1. Quark Matter at High Density/Temperature James Dunlop ICHEP041 Quark Matter at High Density/Temperature James C Dunlop Brookhaven National Laboratory

2. Quark Matter at High Density/Temperature James Dunlop ICHEP042 QGP  a (locally) thermally equilibrated state of matter in which quarks and gluons are deconfined from hadrons, so that color degrees of freedom become manifest over nuclear, rather than merely nucleonic, volumes. M. Gyulassy & L. McLerran Approximately thermalized matter at energy densities so large that the simple degrees of freedom are quarks and gluons. This energy density is that predicted by LGT for the existence of a QGP,  2 GeV/fm 3. Defining the question Recent Definition from STAR for the Quark Gluon Plasma Contrast with other recent definition:

3. Quark Matter at High Density/Temperature James Dunlop ICHEP043 RHIC Implementation Flexibility is key to understanding complicated systems –Polarized protons, sqrt(s) = 50-500 GeV –Nuclei from d to Au, sqrt(s NN ) = 20-200 GeV Physics runs to date –Au+Au @20,62,130,200 GeV –Polarized p+p @200 GeV –d+Au @ 200 GeV PHENIX BRAHMS &PP2PPPHOBOS STAR 1.2 km RHIC

4. Quark Matter at High Density/Temperature James Dunlop ICHEP044 RHIC Experiments Four experiments, two large, two small: STAR: Large acceptance (  PHENIX: Electron/muon identification, high rate trigger, limited acceptance (  central arm) PHOBOS: Tabletop: limited tracking acceptance, largest multiplicity acceptance of all experiments BRAHMS: Forward tracking in classical spectrometer

5. Quark Matter at High Density/Temperature James Dunlop ICHEP045 in entropy density, hence pressure in heavy-quark screening mass in chiral condensate The most realistic calcs.  no discontinuities in thermodynamic proper- ties @ RHIC conditions (i.e., no 1 st - or 2 nd -order phase transition), but still crossover transition with rapid evolution vs. temperature near T c  160 – 170 MeV. Lattice QCD Predicts a RAPID Transition

6. Quark Matter at High Density/Temperature James Dunlop ICHEP046 No exp’tal smoking gun!  Rely on theory-exp’t comparison Charged particle pseudo- rapidity density HBT parameters p T -integrated elliptic flow p T -integrated elliptic flow, scaled by initial spatial eccentricity But only smooth behavior is observed

7. Quark Matter at High Density/Temperature James Dunlop ICHEP047  p T -integrated yield ratios in central Au+Au collisions consistent with Grand Canonical stat. distribution @ T ch = (160 ± 10) MeV,  B  25 MeV, across u, d and s sectors (  s consistent with 1.0).  Inferred T ch consistent with T crit (LQCD)  T 0 =~ T crit.  Does result point to thermodynamic and chemical equilibration, and not just phase-space dominance? Also works in e + e -, p+p Strangeness Enhancement Resonances STAR O PHENIX Chemical Equilibration? Hadron Yield Ratios

8. Quark Matter at High Density/Temperature James Dunlop ICHEP048 Collective Behavior: Azimuthal Anisotropy v 2 y x pypy pxpx coordinate-space-anisotropy  momentum-space-anisotropy Pressure converts initial coordinate-space Anisotropy into final momentum-space anisotropy

9. Quark Matter at High Density/Temperature James Dunlop ICHEP049 Time evolution in Ideal Hydrodynamics Elliptic Flow reduces spatial anisotropy -> shuts itself off Sensitive to EARLY TIMES

10. Quark Matter at High Density/Temperature James Dunlop ICHEP0410 Elliptic flow with ultracold trapped Li6 atoms, a=> infinity regime The system is extremely dilute, but can be put into a hydro regime, with an elliptic flow, if it is specially tuned into a strong coupling regime via the so called Feshbach resonance Extremely cold system at T=10 nK or 10^(-12) eV can produce micro-bang Analogy to Ultracold Atoms Analogy pointed out by Shuryak

11. Quark Matter at High Density/Temperature James Dunlop ICHEP0411 Hydro calculations: Kolb, Heinz and Huovinen v 2 vs. Ideal Hydrodynamics Ideal hydrodynamics reproduces v 2 relatively well –Below p T ~2 GeV, matches v 2 and spectra to ~20-30% Appealing picture: –Nearly perfect fluid with local thermal equilibrium established at <~1 fm with a soft equation of state containing a QGP stage STAR Preliminary

