Hot and Dense QCD Matter and Heavy-Ion Collisions Ralf Rapp Cyclotron Institute + Physics Department Texas A&M University College Station, USA MLL Colloquium TU Mnchen, 1.) Introduction: Pillars of the Strong Force Stable Matter: u, d, e - m u,d 5-10 MeV But: quarks glued together Confinement proton mass M p = 940 MeV >> 3m q 20 MeV Mass Generation (>95% visible mass) u d u Quantum Chromo Dynamics: strong coupling for Q 0.1fm) QCD vacuum filled by condensates constituent quark mass = g 2 /4 hadrons overlap, quarks liberated Deconfinement (energy density ~ (# d.o.f )T 4, crit 1 GeV / fm 3 ) / T4 / T4 free gas [Cheng et al 08] 1.2 Quark-Gluon Plasma Excite vacuum (hot+dense matter) But: matter around T c strongly coupled: sQGP ( 3p 0 !) - 0|qq|0 condensate melts, m q * 0 Mass Degeneration (hadron masses?) qq T / qq vac - - 3p / T 4 Lattice QCD 08 | | 1.3 QCD Phase Diagram and Nature Early Universe (few s after Big Bang) Compact Stellar Objects (Neutron Stars) Unique opportunity to study: primordial Big Bang matter quark (de-) confinement and mass (de-) generation matter with smallest known viscosity ( /s): near perfect fluid phase structure of non-abelian gauge theory ( string theory!?) 1.) Introduction: QCD and QGP Quark Confinement + Hadron Mass Quark-Gluon Plasma + QCD Phase Diagram 2.) Experimental Probes of QCD Matter Particle Spectra in Heavy-Ion Collisions 3.) Heavy-Quark Probes (c,b) Heavy-Quark Diffusion in the QGP Viscosity?! 4.) Electromagnetic Radiation The Visible Mass in the Universe?! Melting Vector Mesons + Dilepton Spectra 5.) Conclusions Outline 2.1 The Little Bang in the Laboratory Au + Au X e + e - Questions: Thermalization? QGP Signatures?? QGP Properties??? c,b 2.2 Basic Findings at RHIC: Hadron Spectra (1) Ideal Hydrodynamics: p T 2GeV [Shuryak, Heinz, ] v 2 had early thermalization, 0 1fm/c T = 0 T = ( +P) u u P g Input: equation of state (P), initial conditions, freezeout Output: collective flow u radial + elliptic (v 2 ) 2 GeV p T 6 GeV (2) Quark Coalescence: baryon-to-meson anomaly quark-number scaling of elliptic flow [Greco et al 03 Fries et al 03, Hwa et al 03] hadronization via qq M, qqq B (instantaneous, no spatial dependence of v 2 in f q ) _ matter at RHIC thermalizes, 0 > c, small viscosity, partonic E T - m = Ratio 2.3 Problems + Advanced Tools Key Questions: - microscopic origin of near perfect fluid? How perfect? - matter constituents / spectral functions? Heavy Quarks (charm, bottom): created early, Brownian particle traversing QGP fluid transport coefficients thermalization and flow Q-Q bound states (J/ , Y) in QGP? Electromagnetic Emission (photons, dileptons): escape medium unaffected, thermal radiation dilepton invariant mass: (M ee ) 2 = (p e+ +p e ) 2 direct access to in-medium spectral functions - c,b e+ e-e+ e- 1.) Introduction: QCD and QGP Quark Confinement + Hadron Mass Quark-Gluon Plasma + QCD Phase Diagram 2.) Experimental Probes of QCD Matter Particle Spectra in Heavy-Ion Collisions 3.) Heavy-Quark Probes (c,b) Heavy-Quark Diffusion in the QGP Viscosity?! 