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Have we found the Quark Gluon Plasma at RHIC? Experimental evaluation by the PHENIX Collab.

Have we found the Quark Gluon Plasma at RHIC? Experimental evaluation by the PHENIX Collab. M. J. Tannenbaum Brookhaven National Laboratory Upton, NY 11973 USA. PHENIX Collaboration. See nucl-ex/0410003. Seminar, ETH Zurich October 19, 2004.

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Have we found the Quark Gluon Plasma at RHIC? Experimental evaluation by the PHENIX Collab.

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  1. Have we found the Quark Gluon Plasma at RHIC? Experimental evaluation by the PHENIX Collab. M. J. Tannenbaum Brookhaven National Laboratory Upton, NY 11973 USA PHENIX Collaboration See nucl-ex/0410003 Seminar, ETH Zurich October 19, 2004 MJT-Seminar-ETHZ-Oct 2004

  2. High Energy Nucleus-Collisions provide the means of creating Nuclear Matter in conditions of Extreme Temperature and Density • At large energy or baryon density, a phase transition is expected from a state of nucleons containing confined quarks and gluons to a state of “deconfined” (from their individual nucleons) quarks and gluons covering a volume that is many units of the confinement length scale. MJT-Seminar-ETHZ-Oct 2004

  3. V= -4 as +  r  -4 as e-(T) 3 r 3 r • The QCD confinement scale---when the string breaks---is order: The Quark Gluon Plasma (QGP) 1/QCD ~1/m=1.4 fm • With increasing temperature, T, in analogy to increasing Q2, s(T) becomes smaller, reducing the binding energy, and the string tension (T) becomes smaller, increasing the confinement radius, effectively screening the potential • For r < 1/ a quark does feel the full color charge but for r >1/ the quark is free of the potential, effectively deconfined MJT-Seminar-ETHZ-Oct 2004

  4. The Quark Gluon Plasma (QGP) • The state should be in chemical (particle type) and thermal equilibrium <pT> ~T • The major problem is to relate the thermodynamic properties, Temperature, energy density, entropy of the QGP or hot nuclear matter to properties that can be measured in the lab. MJT-Seminar-ETHZ-Oct 2004

  5. The gold-plated signature for the QGPJ/ Suppression • In 1986, T. Matsui & H. Satz PL B178, 416 (1987) said that due to the Debye screening of the color potential in a QGP, charmonium production would be suppressed since the cc-bar couldn’t bind. • This is CERN’s claim to fame: but the situation is complicated because J/ are suppressed in p+A collisions. [NA50 collaboration, M.C. Abreu, et al., PLB 477, 28 (2000)] MJT-Seminar-ETHZ-Oct 2004

  6. MJT-Seminar-ETHZ-Oct 2004

  7. MJT-Seminar-ETHZ-Oct 2004

  8. RHIC pC Polarimeters Absolute Polarimeter (H jet) BRAHMS & PP2PP (p) PHOBOS Siberian Snakes Siberian Snakes PHENIX (p) STAR (p) Spin Rotators Spin flipper Partial Siberian Snake Spin Rotators Strong AGS Snake Pol. H- Source LINAC BOOSTER Helical Partial Siberian Snake AGS 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipole AGS pC Polarimeters RHIC: RHI+polarized p-p collider 2  1011 Pol. Protons / Bunch e = 20 p mm mrad MJT-Seminar-ETHZ-Oct 2004

  9. PHENIX=Pioneering HighEnergy NuclearInteractioneXperiment What is PHENIX? A large, multi-purpose nuclear physics experiment at the Relativistic Heavy-Ion Collider (RHIC): 1 A  197. For Au+Au: 19  sNN  200 GeVLmax= 2 x 1026 cm-2 s-1 two independent rings ---> p+Au, d+Au, etc. MJT-Seminar-ETHZ-Oct 2004

