Hadron ID and Event-by-event Fluctuations of the Kaon to Pion

Ratio

D. Kresan,

GSI, Darmstadt

13-th CBM Collaboration Meeting9 – 13 March 2009

GSI, Darmstadt

2009-03-12 D.Kresan CBM Collaboration Meeting, GSI, Darmstadt 2/19

Simulation tools

• CBMROOT trunc version (revision 4448)• STS

– 8 Strips

• TRD– 3x4 Setup– Hit Producer: Angular dependent strip-like smearing

• TOF– Segmented geometry– Hit Producer: double hits– 80ps time resolution

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Track cuts

• Select only primaries• Identification of tracks is done using momentum-

dependent window around the true squared mass

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STS Reconstruction

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TRD Reconstruction

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Global Tracking

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Squared Mass Spectra

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Correctly Reconstructed Tracks

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Squared Mass Resolution

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Kaon pt at midrapidity

purity 90%

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pt – y distributions

purity 90 %

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Dynamical Fluctuations

Measure the particle yields ratio in an event :

K/

Relative width of distribution : = RMS / MEAN

data2 = fin

2 + exp2 + dyn

2

background

Event mixing: no two tracks coming from one real event

mixed

dyn2 = data

2 mixed2

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Results from UrQMD

4 RECO+PID

No large acceptance bias

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Purity Study: K/

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Purity Study: p/

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4

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acc

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RECOpurity 50%

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Conclusion

• Exponential tails in mass spectrum are due to mismatches and TOF double hits

• Investigation of the effect of kaon purity was done for K/ and p/ ratios

• Increase of K/ fluctuations due to limited momentum range

• Agreement between "real" and MC (with p cut) results– no bias due to acceptance, reconstruction and

identification