Exploring the Quark-Gluon Plasma at RHIC & LHC Today s Perspective

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1 Exploring the Quark-Gluon Plasma at RHIC & LHC Today s Perspective

2 Modifications to α s heavy quark-antiquark coupling at finite T from lattice QCD O.Kaczmarek, hep-lat/ Constituents - Hadrons, dressed quarks, quasi-hadrons, resonances? Coupling strength varies investigates (de-)confinement, hadronization, & intermediate objects. high Q 2 low Q 2

Nobel Prize 2005 Modifications to α s heavy quark-antiquark coupling at finite T from lattice QCD O.Kaczmarek, hep-lat/0503017 D. Gross H.D. Politzer F.

3 Nobel Prize 2005 Modifications to α s heavy quark-antiquark coupling at finite T from lattice QCD O.Kaczmarek, hep-lat/ D. Gross H.D. Politzer F. Wilczek QCD Asymptotic Freedom (1973) Constituents - Hadrons, dressed quarks, quasi-hadrons, resonances? Coupling strength varies investigates (de-)confinement, hadronization, & intermediate objects. 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. high Q 2 low Q David Gross, Nobel Lecture (RMP 05) 2

4 Early universe Phase Diagram of QCD Matter see: Alford, Rajagopal, Reddy, Wilczek Phys. Rev. D64 (2001) Temperature T c ~ 170 MeV LHC RHIC Critical point? quark-gluon plasma hadron gas color superconductor nucleon gas nuclei Neutron stars CFL vacuum ρ 0 baryon density

5 Quark-Gluon Plasma Plasma (Soup) Standard Model Lattice Gauge Calculations predict QCD Deconfinement phase transition at T c ~ 175 MeV (ε c ~ 0.5 GeV / fm 3 ) 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?)

Ultra-Relativistic Heavy Ion Collisions Interaction of Au nuclei complete in τ few tenths fm/c Gold nucleus diameter = 14 fm γ = 100 (Lorenz contracted) τ = (14 fm/c) / γ

6 Ultra-Relativistic Heavy Ion Collisions Interaction of Au nuclei complete in τ few tenths fm/c Gold nucleus diameter = 14 fm γ = 100 (Lorenz contracted) τ = (14 fm/c) / γ ~ 0.1 fm/c General Orientation Hadron (baryons, mesons) masses ~ 1 GeV Hadron sizes ~ meters (1 fm 1 fermi) RHIC Collisions E cm = 200 GeV/nn-pair Total E cm = 40 TeV

7 Ultra-Relativistic Heavy Ion Collision at RHIC

8 On the First Day (at RHIC) Initial Observations: dn ch /dη PHOBOS Large produced particle multiplicities 400 ed. - less than expected! gluon-saturation? 200 dn ch /dη η=0 = 670, N total ~ 7500 CGC? 0 > 15,000 q + q in final state, > 92% are produced quarks Au + Au 200 GeV 130 GeV 19.6 GeV η Large energy densities (dn/dη, de T /dη) ε 5 GeV/fm 3 ε 5 15 ε critical x nuclear density PHENIX 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

9 How do RHIC Collisions Evolve? 1) Superposition of independent p+p: momenta random relative to reaction plane Reaction plane b r

10 How do RHIC Collisions Evolve? 1) Superposition of independent p+p: momenta random relative to reaction plane High density pressure at center 2) Evolution as a bulk system Pressure gradients (larger in-plane) push bulk out flow more, faster particles seen in-plane b r zero pressure in surrounding vacuum

11 Azimuthal Angular Distributions 1) Superposition of independent p+p: momenta random relative to reaction plane N 2) Evolution as a bulk system Pressure gradients (larger in-plane) push bulk out flow N 0 π/4 π/2 3π/4 π φ-ψ RP (rad) more, faster particles seen in-plane 0 π/4 π/2 3π/4 π φ-ψ RP (rad)

12 1 On the First Day at RHIC - Azimuthal Distributions STAR, PRL (2003) b 6.5 fm b 4 fm midcentral central collisions Top view Beams-eye view

1 On the First Day at RHIC - Azimuthal Distributions STAR, PRL90 032301

13 1 On the First Day at RHIC - Azimuthal Distributions STAR, PRL (2003) b 10 fm b 6.5 fm b 4 fm peripheral collisions Top view Beams-eye view

.. x Mass dependence of v 2 Requires - Early thermalization (0.

14 y 1 z Elliptic Flow Saturates Hydrodynamic Limit Azimuthal asymmetry of charged particles: dn/dφ ~ v 2 (p T ) cos (2 φ) +... x Mass dependence of v 2 Requires - Early thermalization (0.6 fm/c) curves = hydrodynamic flow zero viscosity, Tc = 165 MeV Ideal hydrodynamics (zero viscosity) nearly perfect fluid ε ~ 25 GeV/fm 3 ( >> ε critical ) Quark-Gluon Equ. of State

pattern is observed for identified hadrons

level, it is predicted to be simple KE T

15 Identified Hadron Elliptic Flow Complicated Complicated v 2 (p T ) flow pattern is observed for identified hadrons d 2 n/dp T dφ ~ v 2 (p T ) cos (2 φ) Baryons quarks flow collectively Mesons If the flow established at quark level, it is predicted to be simple KE T KE T / n q, v 2 v 2 / n q, n q = (2, 3 quarks) for (meson, baryon)

16 If baryons and mesons form from independently flowing quarks then quarks are deconfined for a brief moment (~ s), then hadronization!