12. Quark Matter at High Density/Temperature James Dunlop ICHEP0412 Score board: status of hydrodynamic models Hadronic + QGP hydro reproduces features of v2( p T ) of , K, p Require early thermalization (  therm 10 GeV/fm 3 Detailed discrepancies between models and with experiment Source average Table courtesy of PHENIX

13. Quark Matter at High Density/Temperature James Dunlop ICHEP0413 P. Kolb, J. Sollfrank, and U. Heinz, Phys. Rev. C. C62 054909 (2000). Sharp freezeout  dip Hydro+RQMD  no dip? Teaney, Lauret & Shuryak Hydro vs. STAR HBT R out /R side How does sensitivity to EOS in hydro calcs. compare quantitatively to sensitiv- ity to other unknown features: e.g., freezeout treatment (compare figures at right), thermaliz’n time, longitudinal boost non-invariance, viscosity?  What has to be changed to understand HBT (below), and what effect will that change have on soft EOS conclusion? How unique and robust is hydro account in detail?

14. Quark Matter at High Density/Temperature James Dunlop ICHEP0414 Partonic energy loss in dense matter: “Jet Tomography” Multiple soft interactions: Strong dependence of energy loss on gluon density  glue  measure   color charge density at early hot, dense phase Gluon bremsstrahlung Opacity expansion: Bjorken, Baier, Dokshitzer, Mueller, Pegne, Schiff, Gyulassy, Levai, Vitev, Zhakarov, Wang, Wang, Salgado, Wiedemann,…

15. Quark Matter at High Density/Temperature James Dunlop ICHEP0415 Partonic energy loss via leading hadrons - Energy loss  softening of fragmentation  suppression of leading hadron yield Binary collision scalingp+p reference

16. Quark Matter at High Density/Temperature James Dunlop ICHEP0416 Control system: p+p collisions p-p PRL 91 (2003) 241803 Good agreement with NLO pQCD Parton distribution functions Fragmentation functions 00  0 well described by pQCD and usual fragmentation functions To generalize for nuclei: f a/N (x a,Q 2,r)  f a/N (x a,Q 2 ). S a/A (x a,r). t A (r) Nuclear modification to structure function (shadowing, saturation, etc.) Nuclear thickness function

17. Quark Matter at High Density/Temperature James Dunlop ICHEP0417 Suppression of inclusive hadron yield central Au+Au collisions: factor ~4-5 suppression p T >5 GeV/c: suppression ~ independent of p T PRL 91, 172302 Au+Au relative to p+p Au+Au central/peripheral R AA R CP

18. Quark Matter at High Density/Temperature James Dunlop ICHEP0418 pQCD in Au+Au? Direct photons [ w/ the real  suppression] (  pQCD x N coll ) /  background Vogelsang/CTEQ6 [if there were no  suppression] (  pQCD x N coll ) / (  background x N coll ) Au+Au 200 GeV/A: 10% most central collisions [   ] measured / [   ] background =  measured /  background Preliminary Perturbative calculation for direct photons works in central Au+Au p T (GeV/c)

19. Quark Matter at High Density/Temperature James Dunlop ICHEP0419  0 R AA  s Systematics Cronin  and parton energy loss  at lower  s Vitev, nucl-th/0404052 Reasonable agreement with 62.4 GeV result. larger Cronin effect gluon dN/dy = 850 (rather than 1100) No large surprises in energy dependence PHENIX Preliminary

20. Quark Matter at High Density/Temperature James Dunlop ICHEP0420 Jets at RHIC p+p  jet+jet (STAR@RHIC) Au+Au  ??? (STAR@RHIC) nucleon parton jet Find this……….in this

21. Quark Matter at High Density/Temperature James Dunlop ICHEP0421 Jets and two-particle azimuthal distributions p+p  dijet trigger: highest p T track, p T >4 GeV/c  distribution: 2 GeV/c<p T <p T trigger normalize to number of triggers trigger Phys Rev Lett 90, 082302

22. Quark Matter at High Density/Temperature James Dunlop ICHEP0422 Azimuthal distributions in Au+Au Au+Au peripheral Au+Au central Near-side: peripheral and central Au+Au similar to p+p Strong suppression of back-to-back correlations in central Au+Au pedestal and flow subtracted Phys Rev Lett 90, 082302 ?

23. Quark Matter at High Density/Temperature James Dunlop ICHEP0423 “Real” tomography: geometry of medium  Au+Au: Away-side suppression is larger in the out-of- plane direction compared to in-plane  Geometry of dense medium imprints itself on correlations STAR Preliminary, nucl-ex/0407007 ?

