Partons and jets in a strongly coupled plasma from AdS/CFT Edmond Iancu IPhT Saclay & CNRS Collaboration with Yoshitaka Hatta and Al Mueller (lecture notes arXiv:0812.0500) Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 1
Introduction ■ Experimental results at RHIC suggest that the deconfined hadronic matter (‘Quark–Gluon Plasma’) produced in a Introduction AA collision at high energy might be strongly interacting Outline Motivation ■ A challenge for the theory: lattice QCD cannot be used for Partons and jets in pQCD such dynamical phenomena Hard probes in AdS/CFT Partons from AdS/CFT ■ New method: string theory via AdS/CFT correspondence Jet quenching ◆ not yet QCD: conformal symmetry, no confinement Conclusions Backup ◆ at high energy and/or finite temperature, such issues are (presumably) less important, even in QCD ■ A vigourous activity with many interesting results ◆ conceptually interesting relations between particle physics, string theory, gravity, black holes ◆ physical interpretation of the results is very challenging Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 2
Outline ■ Motivation : Heavy Ion Collisions at RHIC and LHC Introduction Outline ■ Weak coupling: Partons and jets in perturbative QCD Motivation Partons and jets in pQCD ■ Strong coupling: AdS/CFT Correspondence Hard probes in AdS/CFT Partons from AdS/CFT ■ Finite– T plasma: Deep inelastic scattering & Parton Jet quenching saturation Conclusions Backup ■ Finite– T plasma: Jet quenching & Momentum broadening Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 3
The Little Bang ■ Ultrarelativistic heavy ion collisions @ RHIC and LHC Introduction Outline Motivation ● RHIC ● Elliptic flow ● Viscosity/entropy ● Lattice QCD ● Resummations ● Jets in AA Partons and jets in pQCD Hard probes in AdS/CFT ■ Extremely complex phenomena Partons from AdS/CFT Jet quenching ◆ high density partonic systems in the initial wavefunctions Conclusions ◆ multiple interactions during the collisions Backup ◆ complicated, non-equilibrium, dynamics after the collision ◆ expansion, thermalization, hadronisation ■ Is there any place for strong–coupling dynamics ? Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 4
Hadron production at RHIC Introduction Outline Motivation ● RHIC ● Elliptic flow ● Viscosity/entropy ● Lattice QCD ● Resummations ● Jets in AA Partons and jets in pQCD Hard probes in AdS/CFT Partons from AdS/CFT Jet quenching Conclusions Backup ■ ∼ 3000 hadrons in the final state vs. 400 nucleons in AA ■ Most of them arise as hadronized partons ■ Particle correlations are essential to disentangle phenomena Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 5
Elliptic flow at RHIC: The perfect fluid CGC -4 η /s=10 25 STAR non-flow corrected (est). η /s=0.08 Introduction y STAR event-plane 20 Outline Motivation v 2 (percent) 15 ● RHIC ● Elliptic flow ● Viscosity/entropy φ η /s=0.16 10 ● Lattice QCD x ● Resummations ● Jets in AA 5 Partons and jets in pQCD η /s=0.24 Hard probes in AdS/CFT 0 0 1 2 3 4 Partons from AdS/CFT p T [GeV] Jet quenching ■ Non–central AA collision: Pressure gradient is larger along x Conclusions Backup d N d φ ∝ 1 + 2 v 2 cos 2 φ , v 2 = “elliptic flow” ■ Well described by hydrodynamical calculations with very small viscosity/entropy ratio: “perfect fluid” Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 6
Viscosity over entropy density ratio ■ Viscosity/entropy density ratio at RHIC (in units of � ) η Introduction s = 0 . 1 ± 0 . 1(theor) ± 0 . 08(exp) [ � ] Outline Motivation ● RHIC ■ Weakly interacting systems have η/s ≫ � ● Elliptic flow ● Viscosity/entropy ● Lattice QCD ■ Kinetic theory: viscosity is due to collisions among molecules ● Resummations ● Jets in AA Partons and jets in pQCD η ∼ ρ v ℓ = mass density × velocity × mean free path Hard probes in AdS/CFT � �� � Partons from AdS/CFT ∼ 1 /g 4 Jet quenching Conclusions ■ Conjecture (from AdS/CFT) : [Kovtun, Son, Starinets, 2003] Backup η � s ≥ [lower limit = infinite coupling] 4 π ■ The RHIC value is at most a few times � / 4 π ! Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 7
