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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


  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