Experimental Probes of Strongly Coupled Plasmas

(my favorite way to probe my favorite strongly coupled plasma)

outline

What’s a plasma?

Why we think the quark gluon plasma at RHIC is strongly coupled

Other strongly coupled plasmasand their properties

What do we know and what will be measured next?suggest modeling needed to interpret the data

what is a plasma?

4th state of matter (after solid, liquid and gas)

a plasma is:ionized gas which is macroscopically neutralexhibits collective effects

interactions among charges of multiple particlesspreads charge out into characteristic (Debye) length, D

multiple particles inside this lengththey screen each other

plasma size > D

Energy density of matter

high energy density: > 1011 J/m3

P > 1 MbarI > 3 X 1015W/cm2 Fields > 500 Tesla

ideal gas or strongly coupled plasma?

Huge gluon density! estimate = <PE>/<KE>

using QCD coupling strength g<PE>=g2/d d ~1/(41/3T)

<KE> ~ 3T ~ g2 (41/3T) / 3Tg2 ~ 4-6 (value runs with T)

for T=200 MeV plasma parameter

quark gluon plasma should be a strongly coupled plasma

how does it compare to interesting EM plasmas?

> 1: strongly coupled, few particles inside Debye radius

A little more on coupling

potential V s/r <KE> T r=interparticle distanceQCD matter: /r3 3 and so we see that r 1/T

= <PE>/<KE> (s/r)/T sT/T s

T cancels, but does affect s

D = {T/(4e2}1/2 so D {T/(sT3}1/2 1/(Ts1/2)

s

We know 1/ #particles inside Debye volume ND

ND= N/VD= VD VD= 4/3 D3

1/(s3/2T3)

so ND= 1/s3/2 T cancels again

for s large, ND is large (D fairly large, but included in ND)

for s small, ND is small (D smallish)

putting in some numbers

both and ND depend on s

at RHIC dNg/dy ~ 800

so = 800/(1 fm * R2 fm2) = 800/100 = 8 /fm3

r = 0.5

from lattice s= 0.5-1 for quarks

for gluons multiply by 3/(4/3) = 9/4. It’s big! from pQCD s= 0.3 for quarks and ~0.7 for gluons

Lattice says

T/Tc

Karsch, Laermann, Peikert ‘99

/T4

Tc ~ 170 ± 10 MeV

~ 3 GeV/fm3

~15% from ideal gas of weakly interacting quarks & gluons

quite different from ideal gas of q, g!

Lattice also tells us

hadrons don’t all melt at Tc!

c bound at 1.5 Tc Asakawa & Hatsuda, PRL92, 012001 (2004)

charmonium bound states up to ~ 1.7 Tc Karsch; Asakawa&Hatsuda

, survive as resonances Schaefer & Shuryak, PLB 356 , 147(1995)

spectral function

strongly coupled gas of Li atoms

M. Gehm, S. Granade, S. Hemmer, K, O’Hara, J. ThomasScience 298 2179 (2002)

cool the atoms to make KE<PE, excite a resonance

weakly coupled

strongly coupled ↓ ellipticflow!

strongly coupled Astrophysical plasmas

Astrophysical phenomenahow do neutron stars, giant planet cores, gamma ray

bursters, dusty plasmas, jets work?

Fundamental physics questionsproperties of the matter, interactions with energy under

extreme conditions

High Energy Density Physics in Stockpile Stewardship Facilities (NIF, Omega, Z-pinch)

Materials Properties warm, dense matter: behavior between solid, fluid and plasma. found in giant planet cores, laser heated foils

Compressible Dynamics how do strong shocks and high Mach number flows interact with ambient medium: astrophysical jets, black hole accretion disks, ignition targets, weapons…

Plasma properties generally studied

density and opacity electrical and thermal conductivity transport properties

diffusionhydrodynamic expansion velocity, shock propagation

waves in plasma and dispersion relation plasma oscillations and instabilities radiation

bremsstrahlung, blackbody, collisional and recombination

Shock and interface trajectories are measured by x-ray radiography

Slope of shock front yields Us

Slope of pusher interface gives Up

.

Al

D2

time (ns)

shock front

Al pusher

dista

nce (µ

m)

0.0 5.01.0 2.0 3.0 4.0 6.0 7.0 8.0

0

100

200

300

x

L

Lx

=o =

Us

Us-U

p

streak camera record

R. Lee, S. Libby, LLNL

P-P0=0UsUp

of particular interest for strongly coupled plasmas

kinetic energy distribution (T)measure electrons radiated from plasma

flow properties (turbulent and non)measure particle transport using laser induced

flourescenceagain study electron radiation from plasmaopacity to hard x-rays (time resolved)

thermalization timephoton absorption & ion spectrum vs. time

plasma oscillations see density fluctuations in electron arrival times

correlations among particlesmeasure radiated particle pairs

crystallization viscosity

from S. Ichimaru, Univ. of Tokyo

search for collectivity at RHIC

dN/d ~ 1 + 2 v2(pT) cos (2) + …

“elliptic flow”

Almond shape overlap region in coordinate space

x

yz

momentum space

What have we learned already about QGP?

