A strongly coupled view of the quark gluon plasma Jorge Casalderrey-Solana
QCD Matters A new phase: Quark Gluon Plasma • Filled the universe μ s after Big Bang • Colour is liberated • A gas of quark and gluons “phase transition” What are the properties of the T c T c ≈ 2 × 10 12 K plasma close to the transition? ≈ 170 MeV Hadron Gas • Colour is confined • Hadrons re-scatter Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 2
Equation of State Wuppertal-Budapest Col. arXiv: 1007.2580 Rapid cross over transition: • Deconfined matter • Chiraly restored matter Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 3
A Gas of Quarks and Gluons At T>10 4 GeV: 1 1 1 ≪ ≪ T gT g 2 T inter-particle Interaction mean free spacing range path Resummations can extend the validity of perturbative methods to much lower temperatures! Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 4
What is the correct picture of the plasma? At T~0.2 GeV α s =0.3 ⟹ g=2 T~gT~g 2 T Is it a system without long lived excitations? Is it a system without quasiparticles? Is it a gas of quark and gluons? Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 5
Heavy Ion Collisions at the LHC ➤ Up to 400 participating nucleons ➤ About 20.000 particles ➤ E T ∼ 1 GeV per particles ➤ Very large initial energy density ετ ~ 16 GeV/(fm 2 c) Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 6
The Little Bang Very strong collective e ff ects ๏ Emission of 20.000 particles correlated with the impact parameter {4-particle cumulant method} 10-20% 0.25 20-30% 30-40% 10-20% (STAR) 0.2 20-30% (STAR) ๏ Correlation measured in 30-40% (STAR) 0.15 terms of Fourier coe ffi cients 0.1 ALICE 0.05 2 v 0 1 2 3 4 5 ๏ Hydrodynamic explosion p (GeV/ c ) t The quark gluon plasma is a very good fluid J. Bernhard, J.S. Moreland, S. Bass, J. Liu, U. Heinz arXiv:1605.03954 Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 7
Implication of η /s Value ๏ It is the smallest value ever measured in any substance. The Quark Gluon Plasma is the most perfect fluid! ๏ It is incompatible with quasiparticles Boltzmann equation ⇒ ๏ It was predicted in 2001 (Policastro, Son, Starients) η 1 = =0.08 s 4 π ... but for a large class of non-abelian gauge theories at infinite coupling via holography Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 8
QFT with no Quasi Particles ๏ This all may be a remarkable coincidence Di ff erent theories, di ff erent matter content, di ff erent symmetries... ๏ But there is certain degree of universality Some properties are the same in all theories with holographic duals Despite: Di ff erent theories, di ff erent matter content, di ff erent symmetries... ๏ All those strongly coupled theories have plasmas with no quasi particles Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 9
Holography • Gauge Theories in the limit Gauge/String Duality, Hot QCD and Heavy Ion Collisions Casalderrey-Solana, Liu, Mateos, Rajagopal and Wiedemann Gauge/String Duality, Heavy ion collision experiments recreating the quark–gluon plasma that fj lled the microseconds-old universe have established that it is a nearly perfect liquid that fm ows with such minimal dissipation that it cannot be seen as made of particles. String theory provides a powerful toolbox for studying matter with such properties. Hot QCD and λ =g 2 N c → ∞ This book provides a comprehensive introduction to gauge/string duality and its applications to the study of the thermal and transport properties of quark–gluon plasma, the dynamics of how it forms, the hydrodynamics of how it fm ows, and its response to probes including jets and quarkonium mesons. Heavy Ion Collisions Calculations are discussed in the context of data from RHIC and LHC and results from fj nite temperature lattice QCD. The book is an ideal reference for students and researchers in string theory, quantum fj eld theory, quantum many-body physics, heavy ion physics, and lattice QCD. Jorge Casalderrey-Solana is a Ramón y Cajal Researcher at the Universitat de Barcelona. His research focuses on the properties of QCD matter produced in ultra- relativistic heavy ion collisions. Hong Liu is an Associate Professor of Physics at MIT. His research interests include quantum gravity and exotic quantum matter. David Mateos is a Professor at the Universitat de