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Report
Workshop of European Group on Ultrarelativistic Heavy Ion Physics
Close velocity Correlations
JINR, Dubna
9-14. 03. 2006
q
from STAR to ALICE
Jan Pluta, Warsaw University of Technology
The starting point
1972 - 4
Kopylov and Podgoretsky
settled the basics
of correlation femtoscopy:
•correlation function,
•mixing technique,
•role of space-time charakterist...
Podgorecki, Kopylov, Smorodinski
Dubna, 1974
1975 ...
Grishin, propane bubble
chamber group and others in
Dubna - measured the twoparticle correlations
1981
Lednicky and Lyuboshitz
solved the problem of
final state interaction
Weekly meeting of propane
bubble chamber group.
The basic notions
Two-particle interferometry: p-space separation  space-time separation
p

  
x
q
q  p p
1
1
2
qside
Rside
x2
p2
qout
1
 1  
k  p 2  p1 
2
qlong
Rout
• HBT: Quantum interference between identical particles
Gaussian
model (3-d):
– Final-state effects (Coulomb, strong) also can cause
correlations, need to be accounted for
C (q)
P( p1 , p2 )
real event pairs
C ( p1 , p2 ) 

P( p1 )P( p2 ) mixed event pairs
2
2
2
2
2
2
 qout
 
Rout
 qside
Rside
 qlong
Rlong
C (q , k )  1  (k ) e
~
2
1
R
1
q (GeV/c)
HBT at RHIC...
HBT Excitation Function
“RHIC HBT puzzle”
•unexpected (small) sizes
•Rout/Rside = (approx.)1
•Pt dependence do not agree with models
•The same Pt dependence for pp, dAu and AuAu
STAR 130 GeV
PHENIX 130 GeV
Z.Chajęcki, QM’2005
Pion HBT radii from different systems
and at different energies
scale with (dNch/dη)1/3
RHIC/AGS/SPS Systematics
<kT>≈ 400 MeV (RHIC)
<kT>≈ 390 MeV (SPS)
Lisa, Pratt, Soltz, Wiedemann, nucl-ex/0505014
STAR DATA
(pp,dAu,CuCu,[email protected] - prelim.)
System expansion: Initial vs Final Size
Collisions at 200GeV only
Smooth expansion of the
system from p+p to Au+Au
AuAu: system expands
pp (dAu): no or less expansion
Proton initial size = 0.89 fm
from e-scattering
Transverse mass dependence in Au+Au
STAR, [email protected], PRC 71 (2005) 044906
0.
0.
0.
.2
0.2
0.3
0.4
0.5
0.2
0.3
0.4
0.5
0.6
In Au+Au pT (mT) dependence
attributed to collective expansion of
the source
Calc. with Blast-Wave Retiere, Lisa, PRC 70 (2004) 044907
Consistency check on flow – kaons
Hania Gos,
Kromeriz’05
More confirmation
STAR preliminary
Surprising („puzzling”) scaling
 All pT(mT) dependences of
Ratio of (AuAu, CuCu, dAu) HBT
radii by pp
HBT radii observed by STAR
scale with pp although it’s
expected that different
origins drive these
dependences
HBT radii scale with pp
Scary coincidence
or something deeper?
pp, dAu, CuCu - STAR preliminary
Hania Gos,
Kromeriz’05
Adam Kisiel,
Fabrice Retiere
Nonidentical particle correlations –
the asymmetry analysis
Heavier particle
faster
Lighter particle
faster
Catching up
C
-
interaction
time larger
•Stronger correlation
Moving away
C
+
C
Kinematics selection
along some direction
•Effective
+
C
-1
•Effective
Interaction
time smaller
•Weaker correlation
“Double” ratio
•Sensitive
to the space-time
asymmetry in the emission process
e.g. kOut, kSide, cos(v,k)
k*
R.Lednicky, V. L.Lyuboshitz,
B.Erazmus, D.Nouais,
Phys.Lett. B373 (1996) 30.
Pion-Kaon at 200 AGeV
kaon faster
• Good agreement
for same-charge
combinations
pion faster
STAR
preliminary
• Clear emission
asymmetry signal
Out
double ratio
0.9 syst.
Sigma: 17.3 ± 0.8 +- 1.6
syst. fm
6.1 syst.
Mean: -7.0 ± 1.2 +- 4.0
syst. fm
Side
double ratio
Pion-Proton 130 AGeV
• Good agreement
for identical and
opposite charge
combinations
• We observe
Lambda peaks at
k*~decay
momentum of Λ
proton faster
Λ peaks
STAR
preliminary
Side
double ratio
1.0 syst. fm
Sigma: 15.1 ± 0.4 +- 1.5
syst.
1.9 syst.
Mean: -7.4 ± 0.9 -+3.4
syst. fm
Fit assumes source is a
gaussian in r*out
pion faster
Out
double ratio
Hania Gos,
Kromeriz’05
Adam Kisiel, Kromeriz’05
Origins of asymmetry
all
pion
emission
times
primordial
all
kaon
emission
times
primordial
• Measures asymmetry in pair rest frame
is a combination of time and space
shifts in source frame
• In heavy-ion collisions one expects
difference in emission time from
resonance decays
pion average = 16.1
kaon average = 14.8
time shift = 1.3
THERMINATOR
calculation
pion
emission
points
side
kaon
emission
points
Space asymmetry from flow
out
proton
emission
points
THERMINATOR calculation
• Transverse momentum of particles is
composed of the thermal (randomly
distributed) and flow (directed
“outwards”) components
• With no flow average emission point is at
center of the source and the length of
homogeneity is the whole source
• Flow makes the source smaller (“size”-p
correlation) AND shifted in outwards
direction (x-p correlation)
• For particles with large mass thermal
motion matters less – they are shifted more
in “out” direction. The difference is
measured as emission asymmetry.
Fourier coefficients of HBT() oscillations
• Out-of-plane sources at
freeze-out
– Pressure and/or expansion
time was not sufficient to
quench initial shape
• From v2 we know...
– Strong in-plane flow →
significant pressure build-up
in system

