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Evidence for a Q u a r k - G l u o n Plasma in Relativistic Heavy Ion Collisions

Evidence for a Q u a r k - G l u o n Plasma in Relativistic Heavy Ion Collisions. Heavy Ions – Results and Interpretation. Nobel Prize 2005. D. Gross. H.D. Politzer. F. Wilczek.

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Evidence for a Q u a r k - G l u o n Plasma in Relativistic Heavy Ion Collisions

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  1. Evidence for aQuark-GluonPlasma in Relativistic Heavy Ion Collisions Heavy Ions – Results and Interpretation John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  2. Nobel Prize 2005 D. Gross H.D. Politzer F. Wilczek “Before [QCD] we could not go back further than 200,000 years after the Big Bang. Today…since QCD simplifies at high energy, we can extrapolate to very early times when nucleons melted…to form a quark-gluon plasma.” David Gross, Nobel Lecture (RMP 05) QCD Asymptotic Freedom (1973) Modifications to s heavy quark-antiquark coupling at finite T from lattice QCD O.Kaczmarek, hep-lat/0503017 Constituents - Hadrons, dressed quarks, quasi-hadrons, resonances? Coupling strength varies investigates (de-)confinement, hadronization, & intermediate objects. low Q2 high Q2 John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  3. Phase Diagram of QCD Matter Early universe see: Alford, Rajagopal, Reddy, Wilczek Phys. Rev. D64 (2001) 074017 LHC quark-gluon plasma RHIC Critical point ? Tc ~ 170 MeV Temperature color superconductor hadron gas nucleon gas nuclei CFL Neutron stars r0 vacuum baryon density John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  4. Quark-Gluon Plasma (Soup) electro- magnetism gravity weak strong Quark-Gluon Plasma • Standard Model Lattice Gauge Calculations • predict QCD Deconfinement phase transition • at Tc ~ 175 MeV (ec ~ 0.5 GeV / fm3) Cosmology Quark-hadron phase transition in early Universe • Can we make the primordial quark-gluon soup in the lab? • Establish properties of QCD at high T (and density?) John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  5. PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS RelativisticHeavy Ion Collider 3.8 km circle v = 0.99995  speed of light John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  6. STAR RelativisticHeavy Ion Collider and Experiments John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  7. p L p K f e jet m g Freeze-out (~ 10 fm/c) Hadronization QGP (~ few fm/c) Hard Scattering + Thermalization (< 1 fm/c) Au Au Space-time Evolution of RHIC Collisions time g e  Expansion  space John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  8. Gold nucleus diameter = 14 fm g = 100 (Lorenz contracted) t = (14 fm/c) / g ~ 0.1 fm/c Ultra-Relativistic Heavy Ion Collisions Interaction of Au nuclei complete in t  few tenths fm/c RHIC Collisions Ecm = 200 GeV/nn-pair Total Ecm = 40 TeV General Orientation Hadron (baryons, mesons) masses ~ 1 GeV Hadron sizes ~ 10-15 meters (1 fm ≡ 1 fermi) John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  9. Ultra-Relativistic Heavy Ion Collision at RHIC John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  10. On the “First Day” (at RHIC) Initial Observations: Large produced particle multiplicities ed. - “less than expected! gluon-saturation?”  dnch/dh |h=0 = 670, Ntotal ~ 7500 > 15,000 q +q in final state, > 92% are produced quarks Au + Au CGC? PHENIX PHOBOS Large energy densities (dn/dh, dET/dh)  e  5 GeV/fm3 e  5 - 15 ecritical 30 - 100 x nuclear density Large collective flow ed. - “completely unexpected!”  