Barcelona, where he leads a group working on the connection between string theory and quantum chromodynamics. Krishna Rajagopal is a Professor of Physics at MIT. His research focuses on QCD at high temperature or density, where new understanding can come from unexpected QFT directions. Urs Achim Wiedemann is a Senior Theoretical Physicist at CERN, researching the theory and phenomenology of ultra-relativistic heavy ion collisions. Jorge Casalderrey-Solana, Hong Liu, David Mateos, Krishna Rajagopal T μν Cover illustration: an artist’s impression of the hot T μν matter produced by a heavy ion collision falling into the and Urs Achim Wiedemann black hole that provides its dual description. Created by Mathias Zwygart and inspired by an image, courtesy of the ALICE Collaboration and CERN. 1/Q Holographic Dictionary Direction M Gravity T μν ↔ g μν T ↔ black hole flavor ↔ brane Horizon heavy quark ↔ string J. M. Maldacena, Adv. Theor. Math. Phys 2, 231 (1998) Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 10
Thermalization at Strong Coupling ๏ Simulation of full collision dynamics ➤ Collisions of lump of energies Chesler and Ya ff e 11 JCS, M. Heller, D. Mateos W. van der Schee 13,14 ε∕ρ 4 dual model ρ t shock wave collisions ρ z ๏ Fast onset of hydrodynamics t hydro = 0.63 / T hydro ➤ Hydrodynamics without isotropy Chesler & Yaffe, Wu & Romatschke, Heller, Janik & Witaszczyk, Heller, Mateos, van der Schee, Trancanelli ➤ Hydrodynamics without equation of state Attems, JCS, et. al. 16 Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 11
Microscopic Structure of Plasma ๏ Can we probe the system? e e Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 12
Jets ๏ Energetic Quarks are produced in pairs ๏ Hard process ➤ strong non-abelian bremsstrahlung ➤ Jets: sprays of particles within a fixed resolution R Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 13
Jets as Probes Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 14
Jet Quenching Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 15
Soft Fragment Decorrelation ET1 12 fm ET2<ET1 JCS, Milhano, Wiedemann 10 Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 16
Energy Loss of a Single Quark ๏ Medium Induced gluon bremsstrahlung t 0 t 1 t t 2 t 3 t 4 t 5 BDMPS-Z 96 p (GLV, ASW, AMY, HT ...) k,c (Review: JCS & C. Salgado q 1 ,a 1 q 2 ,a 2 q 3 ,a 3 q 4 ,a 4 q 5 ,a 5 arXiv:0712.3443 ) 1 1 Range of interaction mean free path ⌧ m D λ m . f . p ๏ Non-abelian energy loss: dE dx = 1 q = (mean transferred momentum) 2 m 2 2 ˆ qL D ˆ ⇠ length λ m . f . p Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 17
๏ How do jets loose energy in a system with no quasiparticles? ๏ Holography provides a tool to address this problem Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 18
⇒ Eloss at strong coupling ๏ Heavy Quark ⇔ classical string attached to boundary Heavy (charm) quarks 4 4 2 � TD 2 � TD JCS & Teaney (2006) H. T. Ding et. al 2012 3.5 3.5 Herzong, Karch, Kovtun,Kozcaz, 3 3 Ya ff e (2006) 2.5 2.5 S. Gubser (2006) 2 2 1.5 1.5 1 1 0.5 0.5 T/T c T/T c 0 0 1.4 1.4 1.6 1.6 1.8 1.8 2 2 2.2 2.2 2.4 2.4 2.6 2.6 2.8 2.8 3 3 ๏ Energy loss ⇔ flux of momentum along the string dp Langevin dt = � η D p � ⇥ 1 / 2 1 � 1 . 5 p D ⇥ � � � λ T 3 η D = π 2 π T α sym N � � 2 MT ๏ Compatible with lattice extractions! Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 19
๏ Light Quark ⇔ free end point ๏ Energy loss rate E 1 / 3 x 2 1 dE dx = � 4 1 1 in x stop = T 4 / 3 , x 2 E in q 2 κ sc π x 2 stop � x 2 stop Gubser et al 08, Chesler et al. 08, Ficnar and Gubser 13 Chesler & Rajagopal 14, 15 Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 20
A Hybrid Model • Jet interaction with medium is a multi-scale problem ➤ Hard production (perturbative) ➤ Hard evolutions (perturbative) ➤ Exchanges at medium scale } strong ➤ Soft jet fragments coupling JCS, Gulhan, Milhano, Pablos and Rajagopal 2014, 2015, 2016 • The hybrid approach ➤ Leave jet evolution unmodified (Q>>T) ➤ Each in-medium parton losses energy ➤ We assume that all differences between theories can be packed into one single (fit) parameter Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 21
Observables γ Birmingham Particle Physics Group J. Casalderrey-Solana 07 th June 2017 22
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