The Bulk System at RHIC
Mike Lisa
Ohio State University
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
1
The real issue…
• What happens when nuclei collide?
• important for experiment design
• (also, it’s fun to study in detail!)
• otherwise, who cares?
The real issue is…
• Can we use them to make a
new type of matter in the lab?
• i.e. can we reach  ≥ 1 GeV/fm3 ?
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
2
11 Physics Questions for the New Century
Feb 2002 issue
Based on NRC report
Quarks to Cosmos
2-7 Sept 2006
1. What is dark matter?
2. What is dark energy?
3. How were the heavy elements from iron to
uranium made?
4. Do neutrinos have mass?
5. Where do ultra-energy particles come from?
6. Is a new theory of light and matter needed to
explain what happens at very high energies and
temperatures?
7. Are there new states of matter at ultrahigh
temperatures and densities?
8. Are protons unstable?
9. What is gravity?
10. Are there additional dimensions?
11. How did the Universe begin?
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
3
11 Physics Questions for the New Century
Feb 2002 issue
Based on NRC report
Quarks to Cosmos
2-7 Sept 2006
1. What is dark matter?
2. What is dark energy?
3. How were the heavy elements from iron to
uranium made?
4. Do neutrinos have mass?
5. Where do ultra-energy particles come from?
6. Is a new theory of light and matter needed to
explain what happens at very high energies and
temperatures?
7. Are there new states of matter at ultrahigh
temperatures and densities?
8. Are protons unstable?
9. What is gravity?
10. Are there additional dimensions?
11. How did the Universe begin?
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
4
The real issue…
• What happens when nuclei collide?
• important for experiment design
• (also, it’s fun!)
• otherwise, who cares?
• Can we use them to make a
new type of matter in the lab?
• important for accelerator design
• important for propaganda
• in itself: who cares?
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
5
The real issue…
• Can we use them to make a
new type of matter in the lab?
• important for accelerator design
• important for propaganda
• in itself: who cares?
critical point ?
quark-gluon plasma
Tc
Temperature
• What happens when nuclei collide?
• important for experiment design
• (also, it’s fun!)
• otherwise, who cares?
colour
superconductor
hadron gas
nucleon gas
nuclei
CFL
r0
baryon density
The real issue is…
• What are the properties of this new
state of matter? (T, P, , …)
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
6
The real issue…
• Can we use them to make a
new type of matter in the lab?
• important for accelerator design
• important for propaganda
• in itself: who cares?
critical point ?
quark-gluon plasma
Tc
Temperature
• What happens when nuclei collide?
• important for experiment design
• (also, it’s fun!)
• otherwise, who cares?
colour
superconductor
hadron gas
nucleon gas
nuclei
CFL
r0
baryon density
• What are the properties of this new
state of matter? (T, P, , …)
• important for analysis design
• in itself: who cares?
The real issue is…
• … to use the QGP to understand
hadronization / mass generation
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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The real issue…
• Can we use them to make a
new type of matter in the lab?
• important for accelerator design
• important for propaganda
• in itself: who cares?
• What are the properties of this new
state of matter? (T, P, , …)
• important for analysis design
• in itself: who cares?
80’s-90’s
2000-2004
~now
Temperature
• What happens when nuclei collide?
• important for experiment design
• (also, it’s fun!)
• otherwise, who cares?
critical point ?quark-gluon plasma
Tc
hadron gas
nucleon gas
colour
superconductor
nuclei
CFL
r0
The real issue is…
• QGP as calibrated tool to understand
hadronization / mass generation /
confinement
2-7 Sept 2006
baryon density
will take time...
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Filled in outline
• Motivation and concepts
• Main results and lessons
• soft sector [pT < 2 GeV/c]
• yields
• flow/collectivity: momentum- &
coordinate-space
• firm sector [2 GeV/c < pT < 6 GeV/c]
• baryon/meson systematics
• hard sector
• differential yield suppression
• Summary
high-pT (“hard”)
low-pT (“soft”)
mid-pT (“firm”)
0
5
10
15
pT (GeV/c)
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimentalPHENIX
highlightsPRL 91 241803 (2003) 9
Soft sector - ashes of the QGP
time (1/T)
pdf
pQCD
QGP?
• high-pT tail (“pQCD”) not thermalized
• medium (?) itself decays into low momentum
particles (“soft sector”)
• QGP is non-perturbative, low-Q
phenomenon (need expt’l info)
• dynamics - difficult but crucial here
• Is it a “big” “system/medium”?