24. Quark Matter at High Density/Temperature James Dunlop ICHEP0424  Inclusive hadron and away-side cor- relation suppression in central Au+Au, but not in d+Au, clearly establish jet quenching as final-state phenomenon, indicating very strong interactions of hard-scattered partons or their fragments with dense, dissipative medium produced in central Au+Au. PHENIX Hard Sector: Quantitative Indication of Early Gluon Density

25. Quark Matter at High Density/Temperature James Dunlop ICHEP0425  pQCD parton energy loss fits to observed central suppression  dN gluon /dy ~ 1000 at start of rapid expansion, i.e., ~30-50 times cold nuclear matter gluon density.  Large extrapolation needed to take into account time-dependent expansion  How sensitive is this result to:  assumptions of factorization in-medium and vacuum fragmentation following degradation  treatments of expansion and initial-state cold energy loss preceding hard collision? Questions for Parton Energy Loss Models

26. Quark Matter at High Density/Temperature James Dunlop ICHEP0426  s NN = 130 GeV Au+Au  Does the high initial gluon density inferred from parton E loss fits demand a deconfined initial state? Can QCD illuminate the initial conditions?  Assuming initial state dominated by g+g below the saturation scale (con- strained by HERA e-p), Color Glass Condensate approaches ~account for RHIC bulk rapidity densities  dN g /dy ~ consistent with parton E loss.  Rapidity dependence of R dA consistent, though questions about uniqueness  Remaining questions about robustness and uniqueness of approach Gluon Saturation: a QCD Scale for Initial Gluon Density + Early Thermaliz’n Mechanism? BRAHMS, nucl-ex/0403005 PHOBOS, PRC 65, 061901R

27. Quark Matter at High Density/Temperature James Dunlop ICHEP0427 Unusual behavior in baryons Large enhancement in baryons at intermediate p T Not explainable in vacuum fragmentation framework

28. Quark Matter at High Density/Temperature James Dunlop ICHEP0428 Intermediate p T : hints of relevant degrees of freedom Clear separation into two classes: baryons and mesons Apparent scaling with number of constituent quarks in final-state hadron Explained currently by recombination/coalescence of constituent quarks at hadronization If better established, direct evidence of the degrees of freedom relevant at hadronization, and the existence of collective flow at the constituent quark level v 2 /n q STAR Preliminary, nucl-ex/0403032

29. Quark Matter at High Density/Temperature James Dunlop ICHEP0429 jet partner equally likely for trigger baryons & mesons Same side: slight decrease with centrality for baryons Larger partner probability than pp, dAu Away side: partner rate as in p+p confirms jet source of baryons! “disappearance” of away- side jet for both baryons and mesons Jet-like correlations at intermediate p T PHENIX Preliminary, nucl-ex/0408007

30. Quark Matter at High Density/Temperature James Dunlop ICHEP0430  Can one account simultaneously for spectra, v 2 and di-hadron  correlations at intermediate p T with mixture of quark recombination and fragmentation contributions? Do observed jet-like near-side correlations arise from small vacuum fragmentation component, or from “fast-slow” recombination?  Are thermal recomb., “fast-slow” recomb. and vacuum fragment- ation treatments compatible? Double-counting, mixing d.o.f., etc.? Duke-model recomb. calcs. Questions for Coalescence Models

31. Quark Matter at High Density/Temperature James Dunlop ICHEP0431 …suggest appealing QGP-based picture of RHIC collision evolution, BUT invoke 5 distinct models, each with own ambiguities, to get there. pQCD parton E loss Ideal hydro Quark recombination  constituent q d.o.f. CGC Statistical model Early thermalization + soft EOS Very high inferred initial gluon density Very high anticipated initial gluon density u, d, s equil- ibration near T crit Five Observations

32. Quark Matter at High Density/Temperature James Dunlop ICHEP0432 RHIC has made major advances in runs 1-3, leading to an appealing picture of bulk, dense, highly interacting matter. 1)Extended reach in energy density appears to reach simplifying conditions in central collisions -- ~ideal fluid expansion; approx. local thermal equilibrium. 2)Extended reach in p T gives probes for behavior difficult to access at lower energies – jet quenching; ~constituent quark scaling. However: In the absence of a direct “smoking gun” signal of deconfinement revealed by experiment alone, a QGP discovery claim must rest on the comparison with a promising, but still not yet mature, theoretical framework. In this circumstance, clear predictive power with quantitative assessments of theoretical uncertainties are necessary for the present appealing picture to survive as a lasting one. Summary