john harris (yale) 16 th conference of czech & slovak physicists, hradec králové, 10 sept....

John Harris (Yale) 16th Conference of Czech & Slovak Physicists, Hradec Králové, 10 Sept. 2008

Exploring the Quark-Gluon Plasma at RHIC & LHC –Today’s Perspective

On the “First Day”

There was light!gravity electro-electro-

magnetismmagnetism

weakstrong

at 10-43 seconds

then at 10 -seconds

& 2 x 1012 Kelvin

Quark-to-hadron

phase transition

Rapid inflation

gravity, strong & E-W

forces separate

Quark-Gluon Plasma


Behavior of QCD at High Temperature

few d.o.f.confined

many d.o.f.deconfined

F. Karsch, et al.Nucl. Phys. B605 (2001) 579

TC ~ 175 8 MeV C ~ 0.3 - 1 GeV/fm3

/T4 ~ # degrees of freedom

24

30T


Modifications to QCD Coupling Constant s

heavy quark-antiquark coupling at finite T from lattice QCD O.Kaczmarek, hep-lat/0503017

Constituents - Hadrons, dressed quarks, quasi-hadrons, resonances?

Coupling strength variesinvestigates (de-)confinement, hadronization, & intermediate objects.

low Q2high Q2

D. Gross

H.D. Politzer

F. Wilczek

QCD Asymptotic Freedom (1973)

Nobel Prize 2005

“Before [QCD] we could not go back further than 200,000 years after the Big Bang. Today…since QCD simplifies at high energy, we can extrapolate to very early times when nucleons melted…to form a quark-gluon plasma.” David Gross, Nobel Lecture (RMP 05)


Phase Diagram of QCD MatterT

emp

erat

ure

baryon density

Early universe

nucleinucleon gas

hadron gascolor

superconductor

quark-gluon plasma

Tc

~ 1

70

Me

V

0

Critical point ?

vacuum

CFLNeutron stars

see: Alford, Rajagopal, Reddy, Wilczek Phys. Rev. D64 (2001) 074017L

HC

RHIC


John Harris (Yale) U. Texas – Austin, Colloquium, 14 Nov. 2007

Quark-Gluon Plasma• Standard Model Lattice Gauge Calculations predict

QCD Deconfinement phase transition at T = 175 MeV

• Cosmology Quark-hadron phase transition in early Universe

• Astrophysics Cores of dense stars (?)

• Establish properties of QCD at high T (and density?)

• Can we make it in the lab?

Quark-Gluon Plasma (Soup)


Ultra-Relativistic Heavy Ion Collisions

General Orientation

Hadron (baryons, mesons) masses ~ 1 GeV

Hadron sizes ~ 10-15 meters (1 fm ≡ 1 fermi)

RHIC Collisions

Ecm = 200 GeV/nn-pair

Total Ecm = 40 TeV

Gold nucleusdiameter = 14 fm

= 100 (Lorenz contracted)

= (14 fm/c) / ~ 0.1 fm/c

Interaction of Au nuclei complete in few tenths fm/c


John Harris (Yale) Hadron 07 - Frascati, Italy, 8 -13 Oct. 2007

Ultra-Relativistic Heavy Ion Collision at RHIC

PHOBOS

Au + Au

On the “First Day” (at RHIC)

Large energy densities dn/ddET/d

GeV/fm3 critical

x nuclear density

Large collective flow

ed. - “completely unexpected!”

Due to large early pressure gradients, energy & gluon densities

Requires hydrodynamics and quark-gluon equation of state

Quark flow & coalescence constituent quark degrees of freedom!

1

PHENIX

Initial Observations:Large produced particle multiplicities

ed. - “less than expected! gluon-saturation?”

dnch/d |=0 = 670, Ntotal ~ 7500

15,000 q +q in final state, > 92% are produced quarks

CGC?


How do RHIC Collisions Evolve?

b

1) Superposition of independent p+p:

momenta randomrelative to reaction plane

Reaction plane


How do RHIC Collisions Evolve?

b


2) Evolution as a bulk system


High densitypressureat center

“zero” pressurein surrounding vacuum

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

more, faster particles seen in-plane


Mike Lisa

in practice with Uli and Mercedes, took 1/2 hour to get to this slide


2) Evolution as a bulk system

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

more, faster particles seen in-plane

N

-RP (rad)0 /2 /4 3/4

N

-RP (rad)0 /2 /4 3/4


Azimuthal Angular Distributions


On the First Day at RHIC - Azimuthal DistributionsSTAR, PRL90 032301 (2003)

b ≈ 4 fm

“central” collisions

b ≈ 6.5 fm

midcentral collisions

Top view

Beams-eye view

1


STAR, PRL90 032301 (2003)

b ≈ 4 fmb ≈ 6.5 fmb ≈ 10 fm

peripheral collisions

Top view

Beams-eye view

On the First Day at RHIC - Azimuthal Distributions1


Elliptic Flow Saturates Hydrodynamic Limit

• Azimuthal asymmetry of charged particles: dn/d ~ 1 + 2 v2(pT) cos (2) + ...x

z

y

curves = hydrodynamic flowzero viscosity, Tc = 165 MeV

1

Mass dependence of v2

Requires -

• Early thermalization (0.6 fm/c)

