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A strongly coupled view of the quark gluon plasma Jorge Casalderrey-Solana QCD Matters A new phase: Quark Gluon Plasma Filled the universe s after Big Bang Colour is liberated A gas of quark and gluons phase transition

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A strongly coupled view of the quark gluon plasma

Jorge Casalderrey-Solana

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

QCD Matters

  • Colour is liberated
  • Filled the universe μs after Big Bang

A new phase: Quark Gluon Plasma Hadron Gas

  • Colour is confined
  • Hadrons re-scatter

Tc “phase transition” Tc ≈ 2×1012 K ≈ 170 MeV What are the properties of the plasma close to the transition?

  • A gas of quark and gluons

2

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Equation of State

3

Wuppertal-Budapest Col. arXiv: 1007.2580

Rapid cross over transition:

  • Deconfined matter
  • Chiraly restored matter
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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

A Gas of Quarks and Gluons

4

At T>104 GeV:

≪

T 1 gT 1

≪

g2T 1

inter-particle spacing Interaction range mean free path Resummations can extend the validity of perturbative methods to much lower temperatures!

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SLIDE 5

Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

What is the correct picture of the plasma?

αs=0.3⟹g=2

5

T~gT~g2T

At T~0.2 GeV Is it a gas of quark and gluons? Is it a system without long lived excitations? Is it a system without quasiparticles?

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Heavy Ion Collisions at the LHC

6

➤ About 20.000 particles ➤ Up to 400 participating nucleons ➤ ET ∼1 GeV per particles ➤ Very large initial energy density

ετ ~ 16 GeV/(fm2c)

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

The Little Bang

7

Very strong collective effects

๏ Emission of 20.000 particles correlated

with the impact parameter

The quark gluon plasma is a very good fluid

๏ Hydrodynamic explosion ๏ Correlation measured in

terms of Fourier coefficients

) c (GeV/

t

p

1 2 3 4 5

{4-particle cumulant method}

2

v

0.05 0.1 0.15 0.2 0.25

10-20% 20-30% 30-40% 10-20% (STAR) 20-30% (STAR) 30-40% (STAR)

ALICE

  • J. Bernhard, J.S. Moreland, S. Bass, J. Liu, U. Heinz arXiv:1605.03954
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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Implication of η/s Value

8

๏ It is the smallest value ever measured in any substance.

The Quark Gluon Plasma is the most perfect fluid!

๏ It was predicted in 2001 (Policastro, Son, Starients)

= =0.08

4π 1 s

η

... but for a large class of non-abelian gauge theories at infinite coupling via holography

๏ It is incompatible with quasiparticles

Boltzmann equation ⇒

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

QFT with no Quasi Particles

9

๏ This all may be a remarkable coincidence

Different theories, different matter content, different symmetries...

๏ But there is certain degree of universality

Some properties are the same in all theories with holographic duals Different theories, different matter content, different symmetries... Despite:

๏ All those strongly coupled theories

have plasmas with no quasi particles

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Holography

10

Holographic Direction

1/Q

Tμν Tμν QFT Gravity Horizon

Dictionary

Tμν↔ gμν

heavy quark↔ string

M

T↔ black hole λ=g2Nc→∞

Gauge/String Duality, Hot QCD and Heavy Ion Collisions

Casalderrey-Solana, Liu, Mateos, Rajagopal and Wiedemann Gauge/String Duality, Hot QCD and Heavy Ion Collisions Jorge Casalderrey-Solana, Hong Liu, David Mateos, Krishna Rajagopal and Urs Achim Wiedemann Heavy ion collision experiments recreating the quark–gluon plasma that fjlled the microseconds-old universe have established that it is a nearly perfect liquid that fmows 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. 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 fmows, and its response to probes including jets and quarkonium mesons. Calculations are discussed in the context of data from RHIC and LHC and results from fjnite temperature lattice QCD. The book is an ideal reference for students and researchers in string theory, quantum fjeld 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 directions. Urs Achim Wiedemann is a Senior Theoretical Physicist at CERN, researching the theory and phenomenology of ultra-relativistic heavy ion collisions. Cover illustration: an artist’s impression of the hot matter produced by a heavy ion collision falling into the black hole that provides its dual description. Created by Mathias Zwygart and inspired by an image, courtesy
  • f the ALICE Collaboration and CERN.
  • Gauge Theories in the limit

flavor↔ brane

  • J. M. Maldacena, Adv. Theor. Math. Phys 2, 231 (1998)
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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Thermalization at Strong Coupling

11

ε∕ρ4

ρz

ρt

๏ Simulation of full collision dynamics

➤ Collisions of lump of energies

shock wave collisions

JCS, M. Heller, D. Mateos W. van der Schee 13,14 Chesler and Yaffe 11

๏ Fast onset of hydrodynamics thydro = 0.63 / Thydro

dual model

➤ Hydrodynamics without isotropy ➤ Hydrodynamics without equation of state

Attems, JCS, et. al. 16 Chesler & Yaffe, Wu & Romatschke, Heller, Janik & Witaszczyk, Heller, Mateos, van der Schee, Trancanelli

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Microscopic Structure of Plasma

12

e e

๏ Can we probe the system?

