Weegluonsandtheirbigroleincrea2ngtheho3estma3eronearth

RajuVenugopalan

BNL

INT@20Symposium,Sea3le,July1‐2,2010

QuantumChromodynamics(QCD)

•  Theoryisrichinsymmetries:

iii iii

i)  Gauge“color”symmetry:unbrokenbutconfinedii)  Global“chiral”symmetry:exactformasslessquarksiii)  Baryonnumberandaxialcharge(m=0)areconserved

iv)  Scaleinvarianceofquark(m=0)andgluonfieldsv)  DiscreteC,P&Tsymmetries

• QCD‐“nearlyperfect”fundamentalquantumtheoryofquarkandgluonfields(F.Wilczek,hep‐ph/9907340)

• Chiral,Axial,Scaleand(inprinciple)P&Tbrokenbyvacuum/quantumeffects‐”emergent”phenomena

• Whathappensatfinitetemperature&density?

QCD:structure&consequences•  Asympto2cfreedom:

S:Couplingstrengthofgluonsweakeratshortsepara2on

C:Super‐dense&super‐hotQCDma3er

isweaklycoupledgasofquarks&gluons

Gross,Wilczek,Politzer(1973)

Collins‐Perry(1975);Cabibo‐Parisi(1975)

Infraredslavery:S:Lineargrowthofsta2cquark‐an2‐quarkpoten2alatlargesepara2on‐intui2vepictureofconfinement

C:QCDma3erisstronglyinterac2ngatlowertemp.&density‐RichQCDPhaseDiagram

Wilson(1974),Polyakov,…

(Broken)ChiralsymmetryS:spontaneouslygeneratedChiralcondensateC:ChiralsymmetryrestoredatfiniteT

Nambu‐Goldstone

FromE.Fermi:“NotesonThermodynamicsandSta2s2cs”(1953) Ma3erinunusualcondi2ons

Hagedorn(1965)

Lee‐Wickma3er(1974)

Collins‐Perry/Cabibbo‐Parisi(1975)

Quark‐GluonPlasma(QGP)Shuryak(1978)

QCD:briefpre‐history

NeutronStars BigBang RHIC

Color Glass

Condensates

Initial

Singularity Glasma sQGP -

perfect fluid!Hadron Gas

t

StandardmodelofHICollisions

•  Though broad outlines could be guessed, current understanding far beyond anything anticipated when RHIC was proposed

•  Solidify, Improve, Falsify ?

GluonSatura2oninanucleus:classicalcoherencefromquantumfluctua2ons

Wee parton fluctuations time dilated on strong interaction time scales

Parton momentum fraction / Proton momentum fraction

Parton Density

The gluon density saturates at a maximal value of ~ 1/αS

gluonsatura2on

Largeoccupa2on#=>classicalcolorfields 1/QS

2

Many‐bodyhighenergyQCD:TheColorGlassCondensate

•  Physicshighlynon‐perturba2ve,butcanbedescribedinweakcoupling

‐‐novelregimeofQCD

nuclear size energy

reso

lutio

n

• QCDframeworktounderstandstronglycorrelatedweegluonsinnucleiandtheirevolu2onwithenergy

• Dynamicscharacterizedprimarilybyoneuniversalsemi‐hardscale‐‐thesatura2onscaleQA

S

•  Powerfulanalogytoreac2on‐diffusionprocessesinsta2s2calmechanics

EvidenceforSatura2on@RHIC?  Rich Deuteron+Gold physics program

Δφ=0 (near

side) Δφ=π (away

side)

(rad)

CGC estimates for A+A bulk #’s and trends

Away side parton randomized by strong color field

StandardmodelofHICollisions

Color Glass

Condensates

Initial

Singularity Glasma sQGP -

perfect fluid!Hadron Gas

t

Glasma (\Glahs-maa\): Noun: non-equilibrium matter between Color Glass Condensate (CGC)& Quark Gluon Plasma (QGP)

The big role of wee glue

  What is the role of wee partons ? ✔

  How do the wee partons interact and produce glue ? ✔

  Can it be understood ab initio in QCD ? ✔

Bj, DESY lectures (1975)

ClassicalfeaturesoftheGlasma

Solu2onsofYang‐Millsequa2onsproduce(nearly)boostinvariantgluonfieldconfigura2ons:“Glasmafluxtubes”

Lumpygluonfieldsarecolorscreenedintransverseplaneoverdistances~1/QS‐Nega2veBinomialmul2plicitydistribu2on.

“Glasmafluxtubes”havenon‐triviallongitudinalcolorE&Bfieldsatearly2mes‐‐generateChern‐Simonstopologicalcharge

TheRidge:Glasmafluxtubes+RadialflowAu+Au 200 GeV, 0 - 30% PHOBOS

ηΔφΔ ddNd

N1 ch

2

trig

Δφ

0-5%

STAR Preliminary

p+p

A+A

Longrangerapiditycorrela2onsaresensi2vetoGlasmadynamicsatearly2mesGlasmafluxtubesprovidethelongrangerapiditycorrela2onRadial(“Hubble”)flowofthetubesprovidestheazimuthalcollima2on

13

ChiralMagne2cEffect:Localstrongparityviola2on

L or B

+ External (QED) magnetic field

Chiral magnetic effect

= STAR Preliminary

Possible experimental signal of charge separation

Topological fluctuations -sphaleron transitions in Glasma -as in EW baryogenesis

NCS = -2 -1 0 1

2

Effect most significant, for transitions at early times

StandardmodelofHICollisions

Color Glass

Condensates

Initial

Singularity Glasma sQGP -

perfect fluid!Hadron Gas

t

• Thermaliza2onofGlasmas2llnotunderstood

• Fastisotropiza2onmayoccurduetoinstabilityinducedfieldamplifica2on‐veryanalogousto“prehea2ng”phenomenonininfla2onarycosmology

