPS .vs. RHIC • Side Note: Models that reproduce SPS results fail to reproduce RHIC results, unless some recombination is also introduced.. • Including CNM effects • Lack of precision on CNM effects at RHIC •  can’t discriminate between • Same effect beyond CNM at SPS and RHIC or not? •  need more precise measurement of CNM effects at RHIC  need more d+Au data (ongoing 2007/8 Run) Comparison with SPS results  Suppression at RHIC ~ suppression at SPS (at mid-rapidity).  But cold nuclear matter (CNM) effects may be different..

  34. Y(1s) Y(2s) J/y Example: PHENIX Nose Cone Calorimeter c c J/y + g cc Y’ QCD Thermometer Different binding energies have states “melting” at different temperatures. RHIC I AuAu 0.2 nb-1 No detector upgrades No e-cooling RHIC I ++ AuAu 2 nb-1 Detector upgrades No e-cooling RHIC II AuAu 20 nb-1 Detector upgrades Luminosity upgrade w/ e-cooling

  35. Hot Off the Presses.. • “Quantitative Constraints on the Opacity of Hot Partonic Matter from Semi-Inclusive Single High Transverse Momentum Pion Suppression in Au+Au collisions at sqrt(s_NN) = 200 GeV” arXiv:0801.1665 Constraint method: data vs model parameter => dNg/dy ~= 1400 +- 200; <qhat> ~= 13 +- 3 GeV2/fm [errors are asymmetric]

  36. More : Example – jets/correlations See following talk. . [PHENIX and STAR each have ~70 refereed publications..] ‘Famous’ paper: Phys. Rev. Lett. 97, 052301 (2006) (157 citations by last week) Related: nucl-ex/0408007 , arXiv:0712.3033, nucl-ex/0611019, arXiv:0705.3238 ..

  37. Summary & Outlook • We probe extreme QCD and create an interesting state of matter at RHIC! Many exciting properties to understand: Viscosity limits, how can equilibration be so rapid? [AdS/CFT links?] Jet quenching effects; energy loss limits? Are starting to get more quantitative.. Temperature limits from direct/thermal photons(?) Heavy quark physics: J/y recombination or not? [Doesn’t melt in the first place?] Do J/y also flow..? We’ve come a long way in the last few years; a lot of new interesting results are sure to follow in the coming years – also very active upgrade program underway at RHIC

  38. EXTRA / BACKUP

  39. J/Y : Interpretations All models for y=0 Satz Capella Rapp PRL98, 232301 (2007) PRL 92, 212301 (2004) Eur. Phys. J C43, 97 (2005) PRL97, 232301 (2006) PRC 69, 054903 (2004) NPA789, 334 (2007) • Models including anomalous suppression only • Which reproduce SPS data, • Predict too much suppression • Color screening + CNM (1 mb) • Comovers + CNM (1 & 3 mb) • Direct production + CNM • Adding recombination • Recombination c+c -> J/Y + g • NJ/Y Ncc² • Compensate direct suppression • Need better open charm measurement to better constraint recombination • Measure J/Y flow to check recombination

  40. pT Broadening(?) Flat, or rather modest, broadening observed.. PHENIX: arXiv:0801.0220

  41. Ncharged, ET exhibit the Nuclear Geometry Define centrality classes: ZDC vs BBC Extract N participants: Glauber model ET EZDC b QBBC Nch PHENIX PHENIX Nch ET

  42. Colliding system expands: Energy  to beam direction per unit velocity || to beam Lattice ec pR2 2ct0 Energy Density eBj ~ 23.0 GeV/fm3 eBj ~ 4.6 GeV/fm3 2ct Lattice Critical Density Energy density far above transition value predicted by lattice. • With realistic estimates of t0 , eBj • eBj >= 15 GeV/fm3 [nucl-ex/0410003; PHENIX WP]

  43. Particle Ratios; Freeze-Out Info Blackbody spectrum Ni/Nj Ratio of Yields T=177 MeV μB=29 MeV Braun-Munzinger, Magestro, Stachel (2001)

  44. Like a Perfect Fluid? First time hydrodynamics without any viscosity describes heavy ion reactions. v2 pT (GeV) Thermalization time t=0.6 fm/c and e=20 GeV/fm3 *viscosity = resistance of liquid to shear forces (and hence to flow)

  45. Jet correlations in proton-proton reactions. Strong back-to-back peaks. Jet correlations in central Gold-Gold. Away side jet disappears for particles pT > 2 GeV Jet correlations in central Gold-Gold. Away side jet reappears for particles pT>200 MeV Jet Quenching! Azimuthal Angular Correlations

  46. LMR and IMR at RHIC Au+Au 200 GeV (run 4) Measured by PHENIX Measures di-electrons 8.108 Min Bias events large background at low mass (S/B ~ 1/200 @ 0.5 GeV) Background subtracted by event mixing technique checking background subtraction (converter run) use a subset of data (5.107 events) taken with additional material around the beam pipe increase background by a factor ~ 2.5 Results agree with statistical errors Jan 2 - 13, 2008 F. Fleuret - LLR Ecole Polytechnique, France WHEPP X, Chennai

  47. CNM effects @ RHIC – J/Y in d+Au d Au rapidity Central South North arXiv:0711.3917 X1 > X2(~0.003) X1 ~ X2(~0.02) X1 < X2(~0.09) J/ South y < 0 J/ North y > 0 J/ Central y ~ 0 • PHENIX data compatible with : • Weak gluon shadowing • Small absorption, or breakup : mb • Need more precise d+Au data (ongoing Run8..)

  48. References / Links Results from first few years at RHIC summarized in White Papers from each experirment: PHENIX WP: NPA 757 http://arxiv.org/abs/nucl-ex/0410003 PHENIX Publications: http://www.phenix.bnl.gov/WWW/talk/pub_papers.php American Inst. Of Physics; Top Physics Story of 2005: http://www.aip.org/pnu/2005/split/757-1.html

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