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Jets

13

➤ strong non-abelian bremsstrahlung ➤ Jets: sprays of particles within a fixed resolution R

๏ Energetic Quarks are produced in pairs ๏ Hard process

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Jets as Probes

14

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Jet Quenching

15

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Soft Fragment Decorrelation

16

ET1 ET2<ET1

12 fm

JCS, Milhano, Wiedemann 10

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SLIDE 17

Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Energy Loss of a Single Quark

p k,c q1,a1 q2,a2 q3,a3 q4,a4 q5,a5 t t0 t1 t2 t3 t4 t5

BDMPS-Z 96 (GLV, ASW, AMY, HT ...)

Range of interaction 1 mD ⌧ 1 λm. f. p mean free path

(Review: JCS & C. Salgado arXiv:0712.3443 ) 17

๏ Medium Induced gluon bremsstrahlung

dE dx = 1 2 ˆ qL

ˆ q = (mean transferred momentum)2 length ⇠ m2

D

λm. f. p

๏ Non-abelian energy loss:

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

18

๏ How do jets loose energy in a system

with no quasiparticles?

๏ Holography provides a tool to address

this problem

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Eloss at strong coupling

19

๏ Heavy Quark ⇔ classical string attached to boundary ๏ Energy loss ⇔ flux of momentum along the string

dp dt = ηDp ηD = π p λT 3 2MT

JCS & Teaney (2006)

  • S. Gubser (2006)

Herzong, Karch, Kovtun,Kozcaz, Yaffe (2006)

๏ Compatible with lattice extractions!

D ⇥ 1 2πT

  • 1.5

αsymN ⇥1/2

Langevin

⇒

0.5 1 1.5 2 2.5 3 3.5 4 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 2TD T/Tc 0.5 1 1.5 2 2.5 3 3.5 4 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 2TD T/Tc

  • Heavy (charm) quarks
  • H. T. Ding et. al 2012
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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

20

1 Ein dE dx = 4 π x2 x2

stop

1 q x2

stop x2

xstop = 1 2 κsc E1/3

in

T 4/3 ,

๏ Light Quark ⇔ free end point ๏ Energy loss rate

Chesler & Rajagopal 14, 15 Gubser et al 08, Chesler et al. 08, Ficnar and Gubser 13

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

A Hybrid Model

  • Jet interaction with medium is a multi-scale problem

➤ Hard evolutions (perturbative) ➤ Exchanges at medium scale ➤ Soft jet fragments

strong coupling

}

  • The hybrid approach

➤ Leave jet evolution unmodified (Q>>T) ➤ Each in-medium parton losses energy ➤ Hard production (perturbative)

JCS, Gulhan, Milhano, Pablos and Rajagopal 2014, 2015, 2016

21

➤ We assume that all differences between theories can be packed

into one single (fit) parameter

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Observables

22

γ

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Success of the Hybrid Model

23

0.05 0.1 0.15 0.2 0.25 0.3 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Event Fraction AJ 0 − 10% Centrality Vacuum+Smearing Data Strong Coupling 0.2 0.4 0.6 0.8 1 1.2 100 120 140 160 180 200 220 240 260 280 300 Jet RAA PT (GeV) 0-10% Centrality Strong Coupling Data 0.5 1 1.5 2 30 40 50 60 70 80 90 100 IAA Jet PT 0 − 30% Centrality P jet T > 30 GeV ∆φ > 7π/8 60 < P γ T < 80 GeV Strong Coupling Data 0.2 0.4 0.6 0.8 1 1.2 1.4 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 1 Nγ dNJγ dxJγ xJγ 0 − 10% Centrality P jet T > 30 GeV ∆φ > 7π/8 Strong Coupling Smeared pp Data 0.2 0.4 0.6 0.8 1 40 50 60 70 80 90 100 110 RJγ P γ T 0 − 30% Centrality P jet T > 30 GeV ∆φ > 7π/8 Strong Coupling Smeared pp Data

5 observables 1 fit parameter pT and centrality

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Tested Predictions

24

Core features of the model have been validated by e.g. photon-jet observables predictions

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Medium Back-Reaction

25

Chesler &Yaffe 06

  • The QGP is an extremely good fluid

➤ Medium response to Eloss must be collective ➤ Strong coupling computations provide an explicit example

JCS, Shuryak & Teaney 06

➤ Collectivity starts at short distance 1/T from the jet ➤ There is a strong momentum flux along the jet direction ➤ Essential to understand soft particle distribution around jets.