Due to large early pressure gradients, energy & gluon densities  Requires hydrodynamics and quark-gluon equation of state Quark flow & coalescence  constituent quark degrees of freedom! 1 John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  11. How do RHIC Collisions Evolve? 1) Superposition of independent p+p: momenta random relative to reaction plane Reaction plane John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  12. more, faster particles seen in-plane How do RHIC Collisions Evolve? 1) Superposition of independent p+p: High density pressure at center momenta random relative to reaction plane 2) Evolution as a bulksystem Pressure gradients (larger in-plane) push bulk “out”  “flow” “zero” pressure in surrounding vacuum John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  13. N N   0 0 /4 /4 /2 /2 3/4 3/4 -RP (rad) -RP (rad) Azimuthal Angular Distributions 1) Superposition of independent p+p: momenta random relative to reaction plane 2) Evolution as a bulksystem Pressure gradients (larger in-plane) push bulk “out”  “flow” more, faster particles seen in-plane John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  14. 1 On the First Day at RHIC - Azimuthal Distributions STAR, PRL90 032301 (2003) b ≈ 6.5 fm b ≈ 4 fm “central” collisions midcentral collisions Top view Beams-eye view John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  15. 1 On the First Day at RHIC - Azimuthal Distributions STAR, PRL90 032301 (2003) b ≈ 10 fm b ≈ 6.5 fm b ≈ 4 fm peripheral collisions Top view Beams-eye view John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  16. 1 z y x curves = hydrodynamic flow zero viscosity, Tc = 165 MeV Elliptic Flow SaturatesHydrodynamic Limit • Azimuthal asymmetryof charged particles: dn/df ~ 1 + 2v2(pT) cos (2 f)+ ... • Mass dependence of v2 • Requires - • Early thermalization • (0.6 fm/c) • Ideal hydrodynamics • (zero viscosity) •  “nearly perfect fluid” • e ~ 25 GeV/fm3 ( >> ecritical ) • Quark-Gluon Equ. of State John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  17. Baryons Mesons Identified Hadron Elliptic Flow Complicated Complicated v2(pT)flow pattern is observed for identified hadrons d2n/dpTdf ~ 1 + 2v2(pT)cos (2 f) 15000 quarks flow collectively If the flow established at quark level, it is predicted to be simple KET KET / nq , v2 v2 / nq , nq = (2, 3 quarks) for (meson, baryon) John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  18. b b Vary System Size to Investigate Viscous Effects Eccentricity: e = <x2 – y2> / <x2 + y2> For perfect hydrodynamics (no viscosity): v2 (pT) / e independent of centrality v2 (pT) / e  PHENIX, nucl-ex/0608033 v2 scales with system size and eccentricity John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  19. large ← impact parameter → small Collision Centrality Dependence of the Flow Fluid: Ideal hydrodynamics Gas: Boltzmann equation • QGP + hadron fluids Overshoot at large impact parameter • QGP fluid and hadron gas Reasonable reproduction Caveat: fluctuation effects • Hadron gas • Undershoot at any impact parameters Impossible to interpret data from hadronic degree of freedom only. T.Hirano, Y.Nara, et al.(’06)‏; M. Isse; M. Gyulassy John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  20. If baryons and mesons formfrom independently flowing quarksthenquarks are deconfined for a brief moment (~ 10 -23 s), then hadronization! John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  21. Universality of Classical Strongly-Coupled Systems? Transport in gases of strongly-coupled atoms RHIC fluid behaves like this – a strongly coupled fluid. Universality of classical strongly-coupled systems?  Atoms, sQGP, ……. AdS/CFT…… K.M. O’Hara et al Science 298 (2002) 2179