Pressure built up very rapidly during ion collisions at RHIC large collective flow, calculate w/hydrointeraction large, fast thermalizationviscosity small

huge energy loss in fast quarks

traversing mediumenergy, gluon density largemedium is opaque

baryon production enhanced byfactor of 3 compared to p+p

Kolb, et al

at high pT v2 reflects opacity of medium

v2

STAR

approximately expected level from jet quenching

Data are for high pt pi0s, PHENIX, blue cicles – 4.59 GeV/c, green squares – 5-7 GeV/c

No flow needed!

Can calculate elipticity parameter v2 as jet surviving probability in and out of plane

black medium after 2.3 fm/c sQGP formation timeV. Pantuev

picture reproduces other features: reaction plane dependence of Raa away side jet yield

Look in-plane, =0

Look out-plane, =/2

Cutoff L=2.3 fm/c is adjusted for in-plane 50-55% centrality Raa=0.9

Raa() is inclusive measurement and in a particular event you always look at some angle.

x-y projections of Ncoll centers for 40-45% centrality from Glauber model with Woods-Saxon density distribution.

L

V. Pantuev

charm quarks (via nonphotonic electrons)

~ same energy loss as light quarks

e loss not all radiative

show non-zero v2at modest pT

flow? thermalization with the light quarks?

QGP properties

Extracted from models, constrained by dataEnergy loss <dE/dz> (GeV/fm) 7-10 0.5 in cold matter

Energy density (GeV/fm3) 14-20 >5.5 from ET data

dN(gluon)/dy ~1000 From energy loss + hydro

T (MeV) 380-400

Experimentally unknown as yet

Equilibration time0 (fm/c) 0.6 From hydro initial condition; cascade agrees

NB: plasma guys have same problem & same technique

Opacity (L/mean free path) 3.5 Based on energy loss theory

Equation of state? Early degrees of freedom and their ? Deconfinement? Thermalization mechanism? Conductivity?

need good sensitivity to rare probes and improved background rejection for plasma radiation

QGP is not rare in these collisions, but (clean) signals of early-time phenomena ARE!

High pT hadrons, γ + jet, di-jets probe density, gluon bremstrahlungHeavy quarks (bound & unbound) probe screening, thermalizationDirect photons, electrons radiation from plasma

A+A Species scanp+p Energy scand+A High statistics

C,B

the rest of the properties

Jet tomography

correlations of 2, 3 (more?) particles from jets traversing medium

-jet correlations; fixes jet energygq → q

identify the hadrons: hadronization, charm e-loss

increase PHENIX, STAR calorimeter coverage for

upgrade rate capabilities of data acquisition, analysis2007

increased machine luminosity (2013?)

cross section small, so rate is low

M.Miller, QM04

(1/N

trig)d

N/d

()

STAR Preliminary

cGeVp

cGevpassocT

trigT

/42.0

/64

speed of sound via a density wave?

+/-1.23=1.91,4.37 → cs ~ 0.33 (√0.33 in QGP, 0.2 in hadron gas)

PHENIX preliminary

dN

/d()

g radiates energykick particles in the plasmaaccelerate them along the jet

why so many baryons at medium pT?

sensitive probe of hadronizationquark coalescence: good starting point

small production rate → sensitivity to correlations of quarks inside the medium!a tool to probe wakes in the plasma. correlators?

upgrade PID in STAR and PHENIX by ‘09 increased luminosity to allow scanning collision energy,

species (Au+Au, Cu+Cu compare to p+p, d+Au)

jet

par

tner

s p

ertr

igge

r

Npartp+p

all baryons from quarks drawn from the medium

dileptons and photons

pT spectrum of soft * reflects Tinitial

interpretation problem: unfolding time history of the expansionnote: fixing the EOS for hydro is essential!

medium modificationof final vector mesons

decays of bound states?

detector upgrades will reduce decay background and allow measurement of charm background

energy & system size scans require luminosity upgrade

Heavy Quarkonium – a screening probe

map charmonium and bottomonium states to study competition between melting and regeneration

color screening length? Tinitial? upgraded luminosity will allow:

measurement of Y v2 of J/energy scan for J/, screening vs. regeneration

RHIC

counts per yearcomparable to thoseat LHC!

