The quark gluon plasma
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The Quark-Gluon Plasma. Marco van Leeuwen. Elementary particles. Standard Model: elementary particles. Quarks: Electrical charge Strong charge (color). up charm top down strange bottom. +anti-particles. Leptons: Electrical charge. electron Muon Tau n e n m n t.

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The Quark-Gluon Plasma

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The quark gluon plasma

The Quark-Gluon Plasma

Marco van Leeuwen


Elementary particles

Elementary particles

Standard Model: elementary particles

Quarks:

Electrical charge

Strong charge (color)

up charm top

down strange bottom

+anti-particles

Leptons:

Electrical charge

electron Muon Tau

nenmnt

photon EM force

gluon strong force

W,Z-boson weak force

Force carriers:

Atom

Electronelementary, point-particle

Protons, neutrons

Composite particle

 quarks

EM force binds electronsto nucleus in atom

Strong force binds nucleonsin nucleus and quarks in nucleons


Qcd and hadrons

QCD and hadrons

Quarks and gluons are the fundamental particles of QCD

(feature in the Lagrangian)

However, in nature, we observe hadrons:

Color-neutral combinations of quarks, anti-quarks

Baryon multiplet

Meson multiplet

S

strangeness

I3 (u,d content)

I3 (u,d content)

Mesons: quark-anti-quark

Baryons: 3 quarks


Seeing quarks and gluons

Seeing quarks and gluons

In high-energy collisions, observe traces of quarks, gluons (‘jets’)


How does it fit together

How does it fit together?

S. Bethke, J Phys G 26, R27

Running coupling:

as decreases with Q2

Pole at m = L

LQCD ~ 200 MeV ~ 1 fm-1

Hadronic scale


Asymptotic freedom and pqcd

Asymptotic freedom and pQCD

At high energies, quarks and gluons are manifest

At large Q2, hard processes: calculate ‘free parton scattering’

+ more subprocesses


Low q 2 confinement

Low Q2: confinement

a large, perturbative techniques not suitable

Bali, hep-lat/9311009

Lattice QCD: solve equations of motion (of the fields) on a space-time lattice by MC

Lattice QCD potential

String breaks, generate qq pair to reduce field energy


Qcd matter

QCD matter

Energy density from Lattice QCD

g: deg of freedom

Nuclear matter

Quark Gluon Plasma

Bernard et al. hep-lat/0610017

Tc ~ 170 -190 MeV

ec ~ 1 GeV/fm3

Deconfinement transition: sharp rise of energy density at Tc

Increase in degrees of freedom: hadrons (3 pions) -> quarks+gluons (37)


Qcd phase diagram

QCD phase diagram

Quark Gluon Plasma

(Quasi-)free quarks and gluons

Temperature

Critical

Point

Early universe

Confined hadronic matter

High-density phases?

Elementary collisions

(accelerator physics)

Neutron stars

Nuclear matter

Bulk QCD matter: T and mB drive phases


Heavy ion collisions

Heavy ion collisions

Lac Leman

Lake Geneva

Geneva airport

CERN

Meyrin site

Collide large nuclei at high energy to generate high energy density

 Quark Gluon PlasmaStudy properties

RHIC: Au+Au sNN = 200 GeV

LHC: Pb+Pb √sNN≤ 5.5 TeV

27 km circumference


Nuclear geometry n part n bin l e

Nuclear geometry: Npart, Nbin, L, e

b

y

L

Npart: nA + nB (ex: 4 + 5 = 9 + …)

Nbin: nA x nB (ex: 4 x 5 = 20 + …)

  • Two limits:

  • - Complete shadowing, each nucleon only interacts once, s Npart

  • No shadowing, each nucleon interact with all nucleons it encounters, s  Nbin

  • Soft processes: long timescale, large s,stot Npart

  • Hard processes: short timescale, small s, stot Nbin

Transverse view

Density profile r: rpart or rcoll

Eccentricity

x

Path length L, mean <L>


Centrality examples

Centrality examples

... and this is what you see in a presentation

central

peripheral

mid-central

This is what you really measure


Centrality dependence of hard processes

Centrality dependence of hard processes

Total multiplicity: soft processes

Binary collisions weight

towards small impact parameter

ds/dNch

200 GeV Au+Au

  • Rule of thumb for A+A collisions (A>40)

