Evidence for a Quark-Gluon Plasma at RHIC
Part 2
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Creating and Probing the
Quark-Gluon Quagmire at RHIC
John Harris (Yale)
John Harris
Yale University
Lake Louise Winter Institute, 18 – 23 February 2006
On the “First Day” (at RHIC)
PHOBOS
Initial Observations:
Large produced particle multiplicities
ed. - “less than expected! gluon-saturation?”
 dnch/dh |h=0 = 670, Ntotal ~ 7500
Au + Au
CGC?
> 15,000 q +q in final state, > 92% are produced quarks
Large energy densities (dn/dh, dET/dh)
 e  5 GeV/fm3
e  5 - 15 ecritical
PHENIX
30 - 100 x nuclear density
Large collective flow
ed. - “completely unexpected!”
 Large early pressure gradients, energy & gluon densities
 Hydrodynamic & requires quark-gluon equation of state!
Quark flow & coalescence  constituent quark degrees of freedom!
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
1
On the First Day at RHIC - Azimuthal Distributions
STAR, PRL90 032301 (2003)
b ≈ 10 fm
b ≈ 6.5 fm
b ≈ 4 fm
peripheral collisions
Top view
Beams-eye view
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
1
Early Pressure in System
 Elliptic Flow!
z
y
x
Sufficient interactions early (< 1 fm/c) in system
 to respond to early pressure!
 before self-quench (insufficient interactions)!
System is able to convert original spatial ellipticity
 momentum anisotropy!
Sensitive to early dynamics of system
p
p
Azimuthal anisotropy
(momentum space)
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
1
Elliptic Flow Saturates
Hydrodynamic Limit
z
• Azimuthal asymmetry of charged
particles:
dn/df ~ 1 + 2 v2(pT) cos (2 f) + ...
y
x
Mass dependence of v2
Requires • Early thermalization
(0.6 fm/c)
curves = hydrodynamic flow
zero viscosity, Tc = 165 MeV
• Ideal hydrodynamics
(zero viscosity)
 “nearly perfect fluid”
• e ~ 25 GeV/fm3 ( >> ecritical )
• Quark-Gluon Equ. of State
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
If baryons and mesons form
from independently flowing quarks
then
quarks are deconfined
for a brief moment (~ 10 -23 s), then hadronization!
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Universality of Classical Strongly-Coupled Systems
Transport in gases of strongly-coupled atoms
RHIC fluid behaves like this –
a strongly coupled fluid.
Universality of classical strongly-coupled systems?
 Atoms, sQGP, AdS/CFT……
Ultra-low (Shear)Viscosity Fluids
4p  h/s
h/s (water) >10
h/s (limit) = 1/4p
Quantum lower viscosity bound: h/s > 1/4p
QGP
(Kovtun, Son, Starinets)
From strongly coupled N = 4 SUSY YM theory.
2-d Rel Hydro describes STAR v2 data with h/s  0.1 near lower bound!
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Ultra-low Viscosity Fluids
Scientific American, November 2005
“A testholes
comes
from
….. Asmall
preliminary
analysis –
ofsmaller
these experiments
indicates
“Black
have
anRHIC
extremely
shear viscosity
than any known
fluid…
the collisions
are creating
a fluid
with very
lowTviscosity.”
Strongly
interacting
quarks and
gluons
at high
should also have a very low viscosity.”
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
“The RHIC fluid may be the
least viscous non-superfluid 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/
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
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)  mB ~ 25 - 40 MeV
Chemical Freezeout Conditions  T = 177 MeV, mB = 29 MeV  T ~ Tcritical (QCD)
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
QCD Phase Diagram
At RHIC:
T = 177 MeV
T ~ Tcritical (QCD)
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Particles are thermally distributed and flow collectively,
at universal hadronization temperature T = 177 MeV!
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Probing Hot QCD Matter with Hard-Scattered Probes
leading particle
hadrons
hadrons
leading particle
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
High Momentum Hadrons Suppressed - Photons Not
Deviations fromdevbinary scaling of hard collisions: RAA
p /
N AA

