Paricle Correlations and Femtoscopy at RHIC

1
Selected results on strong- and coulomb-induced
correlations from STAR experiment
Michal umbera Nuclear Physics Institute ASCR
Re/Prague
WPCF 2006, São Paulo, 9th 11th September, 2006
2
Outline

• Space-time structure of multi-strange baryon
  source via ?-? correlations
• (Petr Chaloupka)
• Motivation
• Update on previous analysis
• Comparison with predictions from UrQMD(?)
• Identical pion correlations
• (Michal Bysterský)
• Motivation/summary of previous analysis
• 1D imaging analysis of AuAu and CuCu STAR data
  on identical pions

3
RHIC femtoscopy matrix Mikes table (M. Lisa,
ISMD, Kromerí 2005)
P. Chaloupka, J.Phys. Gxx
,2006, in print Nucl.Phys.A774603-606,2006
AIP Conf.Proc.828610-614,2006
Nucl.Phys.A749283-286,2005
? ? prelim or final result available
4
Why p-X correlations?

• Why is X elliptic flow comparable to other
  hadrons? Is that all suggesting early partonic
  collectivity?
• X (as well as other multi strange baryons) may
  have thermal freeze-out behaviour differing from
  the other hadrons e.g. early decoupling?
• What is the production mechanism of X (1530)
  resonance?

5
X -production _at_RHIC elliptic flow
AuAu vsNN200 GeV

Sevil Salur QM05 Nucl.Phys.A774657-660,2006
6
X -production _at_RHIC radial flow
Most Central Collisions

• Temperature Tfo is higher for baryons with
  higher strange quark content for Blast-wave fits.
• Spectral shapes are different.

Temperature Tfo (GeV)

• p,K, p lt?Tgt at 200 GeV gt 62 GeV Tfo at
  200 GeV 62 GeV
• X, W lt?Tgt at 200 GeV 62 GeV Tfo at
  200 GeV gt62 GeV

Sevil Salur _at_ QM05 Nucl.Phys.A774657-660,2006
7
What the hydro tells us about multistrange
baryons at RHIC
Heavy hadrons, which are particularly sensitive
to radial flow effects, require the additional
collective push created by resonant
(quasi)elastic interactions during the fairly
long-lived hadronic rescattering stage between
Tcr and Td
) e.g. ??? ? ???
U. Heinz, J. Phys. G31,S717, 2005
8
Influence of the hadronic phase succeeding the QGP
C. Nonaka, S. Bass nucl-th/0607018
HydroUrQMD
9
Resonant states in p-X system
Life time fm/c ? (1020) 47
L(1520) 13 S(1385) 5
K(892) 4
? (1530) 22
10
Recent development (since WPCF05)

• Re-run of ?? HBT analyses in order to extract ?
  in low kT bins 125 MeV/c ? pT ? 1GeV/c)
• Increased acceptance for pions from ???? 0.5 to
  ???? 0.8
• 2D-binning 10cm wide vertex bins ? multiplicity
  bins replaced by 3D-binning
• 10cm wide vertex bins ? multiplicity bins ?
• 5 event plane bins

11
(Re)analyzed data
200GeV AuAu, run IV data 41.4M events
out of which 26.4M are from central trigger
sample
12
dE/dx electron cut ?-? purity
2 ? cut around electron band
dE/dx eV/cm
dE/dx eV/cm
13
STAR preliminary
14
STAR preliminary
15
Conclusion 1 dE/dx electron cut influnces ? but
not the emission radii Rout, Rside or Rlong
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AuAu _at_ 200GeV, centrality 0-5
STAR preliminary
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AuAu _at_ 200GeV, centrality 0-5
STAR preliminary
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AuAu _at_ 200GeV, centrality 0-5
STAR preliminary
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AuAu _at_ 200GeV, centrality 0-5
STAR preliminary
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Conclusion 2 Using two different pion purities
we get to the same final C(k) ? the systematic
error from pion purity is under control
21
From m?? to C(k)
?(1530)
STAR preliminary
200 GeV AuAu 40-80
22

Reaction plane binning improvement
62 GeV AuAu
Without reaction plane binning
With reaction plane binning
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p-X correlations in AuAu

• Coulomb and strong ( X1530 ) final state
  interaction effects present.
• Centrality dependence observed, particularly
  strong in the X region

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p-X systematics the summary

• Strong
• system dependence

• No significant energy dependence

25
Petr Chaloupka WPCF05
26
Measuring production offset by kinematic selection

• If space-time ordering, select between two
  configurations
• A) Both particles are moving away from each other
• B) One particle is catching up
• Final state interactions yield different
  correlations for these two configurations

27
Spherical harmonics decomposition of
non-identical particle correlations
Z. Chajecki , T.D. Gutierrez , M.A. Lisa and M.
López-Noriega, nucl-ex/0505009
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Spherical harmonics decomposition of
non-identical particle correlations

• Different Alm correspond to different
  symmetries of the source
• A00 - monopole ? size
• A11 - dipole ? shift in out-direction
• A2m quadrupole ? shape
• .....

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Petr Chaloupka WPCF05
30
200GeV AuAu central

• A11 ? 0 - shift in the average emission point
  between p and X could be clearly seen showing
  that pion is catching up with the X in
  qualitative agreement with transversally
  expanding source.

