The Quark Gluon PlasmaThe Quark Gluon Plasmawhat is it and why should it exist ?what is it and why should it exist ?

The first second of the universeThe first second of the universe

from D.J. Schwarz, astro-ph/0303574from D.J. Schwarz, astro-ph/0303574

AP NP HEP

time

History of the early universeHistory of the early universe

The tools need to study the early history of the universe:

- Accelerator based high energy and nuclear experiments (LHC, RHIC)- Observational cosmology (LSST, HAWC, etc.)

Going back in time…Going back in time…

AgeAge Energy Energy Matter in universe Matter in universe 00 10101919 GeV GeV grand unified theory of all forcesgrand unified theory of all forces

1010-35-35 s s 10101414 GeV GeV 11stst phase transition phase transition (strong: q,g + electroweak: g, l,n)(strong: q,g + electroweak: g, l,n)

1010-10-10 ss 101022 GeV GeV 22ndnd phase transition phase transition

(strong: q,g + electro: g + weak: l,n)(strong: q,g + electro: g + weak: l,n)

1010-5-5 s s 0.2 GeV0.2 GeV 33rdrd phase transition phase transition

(strong:hadrons + electro:g + weak: l,n)(strong:hadrons + electro:g + weak: l,n)

3 min.3 min. 0.1 MeV0.1 MeV nucleinuclei

6*106*1055 years years 0.3 eV0.3 eV atomsatoms

Now Now 3*103*10-4-4 eV = 3 K eV = 3 K (13.7 billion years)(13.7 billion years)

RHIC, LHC & FAIR

FRIB & FAIR

Strong color fieldForce grows with separation !!!

Analogies and differences between QED and QCDAnalogies and differences between QED and QCD

to study structure of an atom…

“white” proton

…separate constituents

Imagine our understanding of atoms or QED if we could not isolate charged objects!!

nucleus

electron

quark

quark-antiquark paircreated from vacuum

“white” proton(confined quarks)

“white” 0

(confined quarks)

Confinement: fundamental & crucial (but not understood!) feature of strong force- colored objects (quarks) have energy in normal vacuum

neutral atom

To understand the strong force and the phenomenon of confinement:Create and study a system of deconfined colored quarks (and gluons)

F ~ 1/r2

F ~ r

The main features of Quantum Chromodynamics The main features of Quantum Chromodynamics (QCD) (QCD)

(Nobel Prize 2004)(Nobel Prize 2004)

ConfinementConfinement• At large distances the effective coupling between quarks is At large distances the effective coupling between quarks is

large, resulting in confinement.large, resulting in confinement.• Free quarks are not observed in nature.Free quarks are not observed in nature.

Asymptotic freedomAsymptotic freedom• At short distances the effective coupling between quarks At short distances the effective coupling between quarks

decreases logarithmically.decreases logarithmically.• Under such conditions quarks and gluons appear to be quasi-Under such conditions quarks and gluons appear to be quasi-

free.free. (Hidden) chiral symmetry(Hidden) chiral symmetry

• Connected with the quark massesConnected with the quark masses• When confined quarks have a large dynamical mass - When confined quarks have a large dynamical mass -

constituent massconstituent mass• In the small coupling limit (some) quarks have small mass - In the small coupling limit (some) quarks have small mass -

current masscurrent mass

Theoretical and computational QCDTheoretical and computational QCDin vacuum and in mediumin vacuum and in medium

In vacuum: - asymptotically free quarks have current mass- confined quarks have constituent mass- baryonic mass is sum of valence quark constituent masses

Masses can be computed as a function of the evolving coupling strength or the ‘level of asymptotic freedom’, i.e. dynamic masses.

But the universe was not a vacuum at the time of hadronization, it was likely a plasma of quarks and gluons. Is the mass generation mechanism the same ?

B.Mueller (2004):New Discoveries at RHIC

The evolution of luminous matterThe evolution of luminous matter

Electro-weak symmetry breaking via Higgs field (m of W, Z, Mechanism to generate current quark masses (but does not explain their magnitude)

Standard model is symmetric. All degrees of freedom are massless.

QCD phase transition (I):chiral symmetry breaking via dynamical quarks. Mechanism to generate constituent quark masses (but does not explain hadronization)

QCD phase transition (II):Confinement to hadrons. Mechanism to generate hadron properties (but does not explain hadron masses)

What can we do in the laboratory ?What can we do in the laboratory ?a.) Re-create the conditions as close as possible to the a.) Re-create the conditions as close as possible to the Big Bang, i.e. a condition of maximum density and Big Bang, i.e. a condition of maximum density and minimum volume in an expanding macroscopic system. minimum volume in an expanding macroscopic system. Is statistical thermodynamics applicable ?Is statistical thermodynamics applicable ?

b.) b.) Measure a phase transitionMeasure a phase transition, characterize the new , characterize the new phase, measure the de-excitation of the new phase into phase, measure the de-excitation of the new phase into ‘ordinary’ matter – ‘ordinary’ matter – ‘do we come out the way went in ?’‘do we come out the way went in ?’(degrees of freedom, stable or metastable matter, (degrees of freedom, stable or metastable matter, homogeneity)homogeneity)

c.) Learn about hadronization (how do particles acquire c.) Learn about hadronization (how do particles acquire mass) – complementary to the Higgs search but with mass) – complementary to the Higgs search but with the same goal. the same goal. The relevant theory is Quantum Chromo The relevant theory is Quantum Chromo DynamicsDynamics

Generating a deconfined stateGenerating a deconfined state

Nuclear Matter(confined)

Hadronic Matter(confined)

Quark Gluon Plasmadeconfined !