N coll N ppp/ 
Photons
Hadrons
factor 4 – 5
suppression
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Final State Suppression / Initial State Enhancement!
• The hadron spectra at RHIC from p+p, Au+Au
and d+Au collisions establish existence of
early parton energy loss, a new final-state effect,
from strongly interacting, dense QCD matter in
central Au-Au collisions
Au + Au Experiment
Final Data
John Harris (Yale)
d + Au Control Experiment
Final Data
Lake Louise Winter Institute, 18 – 23 February 2006
Energy Loss of Hard Scattered Parton
dev
Energy loss requires
large qˆ  5 -10 GeV2 /fm
(Dainese, Loizides, Paic, hep-ph/0406201)
RHIC data
sQGP
QGP
R. Baier
Pion gas
pT = 4.5 – 10 GeV/c
Cold nuclear matter
Much larger energy loss
than expected from
perturbation theory
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Heavy Charm and Beauty Quarks
Heavy quarks thought too massive to be attenuated by medium!
Au + Au  non-photonic electrons
Late
Breaking
News
Single non-photonic electrons (from D and B mesons)
→ suppressed!
Heavy quarks flow like light quarks!
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Hard Scattering (Jets) as a Probe of Dense Matter II
STAR p + p  jet event
JetSTAR
eventAu+Au
in e+e-(jet?)
collision
event
Can we see jets in high energy Au+Au?
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
STAR Hard Scattering: Two-Particle Azimuthal Correlations
Technique:
C2 () 
1
N tri gger
Azimuthal correlation function
Trigger particle
pT > 4 GeV/c
Associate tracks
2 < pT < pT(trigger)
John Harris (Yale)
1
d( h )N(,h )

efficiency
di-jets from p + p at 200 GeV
Lake Louise Winter Institute, 18 – 23 February 2006
STAR Hard Scattering: Two-Particle Azimuthal Correlations
Technique:
C2 () 
1
N tri gger
Azimuthal correlation function
Trigger particle
pT > 4 GeV/c
Associate tracks
2 < pT < pT(trigger)
1
d( h )N(,h )

efficiency
130 GeV Au + Au, central trigger
h < 0.5
h > 0.5
short range h correlation:
jets + elliptic flow
long range h correlation:
elliptic flow
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Relative Charge Dependence
Compare ++ and - correlations to +System
(+-)/(++ & --)
p+p
2.7+-0.6
0-10% Au+Au
2.4+-0.6
Jetset
2.6+-0.7
STAR Preliminary
@ 200 GeV/c
Strong dynamical
charge
0-10% most central Au+Au
correlations in
jet
fragmentation
p+p
minimum
bias
4<pT(trig)<6 GeV/c
 “charge ordering”
2<p (assoc.)<pT(trig)
T
|h|<0.5 - |h|>0.5 (scaled)
Au+Au
|h|<0.5 - |h|>0.5 (scaled)
Au+Au
0<|h|<1.4
p+p
0<|h|<1.4
p+p
Ref: PLB 407 (1997) 174.
pT > 4 GeV/c particle production mechanism same in central Au+Au & pp
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Using p+p to Study Au+Au Jet Correlations
C2 (Au + Au)  C2 ( p + p) + A * (1+ 2v 22 cos(2f ))
STAR 200 GeV/c
peripheral & central Au+Au
p+p minimum bias
4<pT(trig)<6 GeV/c
2<pT(assoc.)<pT(trig)
Central Au Au
+ Au
Peripheral
+ Au

