Flow & Correlations in the soft sector @ RHIC
(Selected highlights)
Mike Lisa
Ohio State University
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
1
Relevance of soft physics during high-pT heyday
• recent high-pT results: clearly a very
interesting medium of dense color fields
created in Au+Au @ RHIC
• jet energy loss in medium (QGP?)
p
p
?
pedestal and flow subtracted
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
Au+Au
2
Relevance of soft physics during high-pT heyday
• recent high-pT results: clearly a very
interesting medium of dense color fields
created in Au+Au @ RHIC
• jet energy loss in medium (QGP?)
99.5%
• (rare) high-pT particles are the probes
• evidence in direction of QGP existence
• medium itself decays largely into soft sector
• non-perturbative, low-Q phenomenon
• to understand/study this new system, must
focus on soft sector dynamics/chemistry
(latter discussed previously)
• systematic, detailed studies important here
?
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
Au+Au
3
Bulk system dynamics at RHIC
•
•
•
•
Detailed probes of dynamics through momentum- and coordinate-space
characterization of the source
Central collisions / azimuthally-integrated studies
– p-space: spectra
• collective radial flow (?)
– x-space: two-particle (K-, -) correlations
• collective radial flow (!) [impt to verify]
• timescales
emergence of a
Noncentral collisions / shape analyses
consistent picture?
– p-space: elliptic flow (and beyond!)
• sensitivity to early stage?
– x-space: azimuthally-sensitive  HBT
• detailed handle on anisotropic dynamics
• further constraints on timescales
Summary
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
4
p-space probe of bulk dynamics: -integrated
• spectral shape analysis suggestive of
strong collective radial flow
• important evidence for expanding bulk system
• T falls,  rises with system size
M. Kaneta (old figure)
K. Schweda
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
5
p-space probe of bulk dynamics: -integrated
• spectral shape analysis suggestive of
strong collective radial flow
• important evidence for expanding bulk system
• T falls,  rises with system size
• consistent with hydro/rescattering scenario
• But is it really bulk flow?
• test from space-time side
RHIC
FLOW & HBT 29 oct 2003
Heinz & Kolb, hep-ph/0204061
malisa - DNP03 - Tucson, AZ
6
-integrated x-space probe: K- correlations
• Coulomb FSI  like (unlike) sign charged particles
show (anti-)correlation at small vrel