Present understanding of Quantum Chromodynamics (QCD)• heating• compression deconfined color matter !

Expectations from Lattice QCDExpectations from Lattice QCD/T4 ~ # degrees of freedom

confined:few d.o.f.

deconfined:many d.o.f.

TC ≈ 173 MeV ≈ 21012 K ≈ 130,000T[Sun’s core]C 0.7 GeV/fm3

The phase diagram of QCDThe phase diagram of QCDT

em

per

atu

re

baryon density

Neutron stars

Early universe

nucleinucleon gas

hadron gascolour

superconductor

quark-gluon plasmaTc

0

critical point ?

vacuum

CFL

RHIC BRAHMSPHOBOS

PHENIXSTAR

AGS

TANDEMS

RRelativistic elativistic HHeavy eavy IIon on CCollider (RHIC)ollider (RHIC)

1 mile

v = 0.99995c

Au+Au @ sNN=200 GeV

Study all phases of a heavy ion collisionStudy all phases of a heavy ion collision

If the QGP was formed, it will only live for 10-21 s !!!!BUT does matter come out of this phase the same way it went in ???

Study all phases of a heavy ion collisionStudy all phases of a heavy ion collision

If the QGP was formed, it will only live for 10-21 s !!!!BUT does matter come out of this phase the same way it went in ???

Proving the existence of a new phase of matterProving the existence of a new phase of matter

Can we prove that we have a phase thatCan we prove that we have a phase thatbehaves different than elementary pp collisions ?behaves different than elementary pp collisions ?

Three steps:Three steps:

a.) prove that the phase is partonica.) prove that the phase is partonic

b.) prove that the phase is collectiveb.) prove that the phase is collective

c.) prove that the phase characteristics (state variables) c.) prove that the phase characteristics (state variables) are different from the QCD vacuumare different from the QCD vacuum

Proof (a) for partonic medium creationProof (a) for partonic medium creationShooting a high momentum particle through a Shooting a high momentum particle through a

dense mediumdense medium

p

p

?

Au+Au

idea: p+p collisions @ same sNN = 200 GeV as reference

?: what happens in Au+Au to jets which pass through medium?

Prediction: scattered quarks radiate energy (~ GeV/fm) in the colored medium: “quenches” high pT particles “kills” jet partner on other side

STAR, nucl-ex/0305015

energyloss

pQCD + Shadowing + Cronin

pQCD + Shadowing + Cronin + Energy Loss

RRAAAA and high-pT suppression and high-pT suppression

Deduced initial gluon density at = 0.2 fm/c dNglue/dy ≈ 800-1200

≈ 15 GeV/fm3, eloss = 15*cold nuclear matter (compared to HERMES eA) (e.g. X.N. Wang nucl-th/0307036)

SYSTEM NEEDS TO BE PARTONIC

Proof (b): is the matter behaving collective ? Proof (b): is the matter behaving collective ? elliptic (anisotropic)elliptic (anisotropic) flowflow

Dashed lines: hard sphere radii of nuclei

Reactionplane

In-planeOu

t-o

f-p

lan

e

Y

XFlow

Flo

w

Y

XTime

Directed flow Elliptic flow

Mid-centralcollision

Proof (c): new phase leads to new matter production mechanismProof (c): new phase leads to new matter production mechanism The medium consists of constituent quarks ?The medium consists of constituent quarks ?

Massive quasiparticles instead of current quarks ?Massive quasiparticles instead of current quarks ?

baryonsbaryons

mesonsmesons

Elliptic flow exists and its magnitude is Elliptic flow exists and its magnitude is described by ideal hydrodynamics !described by ideal hydrodynamics !

Hydrodynamics:strong coupling,small mean free path:many interactionsNOT plasma-likesystem behaves liquid-like

Strong collective flow:elliptic expansion withmass ordering

x

yz

A surprise: ideal liquid behaviorA surprise: ideal liquid behavior

First time in heavy-ion collisions we created a system which is in quantitative agreement with ideal hydrodynamic model. The new phase behaves like an ideal liquid rather than a plasma.

Not anticipated. In stark contrast to pQCD.

How strong is the coupling ?How strong is the coupling ?Simple pQCD processes do not generate sufficient interaction strength. Navier-Stokes type calculation of viscosity yield a near perfect liquidViscous force ~ 0. We have made a sQGP not the anticipated wQGP.

?

Experimental verification at RHICExperimental verification at RHIC

Lacey et al., PRL 98 (2007) 092301

The quantum limit has been reached at RHIC and hasbeen independently verified in several measurements of collective effects

RB, J.Phys.G35:044504 (2008)

Hirano, Gyulassy (2006)

Lessons from Lessons from RHIC: RHIC:

The Quark The Quark SoupSoup

AIP ScienceAIP ScienceStory of 2006Story of 2006

The future is brightThe future is brightA three prong approach:

lower energy better facility higher energy

FAIR: Facility for Antiproton & Ion Reseach

                                                    

LHC: Large Hadron Colliderwith ALICE, CMS, ATLAS

RHIC-II:RHIC upgradewith higher luminosity andupgraded detectors

Measuring pp/AA in all LHC experimentsMeasuring pp/AA in all LHC experiments

ALICEALICE Dedicated & most versatile heavy ion Dedicated & most versatile heavy ion

detectordetector Important for particle identified Important for particle identified

fragmentation measurements in ppfragmentation measurements in pp

CMS/ATLASCMS/ATLAS

Dedicated & most versatile p+p Dedicated & most versatile p+p detectorsdetectors

Important for calorimeter based jet Important for calorimeter based jet measurements in A+Ameasurements in A+A..