4.) Electromagnetic Radiation The Visible Mass in the Universe?! Melting Vector Mesons + Dilepton Spectra 5.) Conclusions Outline 3.1 The Virtue of Heavy Quarks (Q=b,c) Large scale m Q >> QCD factorization even at low p T QQ produced in primordial N-N collisions well calibrated initial spectra at all p T Large scale m Q >> T thermal momentum p th 2 = 3m Q T >> T 2 ~ Q 2 therm. mom. transfer Brownian motion (elastic scattering) thermalization delayed by m Q /T memory of rescattering Flavor conserved in hadronization coalescence!? Elastic scattering Q 2 = q 0 2 q 2 ~ (q 2 /2m Q ) 2 q 2 ~ -q 2 quasi-static potential approach!? common framework for heavy-quark diffusion and quarkonia - Brownian Motion: scattering rate diffusion coefficient 3.2 Heavy Quark Diffusion in the QGP Fokker Planck Eq. [Svetitsky 88,] Q pQCD elastic scattering: 1 = therm 20 fm/c slow q,g c Microscopic Calculations of Diffusion [Svetitsky 88, Mustafa et al 98, Molnar et al 04, Zhang et al 04, Hees+RR 04, Teaney+Moore 04] D-/B-resonance model: 1 = therm ~ 5 fm/c c D c _ q _ q parameters: m D, G D [van Hees+RR 04] 3.2.2 Potential Scattering using Lattice QCD potential: use lattice QCD Q-Q internal energy (T>T c ): T-matrix for Q-q scatt. in QGP, G qQ : Q-q propagator HQ potential concept established in vacuum (EFT, lattice) 3-D reduced Bethe-Salpeter Eq. Meson and diquark resonances for T 1.5 T c [Brambilla, Vairo et al] 3.3 Comparison of Drag Coefficients (Thermal Relaxation Rate) proliferation?! NB: pQCD Coulomb AdS/CFT T-matrix: Coulomb + string(latQCD), resummed melting resonances: relax = 1/ ~ 5-8 fm/c ~ constant T [GeV] [1/fm] [Gubser 06] [Peshier 06; Gossiaux+Aichelin 08] [van Hees+RR 04] [van Hees,Mannarelli, Greco+RR 07] 3.4 Heavy Flavor Phenomenology at RHIC Medium Evolution - hydrodynamics or parameterizations thereof - realistic bulk-v 2 (~5-6%) - stop evolution after QGP; hadronic phase? Hadronization - fragmentation: c D + X - coalescence: c + q D, adds momentum and v 2 Semileptonic Electron Decays - D, B e X, ~ conserve v 2 and R AA of parent meson - charm/bottom composition in p-p [Hirano et al 06] relativistic Langevin simulations of heavy quark in QGP: 3.4.2 Model Predictions vs. RHIC Data Semileptonic e Spectra [PHENIX 06] c-q D coalescence increases both R AA and v 2 radiative E-loss upscaled pQCD Langevin with resonances + coalescence Langevin with upscaled pQCD elastic (D s ~ 30/2 T) R AA (dN/dp T ) AA / (dN/dp T ) pp no coal T-Matrix Approach vs. e Spectra at RHIC hadronic resonances at ~T c quark coalescence connects 2 pillars of RHIC! (strong coupl. + coalescence) [van Hees,Mannarelli,Greco+RR 07] Spatial Diffusion D s = T/(m Q 3.5 Viscosity in sQGP? Conjectured bound of sCFT (string-theo. methods): use heavy-quark diffusion to estimate for QGP: kinetic theory: s n tr /s = 1/5 T D s sCFT: s D s = 1/2 T D s close to T c [Kovtun,Son +Starinets 05] [Lacey et al 06] [RR+van Hees 08] 3.6 Reinterpretation of Quark Coalescence Resonance Recombination Model: resonance scattering q+q M close to T c using Boltzmann eq. - [Ravagli et al 08] conserves energy, recovers thermal equilibrium, encodes v 2 (x) in f q (x,p) Langevin, interaction strength determines v 2 max 7% approximate scaling in K T =E T -m Quarks Mesons 2 1.) Introduction: QCD and QGP Quark Confinement + Hadron Mass Quark-Gluon Plasma + QCD Phase Diagram 2.) Experimental Probes of QCD Matter Particle Spectra in Heavy-Ion Collisions 3.) Heavy-Quark Probes (c,b) Heavy-Quark Diffusion in the QGP Viscosity?! 