• Ideal hydrodynamics

(zero viscosity)

“nearly perfect fluid”

• ~ 25 GeV/fm3 ( >> critical )

• Quark-Gluon Equ. of StateJohn Harris (Yale) 16th Conference of Czech & Slovak Physicists, Hradec Králové, 10 Sept. 2008

Identified Hadron Elliptic Flow ComplicatedComplicated v2(pT) flow pattern is observed for identified hadrons

d2n/dpTd ~ 1 + 2 v2(pT) cos (2 )

Baryons

Mesons

If the flow established at quark level, it is predicted to be simple KET KET / nq , v2 v2 / nq , nq = (2, 3 quarks) for (meson, baryon)

15000 quarksflow collectively


If baryons and mesons form

from independently flowing quarks

then

quarks are deconfined

for a brief moment (~ 10 -23 s), then hadronization!


Transport in gases of strongly-coupled atoms

RHIC fluid behaves like this –

a strongly coupled fluid.

Universality of Classical Strongly-Coupled Systems?

Universality of classical strongly-coupled systems? Atoms, sQGP, ……. AdS/CFT…… K.M. O’Hara et al

Science 298 (2002) 2179

Use strongly coupled N = 4 SUSY YM theory.

Derive a quantum lower viscosity bound: s > 1/4

AdS5/CFT – a 5D Correspondence of 4D Systems

• Analogy between black hole physics and equilibrium thermodynamics

• Solutions possess hydrodynamic characteristicsSimilar to fluids – viscosity, diffusion constants,….

our world - 3 + 1 dim brane

horizon

Extra dim

ension

(the bulk)

MULTIPLICITY

Entropy Black Hole Surface Area

DISSIPATION

Viscosity Graviton Absorption


Ultra-low (Shear)Viscosity Fluids

4 s

Quantum lower viscosity bound: s > 1/4 (Kovtun, Son, Starinets)

From strongly coupled N = 4 SUSY YM theory.

2-d Rel Hydro describes STAR v2 data with /s 0.1 near lower bound!

s (limit) = 1/4

s (water) >10

QGP

T = 2 x 1012 K


“The RHIC fluid may be the

least viscous fluid ever seen”

The American Institute of Physics

announced the RHIC quark-gluon liquid

as the top physics story of 2005!see http://www.aip.org/pnu/2005/


It Flows - Is It Really Thermalized?

“Chemical” equilibration (particle yields & ratios):

Particles yields represent equilibrium abundances

universal hadronization temperature

Small net baryon density K+/K-,B/B ratios) B ~ 25 - 40 MeV

Chemical Freezeout Conditions T = 177 MeV, B = 29 MeV T ~ Tcritical (QCD)


Particles are thermally distributed and flow collectively,

at universal hadronization temperature T = 177 MeV!


On the “Second” Day (~ Year) at RHIC

Probing Hot QCD Matter with Hard-Scattered Probes

hadrons

leading particle

hadrons

leading particle

parton energy loss: modification of jets and leading particles & jet-correlations


High Momentum Hadrons Suppressed - Photons Not

Photons

Hadrons factor 4 – 5 suppression

dev/

AAAA /

coll pp

NR

N N

Deviations from binary scaling of hard collisions:


Dynamical Origin of High pT Hadron Suppression?

What happens to the radiation?

For collisional energy losswhat about recoil energy?

Egluon > Equark, m=0 > Equark, m>0

What is the dependenceon the type of parton?

E

How does parton lose energy?

q = 2 / ^One parameterization of energy loss

q ~


Parameterization of Parton Energy Loss

q ~

Eskola, Honkanen, Salgado, WiedemannNucl Phys A747 (2005) 511

q ^

q = 5 – 15 GeV2 / fm from RHIC RAA Data ^


Interpretation of the Parton Energy Loss

q ~

RHIC data

R. Baier, Nucl Phys A715, 209c

QGP

Pion gas

Cold nuclear matter

sQGP

Energy loss requires large(also : Dainese, Loizides, Paic, hep-ph/0406201)

2ˆ 5 10 GeV /fmq 5 - 15


Heavy Quark Suppression• Using fixed order next-to-

leading log (FONL) cross

sections for charm and

beauty

Armesto, Cacciari, Dainese, Salgado, Wiedemann,PLB637:362, 2006

Insufficient suppression from theoretical models!


AdS5/CFT Again! - Initial Results on Jet Quenching

H. Liu, K. Rajagopal and U. A. Wiedemann, arXiv:hep-ph/0605178, recent PRL

from J. J. Friess, S. S. Gubser and

G. Michalogiorgakis,arXiv:hep-th/0605292.


Hard Scattering (Jets) as a Probe of Dense Matter II

Jet event in eecollision STAR p + p jet event

Can we see jets in high energy Au+Au?

STAR Au+Au (jet?) event


Where Does the Energy Go? dev

Jet correlations in proton-proton reactions.

Strong back-to-back peaks.

Jet correlations in central Gold-Gold.