  22. Extra dimension (the bulk) AdS5/CFT – a 5D Correspondence of 4D Strongly-Coupled Systems our world - 3 + 1 dim brane • Analogy between black hole physics • and equilibrium thermodynamics • Solutions possess hydrodynamic characteristics • Similar to fluids – viscosity, diffusion constants,…. horizon MULTIPLICITY Entropy  Black Hole Area DISSIPATION Viscosity  Graviton Absorption Use strongly coupled N = 4 SUSY YM theory. Derive a quantum lower viscosity bound: h/s > 1/4p John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  23. h/s (water) >10 h/s (limit) = 1/4p Ultra-low (Shear)Viscosity Fluids 4p h/s QGP T = 2 x 1012 K Quantum lower viscosity bound: h/s > 1/4p (Kovtun, Son, Starinets) From strongly coupled N = 4 SUSY YM theory. 2-d Rel Hydro describes STAR v2 data withh/s  0.1 near lower bound! John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  24. √s = 200 GeV Au + Au What about the Viscosity? Comparing theory and experiment to extract viscosity - D. Teaney  estimate viscous corrections to spectra and elliptic flow using hydrodynamics Gs = 4h/3sT (sound attenuation length) AdS/CFT: Gs/t = 1/(3ptT) ~ 0.11 Need viscous hydrodynamics  a couple of years away…… John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  25. “The RHIC fluid may be theleast viscous fluid ever seen” The American Institute of Physics announced the RHIC quark-gluon liquid as the top physics story of 2005! see http://www.aip.org/pnu/2005/ John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  26. It Flows - Is It Really Thermalized? “Chemical” equilibration (particle yields & ratios): Particles yields represent equilibrium abundances universal hadronization temperature Small net baryon density(K+/K-,B/B ratios) mB ~ 25 - 40 MeV Chemical Freezeout Conditions T = 177 MeV, mB = 29 MeV T ~ Tcritical (QCD) John Harris (Yale) ISSP’06 Erice, Sicily, Italy, 29 Aug – 7 Sep 2006

