q
Workshop of European Group on Ultrarelativistic Heavy Ion Physics
from STAR to ALICE
Close velocity Correlations
Jan Pluta, Warsaw University of Technology
JINR, Dubna9-14. 03. 2006
The starting pointThe starting point
Podgorecki, Kopylov, SmorodinskiDubna, 1974
Weekly meeting of propane bubble chamber group.
1981Lednicky and Lyuboshitzsolved the problem of final state interaction
1972 - 4Kopylov and Podgoretskysettled the basics of correlation femtoscopy:•correlation function,•mixing technique,•role of space-time charakterist...
1975 ...Grishin, propane bubble chamber group and others in Dubna - measured the two-particle correlations
qout
qside
qlong
Rsi
de
R long
Rout
x1
x2
12 ppq
p1
p2
q
12 pp2
1k
Two-particle interferometry: p-space separation space-time separation
• HBT: Quantum interference between identical particles
pairsevent mixed
pairsevent real
)(P)(P
),(P),(
21
2121
pp
ppppC
2long
2long
2side
2side
2out
2out)(1),(
RqRqRqekkqC
q (GeV/c)q (GeV/c)
C (
q)
C (
q)
11
22R
1~
– Final-state effects (Coulomb, strong) also can cause correlations, need to be accounted for
Gaussian model (3-d):
The basic notions
HBT at RHIC...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
RHIC/AGS/SPS Systematics<kT>≈ 400 MeV (RHIC) <kT>≈ 390 MeV (SPS)
Lisa
, P
ratt
, S
oltz
, W
iede
man
n, n
ucl-e
x/05
0501
4
STAR DATASTAR DATA (pp,dAu,CuCu,AuAu@62GeV - prelim.)
Pion HBT radii from different systems and at different energies
scale with (dNch/dη)1/3
Z.Chajęcki, QM’2005
System expansion: System expansion: Initial vs Final Initial vs Final SizeSize
Proton initial size = 0.89 fm from e-scattering
Smooth expansion of the system from p+p to Au+Au
AuAu: system expands
pp (dAu): no or less expansion
Collisions at 200GeV only
Transverse mass dependenceTransverse mass dependence in in AuAu++AuAu
In Au+Au pT (mT) dependence attributed to collective expansion of
the source
0.3 0.30.4 0.40.5 0.50.2 0.2 0.6
STAR, Au+Au@200GeV, PRC 71 (2005) 044906
.2
Calc. with Blast-Wave -Retiere, Lisa, PRC 70 (2004)
044907
0.
0.
0.
Consistency check on flow – Consistency check on flow – kaonskaons
Hania Gos, Kromeriz’05
More confirmationMore confirmation
STAR preliminary
Surprising („puzzling”) scalingSurprising („puzzling”) scaling
All pT(mT) dependences of
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
Ratio of (AuAu, CuCu, dAu) HBT radii by pp
Hania Gos, Kromeriz’05
Nonidentical particle correlations – the asymmetry analysis
k*
1
Catching up•Effective interaction time larger•Stronger correlation
Moving away•Effective Interaction time smaller•Weaker correlation
“Double” ratio•Sensitive to the space-time asymmetry in the emission process
R.Lednicky, V. L.Lyuboshitz,B.Erazmus, D.Nouais,Phys.Lett. B373 (1996) 30.
C-
C+
C+C-
Kinematics selectionalong some directione.g. kOut, kSide, cos(v,k)
Heavier particlefaster
Lighter particlefaster
Adam Kisiel,Fabrice Retiere
Pion-Kaon at 200 AGeV
• Good agreement for same-charge combinations
• Clear emission asymmetry signal
Out double ratio
Side double ratio
Sigma: 17.3 ± 0.8 fm
Mean: -7.0 ± 1.2 fm
STARpreliminary
+ 0.9 syst.- 1.6 syst.
+ 6.1 syst.- 4.0 syst.
kaon faster pion faster
STARpreliminary
Λ peaks
Mean: -7.4 ± 0.9 fm
Sigma: 15.1 ± 0.4 fm
Pion-Proton 130 AGeV• Good agreement
for identical and opposite charge combinations
• We observe Lambda peaks at k*~decay momentum of Λ
Out double ratio
Side double ratio
+ 1.0 syst.- 1.5 syst.
- 3.4 syst.+ 1.9 syst.