R 2y  R 2x
R 2y  R 2x
eccentricity
Ry
Rx
Time
 Short expansion time plays dominant role
in out-of-plane freeze-out source shapes
STAR Collaboration, nucl-ex/0312009
Dmitri Peresounko
Direct photon interferometry
PHENIX; d+Au collisions at √sNN=200 GeV
Paul Chung, Stony Brook
Technique Devised by:
D. Brown, P. Danielewicz,
PLB 398:252 (1997).
PRC 57:2474 (1998).
Emitting source

ImagingTechnique
Inversion of Linear integral
equation to obtain source function
1D Koonin Pratt Eqn.
C (q )  1  4  drr 2 K 0 (q, r )S (r )
Encodes FSI
Correlation
function
Source
function
(Distribution of pair
separations)
Inversion of this integral equation
== Source Function
T.Csorgo,
Kromeriz’05
Rewiew of Bose-Einstein/HBT Correlations
in high energy heavy ion physics
Model F
Model G
Nature hides her secrets in data (D)
Question 0: Do the models (E,F,G,H) describe the data?
Answer 0: These models fail, but this is not a puzzle.
Q. 1: Are any other models that descibe the data?
A. 1: Yes, there are three models (A,B,C) that
cannot be excluded (Conf. Lev. > 0.1 %)
Q. 2: Do these models have anything in common?
A. 2: Yes, and this where the data (D) are.
This common part is what Nature is
trying to tell us.
Model E
Model A
D
Model B
Model C
Model H
Comparison of results of models
Acceptable
Comparison of results of models
Comparison of results of models
Comparison of results of models
Comparison of results of models
Comparison of results of models
Comparison of results of models
Comparison of results of models
Comparison of results of models
Comparison of results of models
Acceptable
Comparison of results of models
Comparison of results of models
~Acceptable
Comparison of results of models
~Acceptable
Comparison of results of models
T.Csorgo, Kromeriz’05
The HBT test
Less unpromising models: don’t fail fitting Au+Au HBT data @ RHIC
– nucl-th/0204054
Multiphase Transport model (AMPT)
Z. Lin, C. M. Ko, S. Pal
– nucl-th/0205053
``
Hadron rescattering model
T. Humanic
– nucl-th/0207016
Buda-Lund hydro (hep-ph/9503494, 9509040)
T. Csorgo, B. Lörstad, A. Ster et al.
(nucl-th/0403074, /0402037, /0311102 )
– hep-ph/0209054
Cracow model (single freeze-out, thermal)
W. Broniowski, A. Baran, W. Florkowski
– nucl-ex/0307026
Blast wave model (Schnedermann, Heinz)
M. A. Lisa, F. Retiere, PRC70, 044907 (2004)
– hep-ph/0404140
Time dependent Duke hydro model
T. Renk
– nucl-th/0411031
Seattle model (quantum opacity)
J. G. Cramer, G. A. Miller, J.M.S. Wu, J.-H. Yoon
– nucl-th/0507057
Kiev-Nantes model
Borysova, Sinyukov, Akkelin, Erazmus, Karpenko
Successfull models at RHIC (1): Blastwave
T=106 ± 1 MeV
<InPlane> = 0.571 ± 0.004 c
Spectra
<OutOfPlane> = 0.540 ± 0.004 c
RInPlane = 11.1 ± 0.2 fm
v2
ROutOfPlane = 12.1 ± 0.2 fm
Life time () = 8.4 ± 0.2 fm/c
Emission duration = 1.9 ± 0.2 fm/c
HBT
2/dof = 120 / 86
(Errors are statistical only, CL = 0.91 %)
Neglect of resonances
F. Retiere, nucl-ex/0405024; F. Retiere and M. A. Lisa, nucl-th/0312024
Successfull model (2): Cracow model
Model features:
Thermal model included
(abundances driven by Tchem and B)
Assumes full Hubble flow
Sudden freeze-out
(at a constant proper-time)
Single freeze-out, Tchem = Tkin
Boost-invariance
nucl-th/0212053
All resonances included,
they decay but do not rescatter.
Future plans at LHC
RHIC/AGS/SPS Systematics
<kT>≈ 400 MeV (RHIC)
<kT>≈ 390 MeV (SPS)
...and expectations
for LHC
Assuming
the same tendency:
40961/3=16
80001/3=20
Rexpected < 10fm
Tom Humanic, Kromeriz’05
Pion freezeout time and z-position for LHC
form rescattering calculations
Pion freezeout times are about twice as long at LHC