Away side jet disappears for particles pT > 2 GeV

Jet correlations in central Gold-Gold.

Away side jet reappears in particles pT > 200 MeV

Azimuthal Angular CorrelationsLost energy of away-side jet is redistributed to rather large angles!

Color wakes?

J. Ruppert & B. Müller

Mach cone from sonic boom?

H. Stoecker

J. Casalderrey-Solana & E. Shuryak

Cherenkov-like gluon radiation?

I. Dremin

A. Majumder, X.-N. Wang

Medium-induced gluon radiation?

Polosa, C. Salgado


The suppression of high pT hadrons and the quenching of jets

indicates the presence of a high density, strongly-coupled

colored medium. !


The Quark-Gluon Plasma – Present View from RHIC

RHIC and new Large Hadron Collider (LHC) at CERN in Geneva:

Will cover 2 – 3 decades of energy (sNN ~ 20 GeV – 5.5 TeV)

To uncover the properties of hot QCD at T ~ 150 – 600 MeV)

• Large > c (T > Tc) system – Sufficient for QGP formation – NOT hadrons

• Large volume of quarks & gluons (hydrodynamics) – NOT just q & g scattering

Large elliptic & radial flow large pressure gradients

Ultra-low shear viscosity “nearly-perfect” fluid flow

Particle ratios fit by thermal model T = 177 MeV ~ Tc (lattice QCD)

• Dynamics of quarks and gluons – NOT hadrons

Flow depends upon constituent quark masses

Flow develops at quark level QGP EoS, quark coalescence

• NOT a Weakly-interacting QGP (as we initially expected from Lattice QCD)

Strongly interacting quarks and gluons NOT s ~ 0



Officially Starts Today!

Geneva with Large Hadron Collider Superimposed


The Future of RHI‘s at the LHC:

Dedicated HI experiment - ALICE

Two pp experiments with HI program:

ATLAS and CMS

Simple Extrapolation to Heavy Ion Physics at LHC

QGP (fm/c)

(GeV/fm3)

T / Tc

tform (fm/c)

√sNN (GeV) factor 28

2-4

5

1.9

0.2

200

RHIC

≤ 2

3

1.1

1

17

LHCSPS

5500

0.1 shorter

3.0 - 4.2 hotter

15-60 denser

> 10longer-lived


Heavy Ion Physics at the LHC – ExpectationsLHC Heavy Ions –

• expectations based on pQCD predictions & RHIC results• a lesson from RHIC – guided by theory + versatility + “expect the unexpected”

Soft Physics (pT ≤ 2 GeV/c) at LHC – • smooth extrapolation from SPS RHIC LHC?• expansion dynamics different? (flow, HBT, Tchem & Tkin, strange/charm/beauty)

Elliptic FlowParticle Multiplicities

Ntot ~ 6000

Ntot ~ 2000



Significant increase in hard cross sections

(pT or mass > 2 GeV/c) at LHC – large pT /total~ 2% at SPS

50% at RHIC

98% at LHC• “real” jets, large pT processes

• abundance of heavy flavors• probe early times, calculable

bb (LHC ) ~ 100 bb (RHIC)

cc (LHC) ~ 10 cc (RHIC)

Rat

e

Hard Probes with LHC Heavy Ions

LHC Heavy Ion Programs

Heavy Ion Data-taking

Pb + Pb at sNN = 5.5 TeV


The ALICE Heavy Ion Experiment


ALICE Collaboration

~ 1000 Members ~ 30 Countries ~ 100 Institutes


• Czech Republic:

Praha, Academy of Sciences of the Czech Republic, Institute of Physics

Praha, Czech Technical University of Prague CTU

Rez, Academy of Sciences of the Czech Republic, Nuclear Physics Institute

• Slovakia:

Bratislava, Comenius University, Faculty of Mathematics, Physics and Informatics

Kosice, Institute of Experimental Physics, Slovak Academy of Sciences

The ALICE Experiment Installation


RAA d 2N AA dydpT

d 2N pp dydpT NcollAA

Is the QCD phase diagram feature-less at 1 – 4 Tc?

What happens as we go up in T (e.g. coupling)?

Are there new phenomena?

What’s the range of theoretical validities (non-pQCD, pQCD, strings)?

Measure/understand parton energy loss at the fundamental level

Establish flavor (gluon and quark mass) dependence

Use jets and/or photons to establish hard-scattered parton energy

Jet modifications - longitudinal & transverse “heating”

Medium response to jet-heating (near- and away-side)

Measure/use open charm and beauty decays (also as jet-tags)

cc and bb states (Ti, screening/suppression, enhancement?)

Direct Photon Radiation?

Developments in theory (lattice, hydro, parton E-loss, string theory…)

“the next frontier!”

The Quark-Gluon Plasma at LHC – Questions


The New Yorker, Jan. 7 2007

….and the String Theory discussion/debate continues…


Special Thanks for Contributions to This Presentation!!

Miklos Gyulassy

Peter Jacobs

Mike Lisa

Thomas Ullrich

Urs Wiedemann


The End

john harris (yale) 16 th conference of czech & slovak physicists, hradec králové, 10 sept....

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