• bulk, collective behaviour
• Thermo properties
hadronization
rescattering
99.5%
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
• potentials, temperature (EoS)
• How does it evolve in spacetime?
• dynamic Quark
response
to pressure, (EoS)
2-7 Sept 2006
Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Heavy Ion Collisions dominated by Geometry
Impact parameter vector b :
 beam direction
connects centers of colliding nuclei
b = 0  “central collision”
many particles produced
“peripheral collision”
fewer particles produced
b
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Day-1 estimate of : RHIC might “work!”
Bjorken-Formula for Energy Density:
PRD 27, 140 (1983) – watch out for typo (factor 2)
 Bj
1 1 dET

p R 2  0 dy
~6.5 fm
Time it takes to
thermalize system
(0 ~ 1 fm/c)
pR2
dz   0 dy
Note: 0 (RHIC) < 0 (SPS)
commonly use 1 fm/c in both cases
2-7 Sept 2006
Central Au+Au (Pb+Pb) Collisions:
17 GeV: BJ  3.2 GeV/fm3
130 GeV: BJ  4.6 GeV/fm3
200 GeV: BJ > 5.0 GeV/fm3
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Chemical freezeout
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Chemical freezeout
2-7 Sept 2006
J. Stachel, Quark Matter ‘99
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Careful: need not be “system” “thermalization”
Nice starting point but...
Resonance Suppression
System equilibration and
response to extreme conditions (EoS)
Strangeness Enhancement
probed
by dynamics

pp, AuAu described by same T,  (also e+e- cf Becattini & Heinz 1997)
 phasespace dominance? / “born” into max entropy?

differences
 “strangeness enhancement” (loss of canonical suppression) in AA
 measured short-lived resonance yields suppressed (hadronic rescattering)
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Impact parameter & Reaction plane
Impact parameter vector b :
 beam direction
Reaction plane:
spanned by beam direction and b
connects centers of colliding nuclei
b = 0  “central collision”
many particles produced
“peripheral collision”
fewer particles produced
b
2-7 Sept 2006
bb
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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How do semi-central collisions evolve?
1) Superposition of independent p+p:
momenta pointed at random
relative to reaction plane
b
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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How do semi-central collisions evolve?
1) Superposition of independent p+p:
high
density / pressure
at center
momenta pointed at random
relative to reaction plane
2) Evolution as a bulk system
Pressure gradients (larger in-plane)
push bulk “out”  “flow”
“zero” pressure
in surrounding vacuum
more, faster particles
seen in-plane
b
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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How do semi-central collisions evolve?
1) Superposition of independent p+p: N
momenta pointed at random
relative to reaction plane
0
p/4
p/2
0
p/4
p/2
3p/4
p
3p/4
p
-RP (rad)
2) Evolution as a bulk system
Pressure gradients (larger in-plane)
push bulk “out”  “flow”
more, faster particles
seen in-plane
2-7 Sept 2006
N
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
-RP (rad)
19
Azimuthal distributions at RHIC
STAR, PRL90 032301 (2003)
b ≈ 6.5 fm
b ≈ 4 fm
“central” collisions
midcentral
collisions
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Azimuthal distributions at RHIC
STAR, PRL90 032301 (2003)
b ≈ 10 fm
b ≈ 6.5 fm
b ≈ 4 fm
peripheral collisions
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Elliptic flow v2
N
STAR, PRL90 032301 (2003)
b ≈ 10 fm
b ≈ 6.5 fm
b ≈ 4 fm
4v2
2) Evolution as a bulk system
Pressure gradients (larger in-plane)
push bulk “out”  “flow”
more, faster particles
seen in-plane
2-7 Sept 2006
symmetry, thermal smearing
v2(pT,m) consistent with
anisotropic velocity field
(i.e. property of bulk)
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Elliptic flow – collectivity & sensitivity to early system
“Elliptic flow”
Hydro: P. Huovinen, P. Kolb, U.
Heinz
• Bulk collective motion
• x anisotropyp anisotropy
• sensitive to early pressure
• evidence for
• early thermalization
• QGP in early stage
• large latent heat ?? (Huovinen ‘05)
  10 GeV/fm3
Hydrodynamic
calculation of
system evolution
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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RHIC energies: the first quantitative success of hydro
Elliptic flow – collectivity & sensitivity to early system
• direct access to EoS (phase transitions, lattice, etc.)
Hydro: P. Huovinen, P. Kolb, U.