Assume:
high pT triggered Au+Au event
is a superposition:
high pT triggered p+p event +
elliptic flow of AuAu event
– v2 from reaction plane
analysis
– A from fit in non-jet
region (0.75 < |f| < 2.24)
Away-side jet disappears
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Hammering the Nail in the Coffin
Au + Au
away-side correlation
quenched!
no jet quenching!
d + Au
“di-jet” correlations
similar to p + p
Pedestal&flow subtracted
Quenching of Away-side “jet” is final state effect
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Hard Scattering Conclusions
High Pt hadrons
suppressed in central Au + Au
enhanced in d + Au
Back-to-back Jets
Di-jets in p + p, d + Au
(all centralities)
Away-side jets quenched
in central Au + Au
 emission from surface
x
 strongly interacting medium
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Where Does the Energy Go?
dev
correlations
JetJet
correlations
in in
central
Gold-Gold.
central
Gold-Gold.
proton-proton
reactions.
Away
side
Away
side
jet jet
disappears
for
reappears
in particles
Strong back-topT > 2 GeV
pT >particles
200peaks.
MeV
back
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
Azimuthal Angular Correlations
Lost energy of away-side jet is redistributed to rather large angles!
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Charmonium Suppression - Deconfinement
Color screening of cc pair
results in J/y (cc) suppression!
c
Late
News
c
J/y suppressed
but less than expected?
(more to do!)
John Harris (Yale)
Suppression Factor
Color Screening
Lake Louise Winter Institute, 18 – 23 February 2006
Experimental Evidence for Initial State Gluon Saturation
Suppression Factor
Suppression of forward hadrons consistent with saturation of
low-x gluons.
dd
d
x ~ 10-3
x ~ 10-4
Centrality dependence &
x dependence test CGC
x ~ 10-1
John Harris (Yale)
Au
Au
Au
x ~ 10-2
x ~ 10-3
Lake Louise Winter Institute, 18 – 23 February 2006
Summary
Extreme
initial
densities
–
Initial
state
gluon
saturation
3
e  5glass
GeV/fm
(color
condensate?)
~ 30 - rapidities
100 x nuclear
density
forward
 low-x
> d+Au
15,000isqsuppressed
+q in final state
Ideal hydrodynamic flow
→ “perfect fluid”
x ~ 10-3
- Early thermalization &
Quark-Gluon EOS
x ~ 10-4
Au+Au
p+p
Jet energy loss –
large gluon densities 
strongly coupled QGP
Awayside jet
Trigger
jet
Strongly-coupled system of
quarks and gluons (sQGP)
formed at RHIC
Quark coalescence /flow
 constituent quark
degrees of freedom
Equilibrium particle abundances –
Universal hadronization T ~ Tcrit
Rapid u, d, s equilibration near Tcrit
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Signatures & Properties of the QGP at RHIC
• Large e > ec (T > Tc) system – QCD vacuum “melts” – NOT hadrons
• Thermalized system of quarks and gluons – NOT just q & g scattering
Large elliptic & radial flow  fluid flow (“perfect”!)
Heavy quark (charm) flow
Particle ratios fit by thermal model  T = 177 MeV ~ Tc (lattice QCD)
• System governed by quark & gluon Equation of State – NOT hadronic
Flow depends upon particle (constituent quark & gluon) masses
 QGP EoS,, quark coalescence
• Deconfined system of quarks and gluons – NOT hadrons
Flow already at quark level, charmonium suppression (tbd)
• Weakly-interacting QGP (predicted by Lattice QCD) – NOT!!!
Strongly interacting quarks and gluons  ….degrees of freedom (tbd)
• Strongly-interacting QGP (NOT predicted by Lattice QCD)
Suppression of high pT hadrons, away-side jet quenched
Large opacity (energy loss)  extreme gluon/energy densities
 strongly-interacting QGP (sQGP)
John Harris (Yale)
D. Allan Bromley Symposium, 8 - 9 December 2005
Still to do!
Deconfined QGP?
cc, bb suppression &
melting sequence
Chiral symmetry restoration?
Thermalized heavy flavors?
2 AA beauty, multiply-strange baryon production & flow
Opendcharm,
N dydp
T
R

AA
2 pp
AA
Establish
sQGP medium
dproperties
N dydpofT the
N coll
Constituents?
Transport properties (speed of sound, diffusion…)
Flavor dependence of suppression & propagation
Shuryak, QM04
Light vector mesons (mass and width modifications in medium)
Direct Photon Radiation?
New phenomena…….
LHC & 40 x luminosity of RHIC & e-ion collider!
Developments in theory (lattice, hydro, parton E-loss)
(flavor)
“the adventure continues!”
John Harris (Yale)
Lake Louise Winter Institute, 18 – 23 February 2006
Special Thanks for Contributions to This Presentation!!
Mike Lisa
Berndt Mueller
Jamie Nagle
Paul Sorenson
John Harris (Yale)
D. Allan Bromley Symposium, 8 - 9 December 2005