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Recovering Jet Energy

26 40 30 20 10 10 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 PbPb R=0.3, 0-30% Quenching + Medium Response h/ pk

T i

∆ 8.0-300.0 4.0-8.0 2.0-4.0 1.0-2.0 0.5-1.0 h/ pk

T i∆

CMS

Leading Jet Associated Jet

  • Medium response completely fixed by Eloss

➤ No additional parameters

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Jet Masses

27

from D. Caffarri’s talk on Tue

  • Little sensitivity to strong quenching!

ET1 ET2<ET1

12 fm

➤ Puzzling result ➤ Removing soft fragments ⇒ Jet mass narrowing

0.05 0.1 0.15 0.2 0.25 5 10 15 20 25 0 − 10% R = 0.4 60 < PT, ch jet < 80 GeV Event Fraction Mch jet (GeV) Back No Back pp reference (PYTHIA) ALICE Data R=0.4 0.05 0.1 0.15 0.2 0.25 5 10 15 20 25 0 − 10% R = 0.4 80 < PT, ch jet < 100 GeV Event Fraction Mch jet (GeV) Back No Back pp reference (PYTHIA) ALICE Data R=0.4 0.05 0.1 0.15 0.2 0.25 5 10 15 20 25 0 − 10% R = 0.4 100 < PT, ch jet < 120 GeV Event Fraction Mch jet (GeV) Back No Back pp reference (PYTHIA) ALICE Data R=0.4

Charged jet mass

  • Medium response regenerates the missing mass
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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Not Everything Works: Jet Shapes

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0.05 0.1 0.15 0.2 0.25 0.3 0-10% Centrality 100 < P jet

T

< 300 GeV 0.3 < |η| < 2, r < 0.3 P parton

T

> 1 GeV PbPb/pp r Back No Back CMS Data

R

r

➤ All current models fail in some observable

JCS, Gulhan, Milhano, Pablos and Rajagopal 16

28

  • Jet Narrowing too strong for this observable
  • Overall description of jets is competitive
  • Trash the model?
  • Are there physics missing?
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SLIDE 29

Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Transverse Size Resolution

29

๏ Perturbative analysis of non-abelian classical currents

r⊥

๏ Colour exchanges decorrelate the currents

1 ˆ qL

τcoh = θc θq¯

q

2/3 L θ2

c =

1 ˆ qL3

๏ Coherence is lost at a time ๏ Fragments at small angles cannot be resolved

JCS, Iancu arXiv:1105.1760 Mehtar-Tani, Tywoniuk, Salgado arXiv:1009.2965, 1102.4317 arXiv:1112.5031, 1205.5739

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Quantum Calculation

Interferences

30

๏ Double emission rate off in-medium quark

Hard Vertex Hard Gluon Soft Gluon

τf = 2ω k2⊥ ➤ Confirms the classical calculation on interferences ➤ Supplements time structure of the process

JCS, Pablos and Tywoniuk 16

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SLIDE 31

Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

New Picture for Jet Quenching

  • 0.4 -0.2

0.2 0.4

  • 0.4
  • 0.2

0.2 0.4 5 10 15 20 25

  • 0.4 -0.2

0.2 0.4

  • 0.4
  • 0.2

0.2 0.4 5 10 15 20 25

r⊥ Λmed r⊥ Λmed

Rmed Rmed

JCS, Mehtar-Tani, Tywoniuk, Salgado arXiv:1210.7765

Rmed 2 ✓Z d⌅ ⌅2ˆ q(⌅) ◆−1/2

ξ ≡ path length

➤ Effective emitters control energy loss fluctuations

31

๏ Jet substructure is resolved by the medium

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SLIDE 32

Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Finite Resolution at Strong Coupling

xêzH yêzH z zH

  • 20
  • 10

10 20

  • 5

5

  • 1.0
  • 0.5

0.0

JCS, Ficnar 1512.00371

32

5 10 15 20

  • 6
  • 4
  • 2

2 4 6

x ê zH y ê zH

5 10 15 20

  • 6
  • 4
  • 2

2 4 6

x ê zH y ê zH

resolved jets un-resolved jets

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Single Particle Spectra

33

0.2 0.4 0.6 0.8 1 1.2 1 10 100 1000 Lres = 2/πT w/ nPDF LO EPS09

  • Ch. Hadron RAA

Hadron PT (GeV) Strong Coupling 0-10% Strong Coupling 10-30% Strong Coupling 10-30% CMS 0-10 % CMS 10-30 % CMS 30-50 %