Heating QCD : Lattice results ■ Energy density as a function of T (Bielefeld Coll.) Introduction 16 ε SB /T 4 RHIC Outline ε /T 4 14 Motivation ● RHIC 12 ● Elliptic flow ● Viscosity/entropy 10 ● Lattice QCD LHC ● Resummations 8 ● Jets in AA SPS 3 flavour Partons and jets in pQCD 6 2 flavour ‘‘2+1-flavour’’ Hard probes in AdS/CFT 4 T c = (173 +/- 15) MeV Partons from AdS/CFT 2 ε c ~ 0.7 GeV/fm 3 T [MeV] Jet quenching 0 Conclusions 100 200 300 400 500 600 Backup E / E 0 ≈ 0 . 85 T = 3 T c for ■ Is this deviation from ideal gas small ? Or is it large ? ■ AdS/CFT : E / E 0 → 3 / 4 when λ → ∞ ( N = 4 SYM) Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 8
Finite– T : Resummed perturbation theory ■ This ratio p/p 0 ≈ 0 . 85 can be also explained by resummed perturbation theory Introduction (collective phenomena: screening, thermal masses) Outline (J.-P . Blaizot, A. Rebhan, E. Iancu, 2000) Motivation ● RHIC ● Elliptic flow 1.8 ● Viscosity/entropy ● Lattice QCD p/T 4 1.6 HTL ● Resummations ● Jets in AA 1.4 Partons and jets in pQCD 1.2 Hard probes in AdS/CFT 1.0 (1x1) (1x2) Partons from AdS/CFT 0.8 RG Jet quenching 0.6 Conclusions 0.4 Backup 0.2 T/T c 0.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 ■ First principle calculation without free parameter Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 9
Jets in proton–proton collisions ) Introduction φ d+Au FTPC-Au 0-20% ∆ jet Outline 0.2 ) dN/d( φ p+p min. bias ∆ Motivation dN/d( ● RHIC Au+Au Central ● Elliptic flow TRIGGER ● Viscosity/entropy ● Lattice QCD Trigger 0.1 ● Resummations ● Jets in AA 1/N 1/N Partons and jets in pQCD Hard probes in AdS/CFT 0 Partons from AdS/CFT jet Jet quenching -1 0 1 2 3 4 ∆ φ Conclusions (radians) Backup ■ Azimuthal correlations between the produced jets: a peak at ∆Φ = 180 ◦ Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 10
Nucleus–nucleus collision ) φ d+Au FTPC-Au 0-20% ∆ Introduction 0.2 dN/d( ) φ p+p min. bias ∆ Outline dN/d( Motivation Au+Au Central TRIGGER ● RHIC ● Elliptic flow Trigger 0.1 ● Viscosity/entropy ● Lattice QCD 1/N ● Resummations 1/N ● Jets in AA 0 Partons and jets in pQCD Hard probes in AdS/CFT -1 0 1 2 3 4 Partons from AdS/CFT ∆ φ . (radians) Jet quenching Conclusions ■ The “away–side” jet has disappeared ! Backup absorbtion (or energy loss, or “jet quenching”) in the medium ■ The matter produced in a heavy ion collision is opaque high density, strong interactions, ... or both Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 11
e + e − annihilation: Jets in pQCD ■ How would a high–energy jet interact in a strongly coupled plasma ? Introduction Outline ■ How to produce jets in the first place ? Motivation ■ Guidance from perturbative QCD: e + e − → γ ∗ → q ¯ q Partons and jets in pQCD ● e+e- ● Bremsstrahlung ● Jets q e + ● 3-jet ● DIS * ● F2 ● Parton evolution ● Gluons at RHIC ● Saturation _ 2 Q = s Hard probes in AdS/CFT e − q Partons from AdS/CFT Jet quenching Conclusions ■ Decay of a time–like photon: Q 2 ≡ q µ q µ = s > 0 Backup Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 12
e + e − annihilation: Jets in pQCD ■ How would a high–energy jet interact in a strongly coupled plasma ? Introduction Outline ■ How to produce jets in the first place ? Motivation ■ Guidance from perturbative QCD: e + e − → γ ∗ → q ¯ q Partons and jets in pQCD ● e+e- ● Bremsstrahlung ● Jets ● 3-jet e + ● DIS ● F2 * ● Parton evolution ● Gluons at RHIC ● Saturation Hard probes in AdS/CFT e− Partons from AdS/CFT Jet quenching Conclusions Backup ■ The structure of the final state is determined by ◆ parton branching & hadronisation Laboratoire de Physique Corpusculaire de Clermont-Ferrand, 20 mars 2009 Partons and jets in a strongly coupled plasma from AdS/CFT - p. 13
Recommend
More recommend