  10. How to discover the QGP • The Classical road to success in RHI Physics: J/ Suppression • Major background for e detection is photons and conversions from 0. but more importantly • Need an electron trigger for full J/ detection  EMCal plus electron ID at trigger level. • High pT0 and direct  production and two-particle correlations are the way to measure hard-scattering in RHI collisions where jets can not be detected directly---> segmentation of EMCal must be sufficient to distinguish 0 and direct  up to 25 GeV/c (also vital for spin) • Charm measurement via single e (Discovered by CCRS experiment at CERN ISR) MJT-Seminar-ETHZ-Oct 2004

  11. “Mike, is there a `real collider detector’ at RHIC?---J. Steinberger ” • PHENIX is picturesque because it is not your father’s solenoid collider detector • Special purpose detector designed and built to measure rare processes involving leptons and photons at the highest luminosities. MJT-Seminar-ETHZ-Oct 2004

  12. MuID TOF EMCAL MuTrk TEC/TRD PCs DC RICH NTC BBC MVD ZDC/SMD FCAL Annotated View MJT-Seminar-ETHZ-Oct 2004

  13. All charged tracks ApplyRICH cut h Real Net signal Background (0) • ElectroMagnetic Calorimeter measures Energy of photons and electrons • reconstructs 0 from 2 photons. Measures decent Time of Flight • hadrons deposit Minimum Ionization, or higher if they interact • For electron ID require RICH (cerenkov) and matching energy in EMCal • momentum +TOF=charged particle ID • High Resolution TOF completes the picture giving excellent charged hadron PID • Electron and photon energy can be matched to < 1%--No nonlinearity problem EMC Energy / Momentum Detecting electrons means detecting all particles=PHENIX MJT-Seminar-ETHZ-Oct 2004

  14. PHENIX EMCal Lead-Glass (PbGl) Super Module 6 PbSc sectors (15,552 channels) 2 PbGl sectors (9,216 channels)  = 0.38 = 8  22.50=1800 Lead-Scintillator (PbSc) Module 6 PbSc sectors 2 PbGl sectors PbScSector PbGl Sector BNL/PHENIX separates 0 and direct  up to >25 GeV/c WA80/98 MJT-Seminar-ETHZ-Oct 2004

  15. 2 Central Tracking arms 2 Muon arms Beam-beam counters Zero-degree calorimeters (not seen) The PHENIX detector MJT-Seminar-ETHZ-Oct 2004

  16. Charged particle tracking: • Drift chamber • Pad chambers (MWPC) • Particle ID: • Time-of-flight (hadrons) • Ring Imaging Cherenkov • (electrons) • EMCal (, 0) • Time Expansion Chamber • Acceptance: • || < 0.35 – mid-rapidity •  = 2  90 Detectors in the central spectrometer arms (pseudorapidity |h| < 0.35) • Charged Particle Tracking: • Drift-Chambers (DC) • Pad-Chambers (PC) • Identification of charged hadrons: • Time-of-Flight (TOF) with start signal from the Beam-Beam-Counters (BBC) • Electron Identification • Ring Imaging Cherenkov Detector (RICH) • p0 via p0  gg: • Lead scintillator calorimeter (PbSc) • Lead glass calorimeter (PbGl) MJT-Seminar-ETHZ-Oct 2004

  17. Example of a central Au+Au event at snn =200 GeV MJT-Seminar-ETHZ-Oct 2004

  18. Run Year Species s1/2 [GeV ] Ldt Ntot p-p Equivalent Data Size 01 2000 Au+Au 130 1 mb-1 10M 0.04 pb-13 TB 02 2001/2002 Au+Au 200 24 mb-1 170M 1.0 pb-110 TB p+p 200 0.15 pb-1 3.7G 0.15 pb-1 20 TB 03 2002/2003 d+Au 200 2.74 nb-1 5.5G 1.1 pb-146 TB p+p 200 0.35 pb-1 6.6G 0.35 pb-1 35 TB 04 2003/2004 Au+Au 200 241 mb-1 1.5G 10.0 pb-1 270 TB Au+Au 62 9 mb-1 58M 0.36 pb-1 10 TB Run-1 to Run-4 Capsule History Run-3 Run-1 Run-2 MJT-Seminar-ETHZ-Oct 2004