Fit assumes source is a gaussian in r*out
proton faster pion faster
Hania Gos, Kromeriz’05
Origins of asymmetry
• 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 = 16.1kaon average = 14.8time shift = 1.3
pion pion emissionemissiontimestimes
kaon kaon emissionemissiontimestimes
primordialprimordial
allall
allall
primordialprimordial
THERMINATORcalculation
Adam Kisiel, Kromeriz’05
Space asymmetry from flow
• 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.
pion pion emissionemissionpointspoints
kaon kaon emissionemissionpointspoints
protonproton emissionemissionpointspoints
outoutsideside
THERMINATOR calculation
Fourier coefficients of HBT() oscillations
Rx
Ry
initi
al =
final
STAR Collaboration, nucl-ex/0312009
• 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
Short expansion time plays dominant role in out-of-plane freeze-out source shapes
eccentricity
Time
2x
2y
2x
2y
RR
RR
Dmitri Peresounko Direct photon interferometry
PHENIX; d+Au collisions at √sNN=200 GeV
ImagingTechniqueImagingTechnique
Technique Devised by:
D. Brown, P. Danielewicz,PLB 398:252 (1997). PRC 57:2474 (1998).
Inversion of Linear integral equation to obtain source function
20( ) 1 ) (,4 ( )C K q r S rq drr
Source Source functionfunction
(Distribution of pair separations)
Encodes FSI
CorrelationCorrelationfunctionfunction
Inversion of this integral equation== Source Function
Emitting source
1D Koonin Pratt Eqn.
Paul Chung, Stony Brook
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.
D Model B
Model A
Model H
Model G
Model E
Model F
Model C
T.Csorgo, Kromeriz’05
Rewiew of Bose-Einstein/HBT Correlationsin high energy heavy ion physics
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
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
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 modelBorysova, Sinyukov, Akkelin, Erazmus, Karpenko
-> More restrictive tests are needed: spectra, v2, HBT, dn/dy
T.Csorgo, Kromeriz’05
Successfull models at RHIC (1): Blastwave
F. Retiere, nucl-ex/0405024; F. Retiere and M. A. Lisa, nucl-th/0312024
Spectra
v2
HBT
T=106 ± 1 MeV
<InPlane> = 0.571 ± 0.004 c
<OutOfPlane> = 0.540 ± 0.004 c
RInPlane = 11.1 ± 0.2 fm
ROutOfPlane = 12.1 ± 0.2 fm
Life time () = 8.4 ± 0.2 fm/c
Emission duration = 1.9 ± 0.2 fm/c
2/dof = 120 / 86
(Errors are statistical only, CL = 0.91 %)
Neglect of resonances
Successfull model (2): Cracow model
nucl-th/0212053
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
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=1680001/3=20
Rexpected < 10fm
Pion freezeout times are about twice as long at LHC compared to RHIC
Tom Humanic, Kromeriz’05
Pion freezeout time and z-position for LHCform 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
Two-pion correlation function for LHCform rescattering calculations
Transverse radius parameters for LHC vs. RHIC
Transverse radius parameters are somewhat larger and show a strongerpT dependence for LHC compared with RHIC
RLong and parameters for LHC vs. RHIC
RLong for LHC is almost twice as large as for RHIC reflectinglonger freezeout times;
behaves about the same at LHC and RHIC
Current status of momentum correlation analysis
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
Results of PPR preparation; Chapter 6.3 Momentum Correlations
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
Two Particle Resolutions
Resolution (r.m.s) [MeV]
Qinv Qout Qside Qlong
PDC04 TPPDC0
4 TP PDC04 TP PDC04 TP
+ 0.9 1.3 3.4 3.8 0.4 0.4 1 0.8
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
- 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
p x x 6.4 8.3 1.9 1.0 2.6 3.2
Almost the same results after ten years of work – very well ( ! ) :reasonable first estimation, and very good complete reconstruction.
Compare the results presented in „Technical Proposal” (TP, in 1995)and obtained from PDC04 (in 2005)
Piotr Skowroński
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 waitingfor the first event of ALICE
Two-particle kinematics
LCMS: (P1+P2)z=0
Getting quantitative -Getting quantitative -What can be probed through fitting?What can be probed through fitting?
Source ofparticle 1
Source ofparticle 2
Boost to pair rest frame
When fitting “double-ratios” two independent variables are accessible:- Mean shift (<r*>) or μ- Sigma (r*)
r* =pairr–pairtr* separation in pair rest frameFunction of pair(pair)
Separation between source 1 and 2 in pair rest frame
r
r [fm] r* [fm]
Two important events;sources of informationand discussion forum:
Quark Matter Conferenceand
satellite topical meeting.