compared to RHIC
Two-pion correlation function for LHC
form rescattering calculations
Projected 3D two-pion C2 for
LHC Pb+Pb from rescattering
for b=8 fm centrality and
pT bin 0-200 MeV/c
Transverse radius parameters for LHC
vs. RHIC
Transverse radius parameters are somewhat larger and show a stronger
pT dependence for LHC compared with RHIC
RLong and  parameters for LHC vs.
RHIC
RLong for LHC is almost twice as large as for RHIC reflecting
longer freezeout times;
 behaves about the same at LHC and RHIC
Current status of momentum correlation analysis
Results of PPR preparation; Chapter 6.3 Momentum Correlations
1.
„HBT-analyser” – a dedicated sofrware for momentum coorelation
analysis at ALICE - ready and integrated in Ali-root environment
2.
Experimental factors specific for correlation analysis: track
splitting, merging, two-particle resolution and PD - evaluated for
different two-particle systems
3.
Universal fitting procedure for identical and nonidentical particles
„Corfit” – ready, but not integrated yet in Ali-root environment
4.
Influence of hard processes (jets) on particle correlatins – under
investigations
5.
Single event pion interferometry will be possible at ALICE
Current status of momentum correlation analysis
For details see:
ALICE-INT-2005-026, One and two-particle resolution and PID
ALICE-INT-2005-031, Two-tracks effects at ALICE
ALICE-INT-2005-045, Some specific features of momentum
correlations to be seen at ALICE (draft-0)
• Formalism of two-particle correlations
• Particle correlations for expanding sources
• Role of Coulomb and strong final state interactions
• Nonidentical particle correlations and space-time asymmetries
• Azimuthally sensitive HBT
• Formation of light (anti)nuclei
• Multi-particle Coulomb effects
• Correlation measurements of two-particle scattering
• Influence of resonance decays on two-particle correlations
Some examples
Simulation chain for particle correlations
Piotr Skowroński
Two Particle Resolutions
Resolution (r.m.s) [MeV]
Qinv
Qout
Qside
Qlong
PDC04
TP
PDC0
4
+
0.9
1.3
3.4
3.8
0.4
0.4
1
0.8
K K
2.3
4.2
6.4
9.5
0.6
0.5
1.9
2.3
pp
4.0
8.0
9.4
13.0
0.8
0.7
3.2
4.3
K-
x
x
4.4
4.1
1.2
0.7
1.7
1.1
p
x
x
5.8
4.2
2.1
0.7
1.8
1.2
K p
x
x
6.4
8.3
1.9
1.0
2.6
3.2
TP
PDC04
TP
PDC04
TP
Compare the results presented in „Technical Proposal” (TP, in 1995)
and obtained from PDC04 (in 2005)
Almost the same results after ten years of work – very well ( ! ) :
reasonable first estimation, and very good complete reconstruction.
Track Merging
• Anti-Merging cut as implemented by STAR
– Cutting on average distance between two tracks in TPC
– Space coordinates of tracks are calculated assuming helix shape
using track parameters as reconstructed in the inner part of TPC
Single event pion-pion interferometry (with FSI)...
by Zbyszek Chajęcki,
(ro=8fm)
Single event pion-pion interferometry
by Hania GOS
We are looking forward,
working,
and waiting
for the first event of ALICE
Two-particle kinematics
LCMS: (P1+P2)z=0
Getting quantitative What can be probed through fitting?
Source of
particle 2
Source of
particle 1
r
Separation between
source 1 and 2 in pair
rest frame
Boost to pair rest frame
r [fm]
r* =pairr –pairt
r* separation in pair rest frame
Function of pair(pair)
r* [fm]
When fitting “double-ratios”
two independent variables
are accessible:
- Mean shift (<r*>) or μ
- Sigma (r*)
Two important events;
sources of information
and discussion forum:
Quark Matter Conference
and
satellite topical meeting.

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