  19. Schematic Au+Au collision MJT-Seminar-ETHZ-Oct 2004

  20. Spectators Participants Peripheral Central 10-15% • Centrality selection : Sum of Beam-Beam Counter • (BBC, |h|=3~4) and energy of Zero-degree calorimeter (ZDC) • ExtractedNcollandNpartbased on Glauber model. 5-10% 0-5% Collision Centrality Determination MJT-Seminar-ETHZ-Oct 2004

  21. Ncharged, ET exhibit(&could determine) the Nuclear Geometry Define centrality classes: ZDC vs BBC Extract N participants: Glauber model ET EZDC b QBBC Nch PHENIX PHENIX Nch ET MJT-Seminar-ETHZ-Oct 2004

  22. Colliding system expands: Energy  to beam direction per unit velocity || to beam pR2 • e 4.6 GeV/fm3 (130 GeV Au+Au) 5.5 GeV/fm3 (200 GeV Au+Au) 2ct0 well above predicted transition! Is the energy density high enough? PRL87, 052301 (2001) EMCal measures Bj MJT-Seminar-ETHZ-Oct 2004

  23. Spacetime evolution is important MJT-Seminar-ETHZ-Oct 2004

  24. My best bet 1998-after BDMPS MJT-Seminar-ETHZ-Oct 2004

  25. Phys. Rev. 179, 1547 (1969) Phys. Rev. 185, 1975 (1969) Bjorken Scaling in Deeply Inelastic Scattering and the Parton Model---1968 MJT-Seminar-ETHZ-Oct 2004

  26. BBK 1971 S.M.Berman, J.D.Bjorken and J.B.Kogut, Phys. Rev. D4, 3388 (1971) • BBK calculated for p+p collisions, the inclusive reaction • A+B C + Xwhen particle C has pT>> 1 GeV/c • The charged partons of DIS must scatter electromagnetically “which may be viewed as a lower bound on the real cross section at large pT.” MJT-Seminar-ETHZ-Oct 2004

  27. CCR at the CERN-ISRDiscovery of high pT production in p-p F.W. Busser, et al., CERN, Columbia, Rockefeller Collaboration Phys. Lett. 46B, 471 (1973) Bj scaling  BBK scaling • e-6pT breaks to a power law at high pT with characteristic s dependence • Large rate indicates that partons interact strongly (>> EM) with other. • Data follow BBK scaling but with n=8!, not n=4 as expected for QED MJT-Seminar-ETHZ-Oct 2004

  28. BBK scaling with n=8, not 4 Inspires Constituent Interchange Model Berman, Bjorken, Kogut, PRD4, 3388 (1971) xT=2pT/s n=4 for QED or vector gluon n=8 for quark-meson scattering by the exchange of a quark CIM-Blankenbecler, Brodsky, Gunion, Phys.Lett.42B,461(1972) MJT-Seminar-ETHZ-Oct 2004

  29. CCOR 1978--Discovery of “REALLY high pT>7 GeV/c” at ISR CCOR A.L.S. Angelis, et al, Phys.Lett. 79B, 505 (1978) See also A.G. Clark, et al Phys.Lett 74B, 267 (1978) • Agrees with CCR, CCRS (Busser) data for pT < 7 GeV/c. • Disagrees with CCRS fit pT > 7 GeV/c • New fit is: MJT-Seminar-ETHZ-Oct 2004

  30. QCD: Cahalan, Geer, Kogut, Susskind, PRD11, 1199 (1975) n(xT, s) WORKS n5=4++ Same data Ed3/dp3(xT) ln-ln plot MJT-Seminar-ETHZ-Oct 2004