17 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

AdS 5 /CFT a 5D Correspondence of 4D Systems Analogy between black hole physics and equilibrium thermodynamics Solutions possess hydrodynamic characteristics Similar to fluids viscosity, diffusion

18 AdS 5 /CFT a 5D Correspondence of 4D Systems Analogy between black hole physics and equilibrium thermodynamics Solutions possess hydrodynamic characteristics Similar to fluids viscosity, diffusion constants,. MULTIPLICITY Entropy Black Hole Surface Area Use strongly coupled DISSIPATION N = 4 SUSY YM theory. Viscosity Graviton Absorption Derive a quantum lower viscosity bound: η/s > 1/4π our world dim brane horizon (the bulk) Extra dimension

Ultra-low (Shear)Viscosity Fluids 4π η/s η/s (water) >10 η/s (limit) = 1/4π QGP T = 2 x 10 12 K Quantum lower viscosity bound: η/s > 1/4π

19 Ultra-low (Shear)Viscosity Fluids 4π η/s η/s (water) >10 η/s (limit) = 1/4π QGP T = 2 x K Quantum lower viscosity bound: η/s > 1/4π (Kovtun, Son, Starinets) From strongly coupled N = 4 SUSY YM theory. 2-d Rel Hydro describes STAR v 2 data with η/s 0.1 near lower bound!

20 The RHIC fluid may be the least viscous fluid ever seen The American Institute of Physics announced the RHIC quark-gluon liquid as the top physics story of 2005! see

equilibrium abundances universal hadronization temperature Small net baryon

21 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) μ B ~ MeV Chemical Freezeout Conditions T = 177 MeV, μ B = 29 MeV T ~ T critical (QCD)

22 Particles are thermally distributed and flow collectively, at universal hadronization temperature T = 177 MeV!

23 On the Second Day (~ Year) at RHIC Probing Hot QCD Matter with Hard-Scattered Probes leading particle hadrons hadrons leading particle parton energy loss: modification of jets and leading particles & jet-correlations

24 High Momentum Hadrons Suppressed - Photons Not dev Deviations from binary scaling of hard collisions: R N π / γ AA AA = π / γ NcollNpp Photons Hadrons factor 4 5 suppression

25 Dynamical Origin of High p T Hadron Suppression? How does parton lose energy? What happens to the radiation? ε E q ~ μ Λ What is the dependence on the type of parton? For collisional energy loss what about recoil energy? ΔE gluon > ΔE quark, m=0 > ΔE quark, m>0 One parameterization of energy loss q ^ = μ 2 / Λ

26 q^ Parameterization of Parton Energy Loss Eskola, Honkanen, Salgado, Wiedemann Nucl Phys A747 (2005) 511 q ~ μ Λ q ^ = 5 15 GeV 2 / fm from RHIC R AA Data

27 Interpretation of the Parton Energy Loss Energy loss requires large qˆ GeV /fm 5-15 (also : Dainese, Loizides, Paic, hep-ph/ ) RHIC data sqgp q ~ μ Λ QGP Pion gas Cold nuclear matter R. Baier, Nucl Phys A715, 209c

28 Heavy Quark Suppression Using fixed order next-toleading log (FONL) cross sections for charm and beauty Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637:362, 2006 Insufficient suppression from theoretical models!

29 AdS 5 /CFT Again! - Initial Results on Jet Quenching from J. J. Friess, S. S. Gubser and G. Michalogiorgakis,arXiv:hep-th/ H. Liu, K. Rajagopal and U. A. Wiedemann, arxiv:hep-ph/ , recent PRL

30 Hard Scattering (Jets) as a Probe of Dense Matter II STAR p + p jet event Jet STAR event Au+Au in e + e (jet?) collision event Can we see jets in high energy Au+Au?

31 dev Jet correlations in proton-proton reactions. Strong back-toback peaks. Where Does the Energy Go? Azimuthal Angular Correlations

32 dev Jet correlations in central Gold-Gold. Away side jet disappears for particles p T > 2 GeV Where Does the Energy Go? Azimuthal Angular Correlations

Müller Mach cone from sonic boom? H. Stoecker J. Casalderrey-Solana & E.

33 Where Does the Energy Go? dev Jet correlations in central Gold-Gold. Away side jet reappears in particles p T > 200 MeV 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!

A Near-side Ridge Appears! Di-hadron correlations Near-side ridge Trigger jet Trigger Jet (near-side) η Near-side ridge Au+Au 0-10% preliminary 3 < p t,trigger < 4 GeV p t,assoc. > 2 GeV J.