4.) Electromagnetic Radiation The Visible Mass in the Universe?! Melting Vector Mesons + Dilepton Spectra 5.) Conclusions Outline 4.) Electromagnetic Radiation EM Correlation Function: e+ e-e+ e- Im em (M,q; B,T) Dilepton Sources: Relevance: - Quark-Gluon Plasma: high mass + temp. qq e + e , M > 1.5GeV, T >T c - Hot + Dense Hadron Gas: M 1 GeV e + e , T T c - qqqq _ e+ee+e e+ee+e Im em ~ Im D > > B *,a 1,K 1... N, ,K 4.2 -Meson in Medium: Hadronic Interactions D (M,q; B,T) = [M 2 - m 2 - - B - M ] -1 -Propagator: [Chanfray et al, Herrmann et al, RR et al, Weise et al, Koch et al, Mosel et al, Eletsky et al, Oset et al, Lutz et al ] = B, M = Selfenergies: Constraints: decays: B,M N, scattering: N N, A, B / [RR,Wambach et al 99] Meson Melting Switch off Baryons 4.3 Dilepton Excess Spectra at SPS average (T~150MeV) ~ MeV (T~T c ) 600 MeV m fireball lifetime: FB ~ (6.51) fm/c [van Hees+RR 06, Dusling et al 06, Ruppert et al 07, Bratkovskaya et al 08] Thermal Emission Spectrum: 4.3.2 NA60 Data vs. In-Medium Dimuon Rates acceptance-corrected data directly reflect thermal rates! M [GeV] [RR,Wambach et al 99] [van Hees +RR 07] 4.3.3 Low-Mass Dileptons at RHIC: PHENIX Successful approach at SPS fails at RHIC 5.) Conclusions Strong-Interaction (QCD) Matter - Quark (de-) confinement, Mass (de-) generation - Can be studied in heavy-ion collisions - Near perfect liquid?! (Some) Recent Developments - non-perturbative heavy-quark diffusion above T c (QGP liquid) - -resonance melts toward T c (hadron liquid) Upcoming Experimental Programs: - LHC (CERN), RHIC-2 (BNL), FAIR (GSI), NICA (Dubna), - perturbative QGP at high T? - 1 st order transition at finite B > 0? 3.2.3 AdS/CFT-QCD Correspondence [Gubser 07] match energy density (d.o.f = 120 vs. ~40) and coupling constant (heavy-quark potential) to QCD 3-momentum independent [Herzog et al, Gubser 06] (4-2 fm/c) -1 at T= MeV Lat-QCD T QCD ~ 250 MeV But: Higgs Mechanism in Strong Interactions: qq attraction Bose condensate fills QCD vacuum Spontaneous Chiral Symmetry Breaking 3.1 Chiral Symmetry + QCD Vacuum : isospin + chiral (left/right-handed) invariant > > > > qLqL qRqR qLqL - qRqR - - Profound Consequences: effective quark-mass: mass generation massless Goldstone bosons 0,, pion pole-strength f = 93MeV chiral partners split, M 0.5GeV: J P =0 1 1/2 Weinberg Sum Rule(s) Hadron Spectra + Chiral Symm. Breaking Axial-/Vector Correlators pQCD cont. Data: lattice [Bowman et al 02] Theory: Instanton Model [Diakonov+Petrov; Shuryak 85] chiral breaking: |q 2 | 1 GeV 2 Constituent Quark Mass 3.2.2 Dilepton Rates: Hadronic vs. QGP dR ee /dM 2 ~ d 3 q f B (q 0 ;T) Im em Hard-Thermal-Loop [Braaten et al 90] enhanced over Born rate Hadronic and QGP rates degenerate around ~T c Quark-Hadron Duality at all M ?! ( degenerate axialvector SF!) [qqee] [HTL] - Relativistic Langevin simulations for heavy quarks in QGP fireball 4.2 Heavy-Quark Spectra in Au-Au at RHIC [van Hees,Greco+RR 05] Nuclear Modification Factor factor 3-4 stronger effects due to resonance interactions bottom quarks little affected Elliptic Flow R AA (spec) AA /(spec) pp 4.4 Heavy-Light Quark T-Matrix in QGP lattice-QCD based quark potentials F QQ =U QQ T S QQ meson + diquark resonances up to ~1.5 T c [van Hees et al 08] 3.2 EM Spectral Function in Vacuum R = (e + e hadrons) / (e + e ) ~ Im em (M) Im em ~ [Im D + Im D /10 + Im D /5] M 1 GeV: non-perturbative (vector-meson resonance) M > 1.5 GeV: perturbative (qq continuum) Im em ~ N c (e q ) 2 Low-mass dilepton rate: -meson dominated! Im D s=M - e+e-e+e- e+e-e+e- qqqq - R 3.4 Meson in Cold Nuclear Matter + A e + e X e+ ee+ e Nuclear Photo-Production: invariant mass spectra [Riek et al 08] Theoretical Approach: M ee [GeV] Fe - Ti N 0.5 0 N elementary production amplitude in-medium spectral function + [CLAS/JLab 08] well tested at high energies, Q 2 > 1 GeV 2 : perturbation theory ( s = g 2 /4 1.6GeV T 0 =205MeV suff., HG dom. addtl meson-Bremsstrahlung K K substantial at low q t [Liu+ RR05] WA98 Low-q t Anomaly [Turbide,RR+Gale04] thermal radiation q t