• sensitive to effective source sizes (homogeneity regions)
• observed at RHIC (Au+Au @ 130 GeV)
• consistent w/flowing source model (BW) &  HBT
rout[]
rout[K]
rout
• bulk collective flow  x-p correlations
• spatial shift between rout[K] and rout[]
• odd terms in rel  rout is measurable
by selecting on sign of vrel
• shift ~consistent w/flowing source model
(same parameters as for spectra, HBT)
Pion slower
RHIC
STAR,&
nucl-ex/0307025
FLOW
HBT 29 oct 2003
Pion faster
Data
Blastwave
r*out (fm) -5.6±0.6
-6.9
malisa - DNP03 - Tucson, AZ
7
-integrated x-space probe:  HBT
• bulk collective flow  x-p correlations
• spatial scale of homogeneity regions (measured by HBT)
decreases with pT
low pT ’s
• observed at RHIC
• roughly consistent w/ flow models w/ same flow as spectra
high pT ’s
consistent, simultaneous description of
spectra, HBT, K-
BUT: imply very short timescales!
Data:
RHICSTAR, PRL 87 082301 (’01)
PHENIX,
88 192032
(’02)
FLOWPRL
& HBT
29 oct
2003
Buda-Lund hydro: Csörgő et al
Fit: Retière & Lisa,
malisa
in prep.
- DNP03 - Tucson, AZ
8
dN/dt
CYM & LGT
Blast-wave
type
fitshadronization
PCM & clust.
0~6-9 fm/c
~0-2 fm/c
NFD
NFD & hadronic TM
string & hadronic TM
PCM & hadronic TM
Data:
RHICSTAR, PRL 87 082301 (’01)
PHENIX,
88 192032
(’02)
FLOWPRL
& HBT
29 oct
2003
time
Buda-Lund hydro: Csörgő et al
malisa - DNP03 - Tucson, AZ
9
ideal, boost-invariant hydro
dN/dt
CYM & LGT
Blast-wave
type
fitshadronization
PCM & clust.
0~6-9 fm/c
~0-2 fm/c
NFD
NFD & hadronic TM
string & hadronic TM
PCM & hadronic TM
time
hydro-inspired “toy” models
• simultaneous description of p- and x-space
• strong collective flow needed
“real” model: ideal boost-invariant hydro
• good job at p-space observables
• fails at x-space observables
• timescale issues?
Heinz & Kolb, hep-ph/0204061
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
10
Alleviations of HBT “puzzles”?
• Experimental: improved treatment of
Coulomb interaction:
STAR 200 GeV central - preliminary
Bowler (’91) & Sinyukov (’98)
urged by CERES (’02)
– in right direction for RO/RS but not
sufficient to match hydro expectation
– no effect on RL problem
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
11
Alleviations of HBT “puzzles”?
• Experimental: improved treatment of
Coulomb interaction:
Bowler (’91) & Sinyukov (’98)
urged by CERES (’02)
– in right direction for RO/RS but not
sufficient to match hydro expectation
RL
RS
– no effect on RL problem
• Theoretical: modify ideal B.I. hydro
– discard Boost-invariance assumption?
• Hirano et al
RO
RO/RS
Hirano & Tsuda, PRC 66 054905 (02)
* implicit in most BlastWave parameterizations
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
12
Alleviations of HBT “puzzles”?
Teaney, nucl-th/0301099
• Experimental: improved treatment of
Coulomb interaction:
Bowler (’91) & Sinyukov (’98)
urged by CERES (’02)
– in right direction for RO/RS but not
sufficient to match hydro expectation
– no effect on RL problem
• Theoretical: modify ideal B.I. hydro
– discard Boost-invariance assumption?
• Hirano et al
– discard zero-viscosity assumption?
• Teaney
• also: Lin, Molnar, Humanic et al
* implicit in most BlastWave parameterizations
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
13
Alleviations of HBT “puzzles”?
Teaney, nucl-th/0301099
• Experimental: improved treatment of
Coulomb interaction:
Bowler (’91) & Sinyukov (’98)
urged by CERES (’02)
– in right direction for RO/RS but not
sufficient to match hydro expectation
– no effect on RL problem
• Theoretical: modify ideal B.I. hydro
– discard Boost-invariance assumption?
• Hirano et al
– discard zero-viscosity assumption?
• Teaney
• also: Lin, Molnar, Humanic et al
v2
– common issue: ability to simultaneously
describe p-space observables also?
* implicit in most BlastWave parameterizations
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
14
Further info – noncentral collisions/shape analyses
• “broken symmetry” for b0 → more detailed, important physics information
• momentum space: increased sensitivity to early stage, EoS
• coordinate space: another handle on dynamical timescales
P. Kolb, nucl-th/0306081
P. Kolb and U. Heinz, hep-ph/0204061
“elliptic flow”
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
15
P-space shape: Flow (radial, directed, elliptic, ...)
y
• Radial flow: Only type of transverse flow in central collision (b=0)
• Integrates pressure history over complete expansion phase
x
x
• Directed flow: probe earliest collision stage (pre-equilibrium, b > 0)
v1
z
y
v2
x
• Elliptic flow: caused by anisotropic initial overlap region (b > 0).
• More weight towards early stage of expansion.