“Elliptic flow”
Heinz
• Bulk collective
motion
D. Teaney, BerkeleySchool 2005
• x anisotropyp anisotropy
• sensitive to early pressure
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
• evidence for
• early thermalization
• QGP in early stage
• large latent heat ?? (Huovinen ‘05)
  10 GeV/fm3
EoS: P versus  versus n
Hydrodynamic
calculation of
system evolution
2-7 Sept 2006
(Heinz et al)
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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It’s not just good, it’s... perfect!
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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It’s not just good, it’s... perfect!
Kovtun, Son, Starinets 2005
(only?) “ideal” hydro works
finite viscocity lowers v2
2-7 Sept 2006
is QGP “too” perfect?
challenging a proposed bound?
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Hydromania - careful...
• single-point agreement - red flag in
H.I. physics
STAR, PRL86 402 (2001)
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Hydromania - careful...
• single-point agreement - red flag in
H.I. physics
• Detailed agreement between ideal
hydro and measured v2(mass,pt) an
accident?
• only works for “unrealistic” EoS
Huovinen 2005
• late-stage effects
Hirano and Gyulassy; nucl-th/0506049
• initial anisotropy uncertain
Hienz & Kuhlman (2006)
H:
pure hadronic
qp: “lattice”
2-7 Sept 2006
Q:
1st order [“standard”]
T:
“1st order” + slow
approach to SB limit
P. Huovinen,
NPhighlights
A761 296 (2005)
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC
experimental
28
Hydromania - careful...
• single-point agreement - red flag in
H.I. physics
• Detailed agreement between ideal
hydro and measured v2(mass,pt) an
accident?
• only works for “unrealistic” EoS
Huovinen 2005
• late-stage effects
Hirano and Gyulassy; nucl-th/0506049
• initial anisotropy uncertain
Hienz & Kuhlman (2006)
• Claims of perfection may be premature
• Viscous hydro / theoretical systematic
errorbars required to extract physics
from this dominant observable
• but, “s” in sQGP is justified (and, actually
expected from Lattice, in retrospect)
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
29
Geometrical consequences of flow: femtoscopy (“HBT”)
C2(Qinv)
separation
distribution
from
momentum
correlations
R~1/QCORR
2-7 Sept 2006
pa
xa
xb
STAR preliminary
pa
pb
xa
xb
pb
p+p
R ~ 1 fm
Au+Au
R ~ 6 fm
Qinv (GeV/c)
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental
highlights
30
Geometric substructure?
random (non-)system:
all observers measure the
“whole source”
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
31
Flow-generated substructure
random (non-)system:
all observers measure the
“whole source”
Specific predictions of
bulk collective flow:
• space-momentum (x-p) correlations
• faster (high pT) particles come from
•smaller source
•closer to “the edge”
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Flow-dominated
“Blast-wave” model
PRC70 044907 (2004)
R (fm)
Spectra
p
v2
HBT
STAR PRL 91 262301 (2003)
K
2-7 Sept 2006
mT (GeV/c)
space-momentum
substructure mapped in detail
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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So far - response to stimulus
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Jet Tomography - an “external” probe
medium
p+p
=
+
• Simplest way to establish the properties of a system
• Calibrated probe
• Calibrated interaction
• Suppression pattern tells about density profile
• Heavy ion collisions
• Hard processes serve as calibrated probe
• Suppression provides density measure
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Calibrated probe?
• we will compare A+A to p+p, which is
well-measured & under control
p+p→p0+X
S.S. Adler et al, PRL 91 241803
0
5
10
15
pT (GeV/c)
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Calibrated probe?
• we will compare A+A to p+p, which is
well-measured & under control
• penetrating probes created in early
partonic collisions scale according to
binary collisions in A+A
• direct photons
S.S. Adler et al, PRL 94, 232301 (2005)
PHENIX
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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Calibrated probe?
• we will compare A+A to p+p, which is
well-measured & under control
• penetrating probes created in early
partonic collisions scale according to
binary collisions in A+A
• direct photons
• net non-photonic
electrons
we understand rate of
initial, hard processes in A+A
• (also d+Au)...