  27. At RHIC: T = 177 MeV T ~ Tcritical (QCD) QCD Phase Diagram John Harris (Yale) ISSP’06 Erice, Sicily, Italy, 29 Aug – 7 Sep 2006

  28. Particles are thermally distributed and flow collectively,at universal hadronization temperature T = 177 MeV! John Harris (Yale) ISSP’06 Erice, Sicily, Italy, 29 Aug – 7 Sep 2006

  29. leading particle hadrons hadrons leading particle On the “Second” Day (~ Year) at RHICProbing Hot QCD Matter with Hard-Scattered Probes  parton energy loss: modification of jets and leading particles & jet-correlations John Harris (Yale) ISSP’06 Erice, Sicily, Italy, 29 Aug – 7 Sep 2006

  30. High Momentum Hadrons Suppressed - Photons Not Deviations from binary scaling of hard collisions: dev Photons Hadrons factor 4 – 5 suppression John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  31. RHIC data sQGP QGP R. Baier Pion gas Cold nuclear matter pT = 4.5 – 10 GeV/c Much larger energy loss than expected from pQCD Energy Loss of Hard Scattered Parton Energy loss requires large dev (Dainese, Loizides, Paic, hep-ph/0406201) John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  32. H. Liu, K. Rajagopal and U. A. Wiedemann, arXiv:hep-ph/0605178, recent PRL AdS5/CFT Again! - Initial Results on Jet Quenching from J. J. Friess, S. S. Gubser and G. Michalogiorgakis,arXiv:hep-th/0605292. John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  33. RAA of Heavy Quarks from Non-photonic Electrons Suppression observed ~ 0.4-0.6 in 40-80% centrality ~ 0.3 -0.4 in 10-40% ~ 0.2 in 0-5% Max suppression at pT~ 5-6 GeV STAR, nucl-ex/060712 Only c contribution describes RAA but not p + p spectra Theories currently cannot describe the data! Heavy quarks suppressed like light quarks John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  34. Heavy Quark Suppression and Elliptic Flow PHENIX, nucl-ex/0611018 • large suppression & large v2 of electrons → charm thermalization • transport models require • small heavy quark relaxation time • small diffusion coefficient DHQ x (2pT) ~ 4-6 • constrains viscosity/entropy • h/s ~ (1.5 – 3) / 4p • within factor 2 - 3 of conjectured lower quantum bound • consistent with light hadron v2 analysis John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  35. Jet event in e+e-collision STAR Au+Au (jet?) event Hard Scattering (Jets) as a Probe of Dense Matter II STAR p + p  jet event Can we see jets in high energy Au+Au? John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  36. 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 in particles pT > 200 MeV Where Does the Energy Go? dev Color wakes? J. Ruppert & B. Müller Mach cone from sonic boom? H. Stoecker J. Casalderrey-Solana & E. Shuryak Cherenkov-like gluon radiation? I. Dremin A. Majumder, X.-N. Wang Azimuthal Angular Correlations Lost energy of away-side jet is redistributed to rather large angles! John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  37. Response of the Medium 2.5 < pTtrig < 4.0 GeV/c 2.5 < pTtrig < 4.0 GeV/c Measure low-pT associated hadrons • Shapes of jets are modified by the medium • Mach cone? • Cerenkov? • Color wakes? ….. Other…. 1.0 < pTassoc < 2.5 GeV/c 2.0 < pTassoc < 3 GeV/c STAR Preliminary PHENIX preliminary • Properties of the medium can be determined from these shapes! • Sound velocity • Di-electric constant John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  38. hep-ph/0706.0368 Response of the Medium in AdS/CFT v = vs v >> vs Also see: Gubser, Pufu, Yarom, hep-th/0706.0213 John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  39. The suppression of high pT hadrons and the quenching of jets indicates thepresence of a high density, strongly-coupled colored medium. ! John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  40. Hard Scattering Conclusions x Pedestal&flow subtracted High Pt hadrons suppressed in central Au + Au Back-to-back Jets Di-jets in p + p, d + Au (all centralities) Away-side jets quenched in central Au + Au  emission from surface  strongly interacting medium John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  41. Conclusionsabout a QGP at RHIC • Large e > ec (T > Tc) system – QCD vacuum “melts” – NOT hadrons • Thermalized system of quarks and gluons – NOT just q & g scattering • Large elliptic & radial flow fluid flow (“perfect”!) • Heavy quark (charm) flow (not shown) • Particle ratios fit by thermal model T = 177 MeV ~ Tc (lattice QCD) • System governed by quark & gluon Equation of State– NOT hadronic • Flow depends upon particle (constituent quark & gluon) masses • QGP EoS,, quark coalescence • Deconfined system of quarks and gluons – NOT hadrons • Flow already at quark level, charmonium suppression (tbd) • NOT a Weakly-interacting QGP (predicted by Lattice QCD) • Strongly interacting quarks and gluons ….degrees of freedom (tbd) • Strongly-interacting QGP (NOT predicted by Lattice QCD) • Suppression of high pT hadrons, away-side jet quenched • Large opacity (energy loss) extreme gluon/energy densities •  strongly-interacting QGP (sQGP) John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  42. Future! John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  43. The Future of RHI‘s at the LHC: Dedicated HI experiment - ALICE Two pp experiments with HI program: ATLAS and CMS John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  44. SPS RHIC LHC factor 28 5500 √sNN (GeV) 17 200 Significant increase in hard scattering yields at LHC: - jets & large pT processes - sbb (LHC ) ~ 100 sbb (RHIC) - scc (LHC) ~ 10 scc (RHIC) shorter 0.1 tform (fm/c) 1 0.2 3.0 - 4.2 hotter T / Tc 1.1 1.9 15-60 denser e(GeV/fm3) 3 5 > 10 longer-lived tQGP(fm/c) ≤ 2 2-4 Simple Expectations - Heavy Ion Physics at the LHC John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

  45. Explaining the AdS/CFT Equivalence Maldacena’s Conjecture 1) Weakly Coupled (classical) gravity in Anti-deSitter Space (AdS) 2) 3) Strongly Coupled (Conformal) Gauge Field Theories (CFT) John Harris (Yale) QCD – String Theory Meets Collider Physics, DESY 9/28/07

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