d 3N
1 d 2N 

E 3 
1   2vn cosn( p  RP ) 
dp
2 pT dpT dy  n 1

finer detail ..?
RHIC
FLOW & HBT 29 oct 2003
vn>2
p 
vn  cosn( p  RP )  ,  p  tan 1  y 
 px 
malisa - DNP03 - Tucson, AZ
16
Directed flow at RHIC
• geometric anisotropy in x-z plane
(reaction plane)  p-space anisotropy
• early stage rescattering
RHIC
FLOW & HBT 29 oct 2003
z
x
malisa - DNP03 - Tucson, AZ
17
Directed flow at RHIC
STAR, submitted to PRL
• geometric anisotropy in x-z plane
(reaction plane)  p-space anisotropy
• early stage rescattering
• 1st observation of directed flow at RHIC
• small signal, only away from ycm
• 3-particle cumulants, using strong v2
• [see A. Tang’s talk]
• no obvious “wiggle” (big uncert.)
• comp w/SPS: limiting fragmentation
concept extends to p anisotropy?
• confirms in-plane elliptic flow @
RHIC
• non-BI models needed
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
18
Elliptic flow (v2)
• tremendous amount of
systematics @ RHIC
– , pT, m, centrality
PHOBOS: Phys. Rev. Lett. 89, 222301 (2002)
• sensitive to EoS/QGP
Preliminary v2200
Final v2130
• does B.I. approximation
break down quickly?
200
130
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
19
Elliptic flow (v2) @ RHIC
• tremendous amount of
systematics @ RHIC
R. Snelling, minbias compilation & BW
– , pT, m, centrality
• sensitive to EoS/QGP
• does B.I. approximation
break down quickly?
• pT, m systematics for
wide range of particles
reasonably described at
low-pt with common set
of parameters
STAR & PHENIX (squares)
– x-space anisotropy
indicated
• v2 is BIG! (~2x more
particles in-plane than
out @ pT>1 GeV)
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
20
Higher order flow coefficients?
P. Kolb: “v4 - a small, but sensitive observable for heavy ion collisions”
PRC 68, 031902(R)
•
Strong potential to constrain model calculations and carries valuable information on the
dynamical evolution of the system
•
Magnitude, and even the sign, sensitive to initial conditions of hydro
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
21
Higher order flow coefficients!
cumulant analysis  v4, v6 !!!
STAR, submitted to PRL
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
22
Freeze-out anisotropy as an evolution “clock”
hydro evolution
later hadronic stage?
Teaney et al, nucl-th0110037
• dilute (hadronic) stage
• little effect on p-space at RHIC
• significant (bad) effect on HBT radii
• related to timescale
• qualitative change in FO
in-planeextended
P. Kolb and U. Heinz,
hep-ph/0204061
RS small
• anisotropic pressure gradients
→ preferential in-plane flow (v2)
→ evolution towards in-plane shape
• FO sensitive to evolution duration 0
hydro only
hydro+hadronic rescatt
p=90°
RS big
R.P.
p=0°
STAR
PHENIX
Soff,
Bass,nucl-th/0110037
Dumitru, PRL 2001
Teaney, Lauret,
Shuryak,
out-of-plane-extended
Teaney et al, nucl-th0110037
• FO from asHBT?
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
23
asHBT at 200 GeV in STAR – R() vs centrality
12 (!) -bins b/t 0-180 (kT-integrated)
• clear oscillations observed in transverse radii
• centrality dependence reasonable
• oscillation amps higher than 2nd-order ~ 0
→ extract 0th, 2nd Fourier coefficients vs kT
with 4 -bin analysis
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
24
asHBT at 200 GeV in STAR – R() vs kT
• Clear oscillations observed at all kT
• extract 7 radius Fourier Coefficients
(shown by lines)
2

 R  pT ,   cosn 
R  ,n pT    2
R p ,   sin n 

  T
2
RHIC
FLOW & HBT 29 oct 2003
midcentral collisions (20-30%)
  o, s, l
  os
malisa - DNP03 - Tucson, AZ
25
Estimate of initial vs F.O. source shape

R 2y  R 2x
R 2y  R 2x
• estimate INIT from Glauber
• from asHBT:
 FO  2
R S2, 2
R S2,0
• FO < INIT → dynamic expansion
• FO > 1 → source always OOP-extended
• constraint on evolution time
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
26
A simple estimate – 0 from init and final
• BW → X, Y @ F.O. (X > Y)
• hydro: flow velocity grows ~ t
  X ,Y ( t )   X ,Y (F.O.) 
t
0
• From RL(mT): 0 ~ 9 fm/c
consistent picture
• Longer or shorter evolution times
X inconsistent
P. Kolb, nucl-th/0306081
toy estimate: 0 ~ 0(BW)~ 9 fm/c
• ...but need a real model comparison
→ asHBT valuable “evolutionary clock”
constraint for models
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
27
Broad strokes of the highlights
•
impressive degree of detail in characterization of soft dynamics at RHIC
– , pT, m, centrality, 
– p-space: “v0” through v6 !!!
– x-space: transverse shape analysis !!!
•
from p- and x-space sectors, clear, consistent evidence of bulk flow
•
can be described in simple (simplistic?) BlastWave scenario with short timescales
•
very strong constraints on “real” dynamical models
– new constraints on both early (init conditions) and late (FO) configurations
•
plenty more work to do before we claim to understand bulk dynamics at RHIC
RHIC
FLOW & HBT 29 oct 2003
malisa - DNP03 - Tucson, AZ
28