34 A Near-side Ridge Appears! Di-hadron correlations Near-side ridge Trigger jet Trigger Jet (near-side) η Near-side ridge Au+Au 0-10% preliminary 3 < p t,trigger < 4 GeV p t,assoc. > 2 GeV J. Putschke, STAR, QM 2006 Jets: scale with # of binary collisions Ridge: exists to highest p T (trig) correlated with jets But ridge spectra same as medium ( bulk-like, seen for mesons/baryons) John Harris thermal (Yale) spectra + flow origin? Hadron or jet-heating? 07 - Frascati, Italy, 8-13 Oct. 2007

Possible Ridge Mechanisms So Far References to proposed explanations so far: Radiated gluons, broadened by Longitudinal flow, Armesto et al, PRL 93 (2004) Color magnetic fields, Majumder et al,

35 Possible Ridge Mechanisms So Far References to proposed explanations so far: Radiated gluons, broadened by Longitudinal flow, Armesto et al, PRL 93 (2004) Color magnetic fields, Majumder et al, hep-ph/ Medium heating + recombination, Chiu & Hwa PRC72, Radial flow + trigger particle bias, Voloshin nucl-th/ , N.P. A749, 287 Initial parton scatter + Jet-medium interactions, C.Y. Wong, hep-ph/

36 The suppression of high p T hadrons and the quenching of jets indicates the presence of a high density, strongly-coupled colored medium.!

37 Conclusions about a QGP at RHIC (for reference) Large ε > ε c (T > T c ) 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 ~ T c (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 p T hadrons, away-side jet quenched Large opacity (energy loss) extreme gluon/energy densities strongly-interacting QGP (sqgp)

38 Future!

39 Geneva with Large Hadron Collider Superimposed Starts in Spring 2008

40 Simple Expectations - Heavy Ion Physics at the LHC s NN (GeV) factor 28 t form (fm/c) T / T c ε (GeV/fm 3 ) τ QGP (fm/c) SPS RHIC LHC 0.1 shorter hotter denser > 10 longerlived Significant increase in hard scattering yields at LHC: - jets & large p T processes - σ bb (LHC ) ~ 100 σ bb (RHIC) - σ cc (LHC) ~ 10 σ cc (RHIC)

41 The Future of RHI s at the LHC: Dedicated HI experiment - ALICE Two pp experiments with HI program: ATLAS and CMS

42 Size: 16 x 26 meters Weight: 10,000 tons HMPID TOF TRD PMD ITS Muon Arm PHOS TPC ALICE Set-up

43 A View of ALICE Before Detector Installation

45 So far at RHIC: R AA The Quark-Gluon Plasma at RHIC & LHC Today s Perspective! Elliptic Flow Near-perfect Fluid High p T Suppression Strongly-coupled QGP d 2 N AA dydp T d 2 N pp!!! AA dydp T N coll!! Jet Quenching Strongly-coupled QGP Away-side of jet Energy dissipation/propagation in medium Medium properties? Near-side Ridge!!!! Something new, unresolved Heating of the system Longitudinal expansion? Initial parton distributions? Initial parton bremsstrahlung + flow? RHIC and LHC: Cover 2 3 decades of energy ( s NN ~ 20 GeV 5.5 TeV) What are the properties of hot QCD in this temperature range (T ~ MeV)?

At LHC: R AA The Quark-Gluon Plasma at RHIC & LHC Today s Perspective Is the QCD phase diagram feature-less at 1 4 T c? What happens as we go up in T (e.g. coupling)? Are there new phenomena?

46 At LHC: R AA The Quark-Gluon Plasma at RHIC & LHC Today s Perspective Is the QCD phase diagram feature-less at 1 4 T c? What happens as we go up in T (e.g. coupling)? Are there new phenomena? d 2 N AA dydp T d 2 N pp AA dydp T N coll What s the range of theoretical validities (non-pqcd, pqcd, strings)? Measure/understand parton energy loss at the fundamental level Establish flavor (gluon and quark mass) dependence Use jets and/or photons to establish hard-scattered parton energy Jet modifications - longitudinal & transverse heating Medium response to jet-heating (near- and away-side) Measure/use open charm and beauty decays (also as jet-tags) cc and bb states (T i, screening/suppression, enhancement?) Direct Photon Radiation? Developments in theory (lattice, hydro, parton E-loss, string theory ) the next frontier!

47 Special Thanks for Contributions to This Presentation!! Miklos Gyulassy Peter Jacobs Mike Lisa Thomas Ullrich Urs Wiedemann

Prospects with Heavy Ions at the LHC

Prospects with Heavy Ions at the LHC The Quark-Gluon Plasma at RHIC & LHC So far at RHIC: Elliptic Flow Near-perfect Fluid High p T Suppression Strongly-coupled QGP R AA! d 2 N AA dydp T d 2 N pp!!! AA