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γ -charge particle correlation analysis. Prithwish Tribedy , Arindam Roy (VECC). Motivation. 1. The charged particles are measured from the FTPC and photons from the PMD at forward rapidity. Correlation between productions of charged and neutral pions have been studied at top RHIC energy.

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charge particle correlation analysis

γ-charge particle correlation analysis

PrithwishTribedy, Arindam Roy



1. The charged particles are measured from the FTPC and photons from the PMD at forward rapidity. Correlation between productions of charged and neutral pions have been studied at top RHIC energy.

2.The energy dependence of the isospin fluctuation of pions in BES would be an interesting study in the context of phase transitions .

issues addressed in the following presentation
Issues addressed in the following presentation :
  • AuAu 200 GeV Run 7- Run 10 comparison
  • PMD – FTPC West correlation
run 10 data
Run 10 data





1 sigma cut applied to remove outlier runs

Checking consistency with Run10 data

Run 10: AuAu200

Prod: P08ic

Stlib: SL10K


Events : 3.5 M

Centrality: ReMultCorr

Bad Runs : Alex-Hiroshi list

+ PMD-FTPC list

|Vz|<5 cm

|vpd(Vz)-TPC(Vz)|<4 cm

All standard cuts of PMD-FTPC

The PMD bad events are removed by putting a cut on cpvfrac (= cpvadc/cpvcluster)

We use cpvfrac >1.8 for our analysis

Some more cleanup

Using #primary vertex cut.

npV=1  better cleanup

Looks clean except for

peripheral events.

Run7-Run10 looks consistent

Some difference may be due to some bad-events in the peripheral collisions.

PMD & FTPC East – FTPC West comparison

Issue 1 : Difference in multiplicity even in same acceptance (Run10 is better )

Run 7



In multiplicity

Run 10

PMD & FTPC East – FTPC West comparison

Issue 2 : Contamination effect makes direct comparison misleading

  • GEANT Simulation shows 30% of the photons might contain different contamination in the same coverage which can’t be completely removed.
  • So some of the photons from PMD include FTPCE tracks. So PMD-FTPCE correlation will be more than PMD-FTPCW.



= α + εγ

and are average measured multiplicities from PMD and FTPC East.

is actual photon multiplicity in the coverage considered, εγis photon detection efficiency.

α Unknown contamination factor.


Correlation of PMD with East and West FTPC : comparison

It can be easily shown that the contamination will affect not only the same side correlation

but also the opposite side correlation in different way.

One can’t get rid of the unknown contamination factor by algebraic manipulation.

Correlation of PMD with East and West FTPC : comparison from Run10 data
  • ΔCorrWest-East
  • = Correlation (FTPCW-PMD)
  • Correlation
  • Depending on the value of unknown contamination factor it is not possible to conclude which side has more correlation.

Run10 comparison:

Run7-Run10 data are consistent, although some cleanup issues still remain with Run10 data.

PMD-FTPCW (away-side) correlation:

-It is hard to make a conclusion by comparing PMD-FTPCW and PMD-FTPCE correlation.

-The difference in correlation between FTPCEast and FTPCWest

depends on the unknown contamination factor, alpha. Higher correlation with FTPCWest would have indicated interesting physics signal where as higher correlation with FTPCEast would indicate dominance of resonance and jets etc.

results for the observable dyn
Results for the observable νdyn

Results for Top energy

(systematic error bars are included)

Energy and centrality dependence of the observable νdyn

νdyn is a measure of dynamical fluctuation, non-zero νdyn dynamical fluctuation

Non-zero νdyn is observed over wide range of centrality and energy.

Observation :


γ-ch fluctuation result is very different from positive-negative

charge fluctuation.



DCC expectation

Observable r_{m,1} shows :

Deviation from Poisson is small, result is consistent with particle production from equilibrated matter. (hydrodynamic evolution).