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Summary on p-X correlations

• High statistics measurements of p-X correlations
  were presented.
• Coulomb and strong FSI were observed.
• Very good sensitivity to source size in X peak
  was found. More theoretical is input needed.
• Spherical harmonics representation of data allows
  to observe that pion is catching up with the X
  in qualitative agreement with transversally
  expanding source.
• Prospect for the same type measurement after
  STAR detector upgrades and also with ALICE at LHC
  seems good!!

32
2. Identical pion correlations
33
Fabrice Retière WPCF05
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Fabrice Retière WPCF05
35
(No Transcript)
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Michal Bysterský WPCF05
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Imaging a short introduction
N.B. prime means in the pair CMS frame
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Inverting expression for angle averaged
correlation function

• Task of imaging is to determine the source S(r )
  from C(q) by inverting the Koonin-Pratt integral
  equation

D. A. Brown and P. Danielewicz, Phys. Let
B398(1997)252 Phys. Rev C, 57 (1998) 2474
Code for inverting the angle averaged correlation
function can be downloaded from
http//www-phys.llnl.gov/Research/source_imaging/H
BTprogs.html
39
S.S. Adler et al., (Phenix coll.)
ArXivnucl-ex/0605032
The source parameters extracted from these
functions at low kT , give first indications of a
long tail for the pion emission source. The
source extension cannot be explained solely by
simple kinematic considerations. The possible
role of a halo of secondary pions from resonance
emissions is explored.
40
Testing the reproducibility 1/2
40-80
10-40
0-10
RQMD, assuming isotropic Gaussian source, R5fm,
??0
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Testing the reproducibility 2/2

• Reproduction of the input parameters is not very
  good ?RG/RG ? 5, ??/? ? 25(!) (may be due to
  finite statistics, fit parameters effect, code
  itself?)
• The shape of the distribution is reproduced
  rather well

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The same data cuts as in the previus pion purity
analysis were used except for the dE/dx
electron cut
N.B. All experimental data processed with single
set of input parameters Ndata28,Nmodel12,Neqcon
5
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Comparing STAR data to PHENIX
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Two simple source parametrizations
N.B. Have not tried spheroid fit, yet
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AuAu 3 centrality bins
40-80
10-40
0-10
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AuAu 3 centrality bins
10-40
40-80
0-10
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AuAu 0-5
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AuAu 0-5
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AuAu 0-5
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AuAu 0-5
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AuAu 0-5
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AuAu 0-5
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AuAu 0-5
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AuAu 0-5
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AuAu 0-5
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AuAu 10-40
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AuAu 10-40
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AuAu 10-40
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AuAu 10-40
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AuAu 10-40
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AuAu 10-40
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AuAu 10-40
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AuAu 10-40
64
AuAu 10-40
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AuAu 40-80
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AuAu 40-80
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AuAu 40-80
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AuAu 40-80
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AuAu 40-80
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AuAu 40-80
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AuAu 40-80
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AuAu 40-80
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AuAu 40-80
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Summary on double gaussian fit
STAR preliminary
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Comparison ? from imagining and from 3D fit to
c.f.
STAR preliminary
1.
The same undershoot like for the RQMD case
0.8
0.6
76
CuCu 3 centrality bins
40-60
10-40
0-10
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CuCu 3 centrality bins
10-40
40-60
0-10
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CuCu 0-10
79
CuCu 0-10
80
CuCu 0-10
81
CuCu 0-10
82
CuCu 10-40
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CuCu 10-40
84
CuCu 10-40
85
CuCu 10-40
86
CuCu 40-60
87
CuCu 40-60
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CuCu 40-60
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CuCu 40-60
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Summary on double gaussian fit
STAR preliminary
91
Summary on identical pion correlations

• Particle source imagining technique was applied
  to correlation functions C(qinv) of identical
  charged pions produced at mid-rapidity in AuAu
  and CuCu collisions at ?sNN200 GeV.
• High statistics of analyzed data allowed us to
  study centrality and kT-dependence of extracted
  emission source functions with useful accuracy
  out to relative pion separations of about 30 fm.
• Source functions can not be described by a single
  Gaussian due to substantially wider shape of the
  relative pion separations distribution.

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The STAR Collaboration
U.S. Labs Argonne, Lawrence Berkeley, and
Brookhaven National Labs U.S. Universities
UC Berkeley, UC Davis, UCLA, Caltech,
Carnegie Mellon, Creighton, Indiana, Kent State,
MIT, MSU, CCNY, Ohio State, Penn State, Purdue,
Rice, Texas AM, UT Austin, Washington, Wayne
State, Valparaiso, Yale Brazil
Universidade de Sao Paolo China IHEP -
Beijing, IPP - Wuhan, USTC, Tsinghua, SINAP, IMP
Lanzhou Croatia Zagreb University Czech
Republic Nuclear Physics
Institute England University of Birmingham
France Institut de Recherches Subatomiques
Strasbourg, SUBATECH - Nantes Germany Max
Planck Institute Munich University of
Frankfurt India Bhubaneswar, Jammu, IIT-Mumbai,
Panjab, Rajasthan, VECC Netherlands NIKHEF/Utrec
ht Poland Warsaw University of
Technology Russia MEPHI Moscow, LPP/LHE
JINR Dubna, IHEP Protvino South
Korea Pusan National University
Switzerland University of Bern