  31. ISR Expt’s more interested in n(xT,s) than absolute cross section Athens BNL CERN Syracuse Collaboration, C.Kourkoumelis, et al Phys.Lett. 84B, 279 (1979) But n(xT,s) agrees cross sections vary by factor of 2 MJT-Seminar-ETHZ-Oct 2004

  32. p-p Thermally-shaped Soft Production Hard Scattering RHIC pp spectra s=200 GeV nicely illustrate hard scattering phenomenology • Good agreement with NLO pQCD • this is no surprise for `old timers’ (like me) since as I just explained, single particle inclusive spectra were what proved QCD in the late 1970’s before jets. • Reference for A+A and p+A spectra • p0 measurement in same experiment allows us the study of nuclear effect with less systematic uncertainties. p0 PHENIX (p+p) PRL 91, 241803 (2003) MJT-Seminar-ETHZ-Oct 2004

  33. -A DIS at AGS (1973)--Hard-Scattering is pointlike MJT-Seminar-ETHZ-Oct 2004

  34. High pT in A+B collisions---TAB Scaling view along beam axis looking down • For point-like processes, the cross section in p+A or A+B collisions compared to p-p is simply proportional to the relative number of pointlike encounters • A for p+A, AB for A+B for the total rate • TAB the overlap integral of the nuclear profile functions, as a function of impact parameter b MJT-Seminar-ETHZ-Oct 2004

  35. The anomalous nuclear enhancement a.k.a. the Cronin effect-- due to multiple scattering of initial nucleons (or constituents) What really Happens for p+A: RA > 1! • Known since 1975 that yields increase as A,  > 1 • J.W. Cronin et al.,Phys. Rev. D11, 3105 (1975) • D. Antreasyan et al.,Phys. Rev. D19, 764 (1979) MJT-Seminar-ETHZ-Oct 2004

  36. The Nuclear Modification Factor RAB is the ratio of pointlike scaling of an A+B measurement to p-p Nuclear Modification Factor: Compare A+B to p-p cross sections AB AB “Nominal effects”: RAB < 1 in regime of soft physics RAB = 1 at high-pT where hard scattering dominates AB AA MJT-Seminar-ETHZ-Oct 2004

  37. High pT physicsPHENIX Year-1 High-pT Hadrons Hadron spectra out to pT~4-5 GeV/c Nominally expect production through hard scattering, scale spectra from N+N by number of binary collisions Peripheral reasonably well reproduced; but central significantly below binary scaling MJT-Seminar-ETHZ-Oct 2004

  38. PHENIX Run-1: RHIC Headline News … January 2002THE major discovery at RHIC (so far) PHENIX PRL 88, 022301 (2002) First observation of large suppression of high pT hadron yields ‘‘Jet Quenching’’? == Quark Gluon Plasma? MJT-Seminar-ETHZ-Oct 2004

  39. Centrality RHIC Run 2 s=200 GeV/c:1) 0extend to higher pT in Au+Au collisions;2) + 0 reference in p-p Au-Au nucl-ex/0304022 Phys. Rev. Letters 91, 072301 (2003) PHENIX MJT-Seminar-ETHZ-Oct 2004

  40. RAA (0) AuAu:pp 200GeVHigh pT Suppression flat from 3 to 10 GeV/c ! Peripheral AuAu - consistent with Ncoll scaling (large systematic error) Binary scaling Factor 5 Large suppression in central AuAu - close to participant scaling at high PT Participant scaling PRL 91, 072301 (2003) MJT-Seminar-ETHZ-Oct 2004

  41. RAA ~ 2.0 A.L.S.Angelis PLB 185, 213 (1987) WA98, EPJ C 23, 225 (2002) PHENIX, PRL 88 022301 (2002) D.d'E. PHENIX Preliminary QM2002 RAA ~1.5 Ncollision scaling Npart scaling RAA ~ 0.4 RAA~0.2 Suppression at RHIC sNN=130 GeV is unique in A+A collisions--Enhancement at lower sNN Cronin Enhancement CERN: Pb+Pb (sNN ~ 17 GeV), a+a (sNN ~31 GeV) plus all previous measurements in p+A in same x range BCMOR Collab. Initial state effect (p+A) only depends on x, final state in A+A could depend on sNN MJT-Seminar-ETHZ-Oct 2004