Heavy Quarks – open charm

precision measurements to quantify energy loss and v2 as a function of momentumhow opaque IS the medium?relative role of gluon radiation and collisional energy loss

must measure charm yieldto subtract from intermediate mass dilepton continuum

inner tracker upgrades for PHENIX and STAR needed to tag displaced vertex for clean measurement

ready by 2011

what sQGP plasma properties could these yield?

speed of sound via jet modifications quark correlations in the medium

baryon formationmedium modifications of jet fragmentation

propagation of jet-induced shocks constrain radiative vs. collisional energy loss screening length via onium spectroscopy T via radiated dileptons, photons dissipation via energy flow in shocked medium Would like to identify experimental signatures of

viscosityWeibel instability in first 0.6 fm/c

RHIC II

FY 2006 FY 2007 FY 2008 FY 2009 FY 2010 FY 2011 FY 2012 FY 2013

RHIC Mid-Term Strategic Plan

LHI

LP4

e Cooling CD-0 CD-1 CD-2 CD-3 CD-4

PHENIX + STAR Data-Taking

Hi Rate DAQ 1000

PIDHBD

TOF

VTX

Forward

FMSMu Trigger Nose Cone Calorimeter

EBIS

Heavy Ion Luminosity

SPIN F.O.M.

e-pair spectrum Open Charm Jet Tomography

Mono-JetU+U

PHENIX STAR

G/G P-V W± prod. and Transversity

PHENIX & STAR VTX upgrades

STAR Integrated Tracking

Hydro. CalculationsHuovinen, P. Kolb,U. Heinz

v2 reproduced by hydrodynamics

STARPRL 86 (2001) 402

• see large pressure buildup! • anisotropy happens fast • early equilibration

central

Hydrodynamics can reproduce magnitudeof elliptic flow for , p. Mass dependence requires softer than hadronic EOS!!

Kolb, et al

NB: these calculations have viscosity = 0“perfect” liquid (D. Teaney)

Elliptic flow scales as number of quarks

0 1 2 pT/n (GeV/c)

v2 scales ~ with # of quarks! when the pressure is built up, quarks are the degrees of freedom

suppression persists to 20 GeV/c!

ddpdT

ddpNdpR

TNN

AA

TAA

TAA /

/)(

2

2

nuclear modification factorratio of data on previous slide

interaction of radiated gluons with gluons in

the plasma greatlyenhances the amount

of radiation

Property probed: density

calculate using anopacity expansion

I. Vitev

d+Au

Au+Au

look for the jet on the other sideSTAR PRL 90, 082302 (2003)

Central Au + Au

Peripheral Au + Au

Medium is opaque!

Are back-to-back jets there in d+Au?

Pedestal&flow subtracted

Yes!

no medium ↓

no jet quenching

How to get fast equilibration & large v2 ?

parton cascade using free q,g scattering cross sections doesn’t work! need x50 in medium

Molnar

Lattice QCD shows qqresonant states at T > Tc, also implying high interaction cross sections

Hatsuda, et al.

do heavy quarks lose energy?

e± in Au+Au vs <Ncoll>*p+p

peripheral collisions

central collisions

c quark suppression is nearly as large as for pions!

J. Edgemir, A.Dion, R. Averbeck

where does the lost energy go?

transferred to the plasma? does the medium respond?

look at “away side” jet’s particles at thermal pT

PHENIX preliminary

At RHIC:

CuCu

200 GeV/c

AuAu

200 GeV/c

dAu

200 GeV/c

J/ muon arm

1.2 < |y| < 2.2

mea

sure

d/e

xpec

ted

At RHIC:

CuCu

200 GeV/c

AuAu

200 GeV/c

dAu

200 GeV/c

AuAuee

200 GeV/c

CuCuee

200 GeV/c

J/ muon arm

1.2 < |y| < 2.2

J/ eeCentral arm

-0.35 < y < 0.35

At RHIC:

CuCu

200 GeV/c

AuAu

200 GeV/c

dAu

200 GeV/c

AuAuee

200 GeV/c

CuCu

62 GeV/c

J/ muon arm

1.2 < |y| < 2.2

J/ eeCentral arm

-0.35 < y < 0.35

Factor ~3suppression

in central events

CuCuee

200 GeV/c

At RHIC:

J/ muon arm

1.2 < |y| < 2.2

J/ eeCentral arm

-0.35 < y < 0.35

Factor ~3suppression

in central events

Data show the same trend within errors for all beams and even at √s=62 GeV

RAA

vs Npart

: PHENIX and NA50

NA50 data normalized at NA50 p+p point.

Suppression similar in the two experiments, although the collision energy is 10 times higher (200GeV in PHENIX & 17GeV in NA50)

What suppression should we expect?

Models that were successful in describing SPS datafail to describe data at RHIC

- too much suppression -

can get better agreement with data

if add formation of “extra” J/ by coalescence of c and anti-c from the plasma

caveat: not necessarily unique or correct explanation!

Possibility of plasma instability → anisotropy

small deBroglie wavelength q,g point sources for g fieldsgluon fields obey Maxwell’s equationsadd initial anisotropy and you’d expect Weibel instability

moving charged particles induce B fieldsB field traps soft particles moving in A directiontrapped particle’s current reinforces trapping B fieldcan get exponential growth

(e.g. causes filamentation of beams) could also happen to gluon fields early in Au+Au collision

timescale short compared to QGP lifetimebut gluon-gluon interactions may cause instability to

saturate → drives system to isotropy & thermalization

The Scope of the Tools (!)

STARspecialty: large acceptancemeasurement of hadrons

PHENIXspecialty: rare probes, leptons,

and photons