Workshop on Particle Correlations and Fluctuations
The University of Tokyo, Hongo, Japan, September 22, 2011
Oak Ridge National Laboratory
Akitomo Enokizono
9/22/2011
A. Enokizono - WPCF2011
Hadron emission source
functions measured by
PHENIX
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A. Enokizono - WPCF2011
• Physics motivation
• Imaging procedure
• 1D and 3D source functions for charged
pion
• 1D source function for charged kaon
• Experimental systematic uncertainties
• Theoretical descriptions
• Summary
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Outline
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Many reasons not to be a simple
Gaussian
Core
Anomalou
diffusion
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Strong FSI
Normal
diffusion
“Core-Halo” model
p-p correlation function
Coulomb
BEC
Lavy type distribution
Traditional HBT analyses assume the Gaussian source, but no reason
for the emission source to be Gaussian, and more reasonable to expect
the source is a non-Gaussian shape in relativistic heavy-ion collisions
due to resonance decay, rescattering effect, time-dependent expansion
etc…
A. Enokizono - WPCF2011
halo
M. Csanád, T. Csörgő and M. Nagy
hep-hp/0702032
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Imaging correlation function
RPobs (q)  CPobs (q)  1   dr K (q, r) SP (r)
A. Enokizono - WPCF2011
D.A. Brown and P. Danielewicz, Phys. Rev. C 64, 014902 (2001)
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K (q, r)   q (r)  1 is kernel which can be calculated from BEC
and known final state interactions of pairs.
S P (r) is source function which represents the emission
probability of pairs at r in the pair CM frame.
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Optimization (parameters)
Restore
Image
A. Enokizono - WPCF2011
qscale = /2Δr
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rmax : Maximum r
(minimum q) to be imaged.
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1D source for charged pions
A. Enokizono - WPCF2011
9/22/2011
PHENIX Au+Au 200GeV
Phys. Rev. Lett. 98, 132301 (2007)
• The imaged source function deviate from the 3D angle
averaged Gaussian source function at > 15-20 fm.
• Resonance (omega) effect?, Kinetic effect?
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Centrality and momentum
dependence of non-Gaussian
• Long components (Rlr)
depend on both kT and
centrality.
• Not consistent with a
naïve assumption of
omega resonance
contribution.
A. Enokizono - WPCF2011
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PHENIX Au+Au 200GeV
Phys. Rev. Lett. 98, 132301 (2007)
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Theoretical explanation (1)
It is hard to figure out the
origin of non-Gaussian
structure just by looking at 1-D
space.
A. Enokizono - WPCF2011
Each component (e.g. life time,
omega, kinetics. etc) seems to
have different magnitude of
contribution in the 3-D space.
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D.A. Brown, R. Soltz, J. Newby, A. Kisiel
Phys. Rev. C 76, 044906 (2007)
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Pion 3D source function
Sidewards
Longitudinal
• Charged pion 3D S(r) is
measured for the central
Au+Au collision at
200GeV and compared
with blast-wave model.
• A model calculation with
resonance decay + a finite
emission duration agrees
with the experimental
result.
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PHENIX Au+Au 200GeV Phys. Rev. Lett.
100, 232301 (2008)
A. Enokizono - WPCF2011
Outwards
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1D source for charged kaons
A. Enokizono - WPCF2011
9/22/2011
PHENIX Au+Au 200GeV Phys. Rev. Lett. 103, 142301 (2009)
• The result is suggesting non-Gaussian structure in kaon
emission function also.
• Experimental systematic errors are big…
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Experimental Uncertainties (1)
• Two track separation capability
• Significant at low-q (large r) region
• Normalization factor (N)
• C2 = N*A/B is obtained from 3D Gaussian (core-halo) fit.
• Can avoid the uncertainty by imaging directly raw distributions
(A. Kisiel & D.A Brown, Phys. Rev. C 80, 064911 (2009))
A. Enokizono - WPCF2011
• Pion contamination into Kaon data is more significant
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• PID (e.g pion/kaon separation)
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Experimental Uncertainties (2)
Num. of Pair
Central AuAu (~0.7mm), p+p (~2-3cm)
QSignal (q)
Q Background (q)
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Z vertex resolution: Only background
pairs are are affected by finite Zvertex.
resolution for mixed event, and enchance
pair in small-q.
Smeared/Unsmeard
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Momentum resolution: Real pair and
background pair q distributions are
smeared and enhance pairs in small-q.
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Theoretical explanation (2)
A. Enokizono - WPCF2011
9/22/2011
M. Csanád, T. Csörgő and M. Nagy, hep-hp/0702032
The tail by hadronic rescattering
reproduce the experimental nonGaussian structure. (the CoreCore rescattering creates a
significant non-Gaussian part)
The time dependent mean free
path naturally creates nonGaussian tails which depends on
PID (largest for kaons - that have
the smallest cross sections)
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Theoretical explanation (3)
T. Hirano, WPCF2010
Pion
Without hadronic
scattering and decay
With hadronic
scattering and decay
Kaon
Kaon
Without hadronic
scattering and decay
With hadronic
scattering and decay
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Pion
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• Non-Gaussian tails are observed for both pions and
kaons which still has a large experimental uncertainty
• Non-Gaussian tail is not simply explained by omega resonance
decay only.
• Data are reasonably reproduced by hydro models with
resonance decay + rescattering
• Need to be careful about the experimental systematic
errors which is most significant at small q, i.e large r of
the S(r).
A. Enokizono - WPCF2011
• PHENIX has measured 1D source function for charged
pions, kasons and 3D source function for charged pions
in Au+Au 200GeV
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Summary
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