• Glasmaprovidesini2alcondi2onsforhydrodynamicflow

Strongflow=(nearly)idealhydrodynamics

dN

dy p!dp!d!=

1

2"

dN

dy p!dp!(1 + 2 v2(p!) cos 2(!!!RP) + · · · )

Spatial anisotropy

v2atRHICislarge(BarbaraJacak’stalk)–hydroflowmustsetinearly

v2measureshowefficientlyhotma3erconvertsspa2alanisotropiestomomentumanisotropy–mostefficientwayishydrodynamics

AperfectfluidatRHIC

“BjorkenHydrodynamics” d!

d"= !

!!+ P ! 4

3!"

"

"

Viscoustermsmallerthanidealtermfor!

"+ P

1

#! !

s

1

#T<< 1

Fromkine2ctheory !

s! !

kB

"relax."quant.

H2O 4He6Li sQGP

AdS/CFTandtheKSSboundAdS/CFTconjecture:

DualitybetweenstronglycoupledN=4supersymmetricYang‐MillstheoryatlargecouplingandNc&classical10dimensionalgravityinthebackgroundofD3branes

KSSbound:

Classicalabsorp2oncross‐sec2onofagravitonwithenergyωonablackbrane

!(") =8#G

"

!dtdx ei!t![Txy(t,x), Txy(0, 0)]"

FromKubo: ! ="(0)

16#G

Theorem: !(0) = a

FromBeckenstein:s =a

4Gwherea=areaofblackbrane

Puyngitalltogether:!

s! !

kB

1

4"

η/sandviscoushydro@RHIC

• η/sfromcomparisonsofviscoushydrocodestoRHICdatasuggestitnearlysaturatestheKSSbound–perfectfluid

• Quan2ta2vevaluequitesensi2vetoini2alcondi2ons–Glasma!

• Probablysafetosayitslowerthananyfluidwithpossibleexcep2onofcold6Liatomsintheunitaritylimit(Feshbachresonance)

Viscosityfromperturba2vees2matesissignificantlylarger

Perfectfluiditywithoutthermaliza2on?

!Tµ!"|resum.[A] =

![da]G[a]Tµ!

LO[A+ a]

• Leadingcontribu2ontoquantumevolu2onofTμνcanbere‐expressedasclassicalevolu2onaveragedoverensembleofquantumfluctua2ons

0.1

1

10

100

1000

0 20 40 60 80 100 120 140 160 180 200time

!4 potential, longitudinal expansion

T00 / 3|Tzz| w/o fluctuations|Tzz| with fluctuations

"-4/3i)Phasedecoherenceleadsrapidlytoperfectfluidity=>largeflow

ii)Thesequantumfluctua2onsmayalsoberesponsibleforsphalerontransi2onsgivingrisetotheChiralMagne2cEffect

HardProbesofthesQGP

High pT (>> T) hadrons, heavy mesons (charm and beauty), J/ψ and Upsilon, hard photons and JETS…

dtd

zQzD

QxQxdxdxdpdE c

abcaBbaAaba

σπ

µµφµφ

σ π ˆ),,(),,(),,(

2/2

/2

/3

30

∑∫=

φa/A

φb/B

A

B

abσ̂

D(z)

TheppBenchmark

pQCDworksexcep2onallywell@RHICtofairlylowpT

Partonenergyloss

dE

dz= !!SNc

4p2!

p2! = q̂ L

Characterizesproper2esofhotmedium

q̂Widedispersionintheoryes2matesIdeal gas

WeakversusStrongcouplinginthesQGPWeakcouplingapproachesfitthejetquenchingdata‐‐however,computa2onsarenotundercontrol&largeheavyquarkenergylossisdifficulttoreconcile

LargeenergylossforlightandheavyquarksnaturalinAdS/CFTapproach

ButnojetsinAdS! 6/5/10 6:52 PMPhysics - Figure for Synchrotron radiation from a single quark

Page 1 of 1http://physics.aps.org/view_image/3656/medium/1

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Synchrotron radiation from a single quark

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Synchrotronradia2oninAdSmaybemorelikeinQCD‐collimatedjets

Lotsofexci2ngideasbutnoclearpictureoftransportinsQGP

Outlook

•  WenowhaveastandardmodelofHIcollisionswithunan2cipatedfeaturesliketheCGC,theGlasma&sQGP

•  ThesQGPproducedatRHICmaybethemostperfectfluidinnature

•  Manyapproachestounderstandandquan2fythe

proper2esofthesQGP–butnoconsensusyet

•  NearlyeverythingsaidheremayhavetoberevisedoncedatafromtheLHCPb+Pbbecomeavailable

THE END

THANK YOU!

Strongflow=(nearly)idealhydrodynamics • QCDHydrodynamics=lowenergyeffec2vetheoryofQCDvalidatlargedistances(L>>λmfp)

• Rela2vis2chydrodynamics:Conserva2onlaws

!µTµ! = 0 !µj

µ = 0

• Cons2tu2veequa2ons: Tµ! = (!+ P )UµU! + Pgµ!

jµ = nUµ+!µ!

+!µ

• Dissipa2veterms: ! ij = !"

!#iU j + #jU i ! 2

3$ij %" · %U

"! & $ij %" · %U

Shearviscosity Bulkviscosity!i = !"T#i! µ

T

"

Conduc2vity(diffusion)