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Hadron emission source functions measured by PHENIX. Workshop on Particle Correlations and Fluctuations The University of Tokyo, Hongo , Japan, September 22, 2011 Oak Ridge National Laboratory Akitomo Enokizono. Outline. Physics motivation Imaging procedure

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hadron emission source functions measured by phenix

Hadron emission source functions measured by PHENIX

A. Enokizono - WPCF2011

Workshop on Particle Correlations and Fluctuations

The University of Tokyo, Hongo, Japan, September 22, 2011

Oak Ridge National Laboratory

Akitomo Enokizono

outline
Outline
  • Physics motivation
  • Imaging procedure
  • 1D and 3D source functions for charged pion
  • 1D source function for charged kaon
  • Experimental systematic uncertainties
  • Theoretical descriptions
  • Summary

A. Enokizono - WPCF2011

many reasons not to be a simple gaussian

halo

Core

Many reasons not to be a simple Gaussian

p-p correlation function

M. Csanád, T. Csörgő and M. Nagy hep-hp/0702032

Strong FSI

Anomalou

diffusion

Coulomb

BEC

Normal

diffusion

A. Enokizono - WPCF2011

Lavy type distribution

“Core-Halo” model

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, rescatteringeffect, time-dependent expansion etc…

imaging correlation function
Imaging correlation function

is kernel which can be calculated from BEC and known final state interactions of pairs.

is source function which represents the emission probability of pairs at r in the pair CM frame.

D.A. Brown and P. Danielewicz, Phys. Rev. C 64, 014902 (2001)

A. Enokizono - WPCF2011

optimization parameters
Optimization (parameters)

rmax : Maximum r (minimum q) to be imaged.

qscale = /2Δr

Image

Restore

A. Enokizono - WPCF2011

1d source for charged pions
1D source for charged pions

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?

A. Enokizono - WPCF2011

centrality and momentum dependence of non gaussian
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.

PHENIX Au+Au 200GeV

Phys. Rev. Lett. 98, 132301 (2007)

A. Enokizono - WPCF2011

theoretical explanation 1

Each component (e.g. life time, omega, kinetics. etc) seems to have different magnitude of contribution in the 3-D space.

It is hard to figure out the origin of non-Gaussian structure just by looking at 1-D space.

Theoretical explanation (1)

D.A. Brown, R. Soltz, J. Newby, A. Kisiel Phys. Rev. C 76, 044906 (2007)

A. Enokizono - WPCF2011

pion 3d source function
Pion 3D source function

Outwards

PHENIX Au+Au 200GeV Phys. Rev. Lett. 100, 232301 (2008)

  • 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.

Sidewards

A. Enokizono - WPCF2011

Longitudinal

1d source for charged kaons
1D source for charged kaons

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…

A. Enokizono - WPCF2011

experimental uncertainties 1
Experimental Uncertainties (1)
  • Two track separation capability
    • Significant at low-q (large r) region
  • PID (e.g pion/kaon separation)
    • Pion contamination into Kaon data is more significant
  • 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

experimental uncertainties 2
Experimental Uncertainties (2)

Smeared/Unsmeard

Momentum resolution: Real pair and background pair q distributions are smeared and enhance pairs in small-q.

Z vertex resolution:Only background pairs are are affected by finite Zvertex. resolution for mixed event, and enchance pair in small-q.

Central AuAu (~0.7mm), p+p (~2-3cm)

A. Enokizono - WPCF2011

Num. of Pair

theoretical explanation 2
Theoretical explanation (2)

M. Csanád, T. Csörgő and M. Nagy, hep-hp/0702032

A. Enokizono - WPCF2011

The time dependent mean free path naturally creates non-Gaussian tails which depends on PID (largest for kaons - that have the smallest cross sections)

The tailby hadronicrescattering reproduce the experimental non-Gaussian structure. (the Core-Core rescattering creates a significant non-Gaussianpart)

theoretical explanation 3
Theoretical explanation (3)

T. Hirano, WPCF2010

Pion

Pion

Without hadronic

scattering and decay

With hadronic

scattering and decay

A. Enokizono - WPCF2011

Kaon

Kaon

With hadronic

scattering and decay

Without hadronic

scattering and decay

summary
Summary
  • PHENIX has measured 1D source function for charged pions, kasons and 3D source function for charged pions in Au+Au 200GeV
    • 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 rof the S(r).

A. Enokizono - WPCF2011