    • 40% of the hard cross section is contained in the 10% most central collisions


Selected topics in heavy ions

Selected topics in Heavy Ions

  • Elliptic flow

    • Bulk physics, low pT, expansion driven by pressure gradients

  • Parton energy loss

    • High-energy parton ‘probes’ the quark gluon plasma

    • Light/heavy flavour


Collective motion

Collective Motion

Only type of collective transverse motion in central collision (b=0) is radial flow.

Integrates pressure history over complete expansion phase

Elliptic flow, caused by anisotropic initial overlap region (b > 0)

More weight towards early stage of expansion (the QGP phase)


Forming a system and thermalizing

Forming a system and thermalizing

Animation: Mike Lisa

1) Superposition of independent p+p:

momenta pointed at random

relative to reaction plane

b


Forming a system and thermalizing1

Forming a system and thermalizing

Animation: Mike Lisa

1) Superposition of independent p+p:

high

density / pressure

at center

momenta pointed at random

relative to reaction plane

2) Evolution as a bulksystem

Pressure gradients (larger in-plane) push bulk “out” “flow”

“zero” pressure

in surrounding vacuum

more, faster particles seen in-plane

b


How does the system evolve

How does the system evolve?

N

N

0

0

/4

/4

/2

/2

3/4

3/4

-RP (rad)

-RP (rad)

1) Superposition of independent p+p:

momenta pointed at random

relative to reaction plane

2) Evolution as a bulksystem

Pressure gradients (larger in-plane) push bulk “out” “flow”

more, faster particles seen in-plane

Animation: Mike Lisa


Energy dependence of flow

Energy dependence of flow

  • Flow at RHIC consistent with ideal hydrodynamics!! … so what will we get at LHC ?

NA49, PRC68, 034903


Hard probes of qcd matter

Hard probes of QCD matter

Use ‘quasi-free’ partons from hard scatterings

Calculable with pQCD

to probe ‘quasi-thermal’ QCD matter

Quasi-thermal matter: dominated by soft (few 100 MeV) partons

Interactions between parton and medium:

  • Radiative energy loss

  • Collisional energy loss

  • Hadronisation: fragmentation and coalescence

Sensitive to medium density, transport properties


Energy loss in qcd matter

Energy loss in QCD matter

radiated gluon

propagating parton

m2

QCD bremsstrahlung(+ LPM coherence effects)

Transport coefficient

l

Energy loss

Energy loss probes:

Density of scattering centers:

Nature of scattering centers, e.g. mass: radiative vs elastic loss

Or no scattering centers, but fields  synchrotron radiation?


P 0 r aa high p t suppression

p0 RAA – high-pT suppression

: no interactions

RAA = 1

Hadrons: energy loss

RAA < 1

: RAA = 1

0: RAA≈ 0.2

Hard partons lose energy in the hot matter


Two extreme scenarios

Two extreme scenarios

Scenario I

P(DE) = d(DE0)

Scenario II

P(DE) = a d(0) + b d(E)

1/Nbin d2N/d2pT

‘Energy loss’

‘Absorption’

p+p

Downward shift

Au+Au

Shifts spectrum to left

pT

P(DE) encodes the full energy loss process

Need multiple measurements to distentangle processes

RAA gives limited information


R aa at lhc

RAA at LHC

GLV

BDMPS

T. Renk, QM2006

RHIC

RHIC

S. Wicks, W. Horowitz, QM2006

LHC: typical parton energy > typical E

Expected rise of RAA with pT depends on energy loss formalism

Nuclear modification factor RAA at LHC sensitive to radiation spectrum P(E)


Summary

Summary

  • Elementary particles of the strong interaction (QCD): quarks and gluon

  • Bound states: p, n, p, K (hadrons)

  • Bulk matter: Quark-Gluon-Plasma

    • High T~200 MeV

  • Heavy ion collisions:

    • Produce and study QGP

    • Elliptic flow

    • Parton energy loss


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