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
38
5x fewer high pT particles than
“expected” in AuAu
d 2 N AA / dpT d
RAA ( pT ) 
TAAd 2 NN / dpT d
Binary collision scaling
200 GeV p0 RAA
The Ubiquitous RAA…
p+p reference
PHENIX (& all others): PRL 2003
Interpretation
• final state effect is partonic energy loss
in color-charge-dense
(not necc. deconfined) medium
•  = 15 GeV/fm3 @  = 0.2 fm
• ~ consistent w/ BJ and hydro…
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
39
Dainese, Loizides, Paic, EPJ C38(2005) 461
The Ubiquitous RAA…
5x fewer high pT particles than
“expected” in AuAu
d 2 N AA / dpT d
RAA ( pT ) 
TAAd 2 NN / dpT d
Binary collision scaling
p+p reference
Distributions of parton production
points in the transverse plane
Interpretation
• final state effect is partonic energy loss
in color-charge-dense
(not necc. deconfined) medium
•  = 15 GeV/fm3 @  = 0.2 fm
• ~ consistent w/ BJ and hydro…
• Sensitivity actually limited because
medium is so “black”
2-7 Sept 2006
Central RAA Data
Increasing density
Eskola,.
Honkanken,
Salgado,
Wiedemann,
Quark Confinement & the Hadron Spectrum
VII - mike
lisa - RHIC
experimental
highlightsNPA747 (2005) 511 40
Is it “jets” which are quenched? - dihadron correlations
trigger
“trigger”
2-7 Sept 2006
STAR PRL90 082302 (2003)
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
41
Where Does the Energy Go? - look to lower pT
near
• Lower the associated pT to search for
radiated energy
• Additional energy at low pT BUT no longer
collimated into jets
• Active area: additional handles on the
properties of the medium?
• Mach Shocks, Cherenkov Cones …
•e.g. Renk and Ruppert, Phys. Rev. C 73 (2006) 011901
Leading
hadrons
away
Medium
Equilibration
Mach Cone ??
PHENIX preliminary
PHENIX, QM05 and nucl-ex/0507004
STAR,
PRL.
95
(2005)
152301
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
42
anything new in-between?
Probes of the system (hard)
• interesting results
• important open questions
System itself (soft)
• interesting/important results
• important open questions
If we bridge the gap (“firm”)?
?
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
43
Connecting the sectors
soft-firm connection: v2
• hydro breaks down above
~ 2 GeV/c (expected)
• mass systematic
meson/baryon
systematic?
• definitely not hydro!
v2 generated
by anisotropic
energy loss?
symmetry, thermal smearing
P.
2-7Sorensen,
Sept 2006SQM04Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
44
Connecting the sectors
soft-firm connection: v2
• hydro breaks down above
~ 2 GeV/c (expected)
• mass systematic
meson/baryon
systematic?
• definitely not hydro!
v2 generated
by anisotropic
energy loss?
hard-firm connection:
RPID-differential
AA
meson/baryon systematic!
BUT!…
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
45
meson/baryon (i.e. constituent quark
number) systematics suggest…
coalescence (“recombination”) of
already-flowing (!!) partons (*)
PRL 92
92 (2004)
(2004) 052302
052302
PRL
Non-hydro / non-E
origin of firm v2?
v 2hadron( pThadron)  nv 2quark( pTquark)
pThadron  npTquark
*2-7well,
constituent
P. Sorensen,
SQM04
Sept 2006
Quark quarks
Confinement & the Hadron
Spectrum
VII - mike lisa - RHIC experimental highlights
46
A growth industry...
Many model variants
Lin, Molnar, Pratt,
Fries, Bass, Mueller,
Ko, Das, Levai, Hwa,
Greco, Voloshin, Nonaka…
… for a thermal source
Fragmentation wins
out for a power law
tail
Baryons compete with
mesons
Many schemes, all describe
“anomalous” B/M, RAA, v2
But, data themselves (IMHO)
clearly indicate exciting,
collective partonic behaviour
Hope for a “hadronization
testbed”?
2-7 Sept 2006
B. Mueller
Quark Confinement
& theTBS05
Hadron Spectrum VII - mike lisa - RHIC experimental highlights
47
The real issues…
• What happens when nuclei collide?
• high multiplicity, anisotropically distributed
• suppression of high-pT particles
• Can we use them to make a new type of matter in the lab?
• conditions ( and T are right)
• collective effects (flow) = it is a system
• What are the properties of this new state of matter? (T, P, , …)
• source sizes ~6-10 fm
• explosive: huge flow, short timescales
•  ~ 10 GeV/fm3
• “low” viscosity
• strongly coupled
• collective; partonic d.o.f. (?)
The real issue is…
• QGP as calibrated tool to understand
hadronization / mass generation / confinement................ stay tuned!
2-7 Sept 2006
Quark Confinement & the Hadron Spectrum VII - mike lisa - RHIC experimental highlights
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