√s = 5.02 ATeV

imp ag

JCS, Gulhan, Hylcher, Milhano, Pablos, Rajagopal in preparation

๏ Resolution effects are important for single particle suppression

0.2 0.4 0.6 0.8 1 1.2 1 10 100 1000 No Res w/ nPDF LO EPS09

  • Ch. Hadron RAA

Hadron PT (GeV) Strong Coupling 0-10% Strong Coupling 10-30% Strong Coupling 10-30% CMS 0-10 % CMS 10-30 % CMS 30-50 %

te ce

√s = 5.02 ATeV

0.2 0.4 0.6 0.8 1 10 Nuc PDF 0 − 5% AuAu √s = 200 AGeV π0 RAA Hadron PT (GeV) Lres = 2/πT No Res PHENIX Data under scrutiny

Preliminary

๏ But also to reconcile the √s dependence of quenching

➤ A common problem in all models of jet quenching

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Conclusions

34

๏ Heavy ion collisions provide access to the QGP

➤ Deconfined matter ➤ A very good fluid ➤ A system with no quasiparticles

๏ Hard probes provide access to the microscopic dynamics

➤ Promising description based on strong coupling techniques ➤ Dynamical implementation: allows us to understand successes and limitations ➤ Ultimate goal: can we understand the nature of plasma degrees of freedom from these measurements?

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

35

Back up

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Insensitivity

36

0.5 1 1.5 2 30 40 50 60 70 80 90 100 IAA Jet PT 0 − 30% Centrality P jet T > 30 GeV ∆φ > 7π/8 60 < P γ T < 80 GeV Strong Coupling Radiative Collisonal Data 0.2 0.4 0.6 0.8 1 1.2 1.4 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 1 Nγ dNJγ dxJγ xJγ 0 − 10% Centrality pjet T > 30 GeV ∆φ > 7π/8 Strong Coupling Radiative Collisonal Smeared pp Data 0.2 0.4 0.6 0.8 1 40 50 60 70 80 90 100 110 RJγ P γ T 0 − 30% Centrality P jet T > 30 GeV ∆φ > 7π/8 Strong Coupling Radiative Collisonal Smeared pp Data 0.05 0.1 0.15 0.2 0.25 0.3 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Event Fraction AJ 0 − 10% Centrality Vacuum+Smearing Data Strong Coupling Radiative Collisonal 0.2 0.4 0.6 0.8 1 1.2 100 120 140 160 180 200 220 240 260 280 300 Jet RAA PT (GeV) 0-10% Centrality Strong Coupling Radiative Data Collisional −0.5 0.5 1 1.5 2 2.5 3 0.5 1 1.5 2 2.5 3 0 − 30% P Z0 T > 60 GeV, P jet T > 30 GeV |ηjet| < 1.6, |ηZ0| < 2.5 1 NZ0 dNJZ0 d∆φJZ ∆φ Strong Coupling Radiative Collisional Smeared pp PbPb CMS 0.2 0.4 0.6 0.8 1 1.2 1.4 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 0 − 30% Centrality P jet T > 30 GeV ∆φ > 7π/8 1 NZ0 dNJZ0 dxJZ0 xJZ0 Strong Coupling Radiative Collisonal Smeared pp PbPb CMS
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Birmingham Particle Physics Group

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07th June 2017

3-Jet events

  • ➤ Soft fields between colour objects

Lund string model: gluons associated to kinks in the string

37

๏ Hard gluon emission by an energetic q-q pair

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Birmingham Particle Physics Group

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07th June 2017

Strong vs Weak

38

θres = 24/3 π Γ(3/4)2 Γ(5/4)2 ✓ E p λT ◆2/3

๏ Resolution angle infinite medium

Finite length medium

๏ At weak coupling: ๏ Infinite medium, maximal length= stopping distance

jet, ∆x [42], the as θpQCD

res

/ E3/4 erstand whether th

๏ Fluctuations in jet energy loss may help distinguish between the

different microscopic realisations

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Birmingham Particle Physics Group

  • J. Casalderrey-Solana

07th June 2017

Jets in Vacuum

39

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Birmingham Particle Physics Group

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07th June 2017

Jets in Pb-Pb

40

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Birmingham Particle Physics Group

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07th June 2017

Recovering Jet Energy

41

➤ Comment on crude

hadronic treatment

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Birmingham Particle Physics Group

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07th June 2017

42

40 30 20 10 10 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 PbPb R=0.3, 0-30% Quenching + Medium Response h/ pk

T i

∆ 8.0-300.0 4.0-8.0 2.0-4.0 1.0-2.0 0.5-1.0 h/ pk

T i∆

CMS