  42. Suppression: Final State Effect? • Hadronic absorption of fragments: • Gallmeister, et al. PRC67,044905(2003) • Fragments formed inside hadronic medium • Parton recombination (up to moderate pT) • Fries, Muller, Nonaka, Bass nucl-th/0301078 • Lin & Ko, PRL89,202302(2002) • Energy loss of partons in dense matter • Gyulassy, Wang, Vitev, Baier, Wiedemann… See nucl-th/0302077 for a review. MJT-Seminar-ETHZ-Oct 2004

  43. r/ ggg Alternative: Initial Effects • Gluon Saturation • (color glass condensate: CGC) Wave function of low x gluons overlap; the self-coupling gluons fuse, saturating the density of gluons in the initial state. (gets Nch right!) hep-ph/0212316; D. Kharzeev, E. Levin, M. Nardi • Multiple elastic scatterings (Cronin effect) Wang, Kopeliovich, Levai, Accardi • Nuclear shadowing D.Kharzeev et al., PLB 561 (2003) 93 Broaden pT MJT-Seminar-ETHZ-Oct 2004

  44. d+Au: Control Experiment to prove the Au+Au discovery • The “Color Glass Condensate” model predicts the suppression in both Au+Au and d+Au (due to the initial state effect). • The d+Au experiment tells us that the observed hadron suppression at high pT central Au+A is a final state effect. • This diagram also explains why we can’t measure jets directly in Au+Au central collisions: all nucleons participate so charged multiplicity is ~200 times larger than a p-p collision 300 GeV in standard jet cone. d+Au Au+Au = cold medium = hot and dense medium Initial + Final State Effects Initial State Effects Only MJT-Seminar-ETHZ-Oct 2004

  45. Cronin effect observed in d+Au at RHIC sNN=200 GeV, confirms x is a good variable PHENIX preliminary 0 d+Au vs centrality for DNP2003 MJT-Seminar-ETHZ-Oct 2004

  46. This leads to our second PRL cover, our first being the original Au+Au discovery MJT-Seminar-ETHZ-Oct 2004

  47. Theoretical Understanding? Both • Au-Au suppression (I. Vitev and M. Gyulassy, hep-ph/0208108) • d-Au enhancement (I. Vitev, nucl-th/0302002) understood in an approach that combines multiple scattering with absorption in a dense partonic medium  Our high pT probeshave been calibratedand are nowbeing used toexplore the precise propertiesof the medium See nucl-th/0302077 for a review. d-Au Au-Au MJT-Seminar-ETHZ-Oct 2004

  48. Suppression: Final State Effect • Energy loss of partons in dense matter--A medium effect predicted in QCD---Energy loss by colored parton in medium composed of unscreened color charges by gluon bremsstrahlung--LPM radiation • Gyulassy, Wang, Vitev, Baier, Wiedemann… See nucl-th/0302077 for a review. • Baier,Dokshitzer,Mueller, Peigne, Shiff, NPB483, 291(1997),PLB345,277(1995), Baierhep-ph/0209038, • From Vitev nucl-th/0404052: Bj =15 GeV/fm3 MJT-Seminar-ETHZ-Oct 2004

  49. Berman, Bjorken, Kogut, PRD4,3388(1971) QCD: Cahalan, Geer, Kogut, Susskind, PRD11, 1199 (1975) Does the sNN=130, 200 GeV dependence of suppressed 0 follow QCD--xT scaling xT=2pT/s Central 0-10% Peripheral 60 -- 80% MJT-Seminar-ETHZ-Oct 2004

  50. Same data vs xT on log-log plot MJT-Seminar-ETHZ-Oct 2004

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