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Test of KFParticle with K 0 s

Test of KFParticle with K 0 s. J. Bouchet. outline. Test KFParticle with a easier decay particle ctau(K0)~ 2cm TCFIT was already tested on K0s and Lambda and shown good results : http://drupal.star.bnl.gov/STAR/system/files/update_Lambda.pdf What we can know : KFParticle agree with TCFIT

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Test of KFParticle with K 0 s

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  1. Test of KFParticle with K0s J. Bouchet

  2. outline • Test KFParticle with a easier decay particle • ctau(K0)~ 2cm • TCFIT was already tested on K0s and Lambda and shown good results : • http://drupal.star.bnl.gov/STAR/system/files/update_Lambda.pdf • What we can know : • KFParticle agree with TCFIT • Joe has shown that TCFIT works for long decay • Files used : day 110 to 112 from ProductionMinBias (run7)

  3. cuts • static const Double_t pTCut = 0.5; // transverse momentum cut • static const Double_t mKpiMin = 0; // min mass of (Kpi) association • static const Double_t mKpiMax = 1; // max mass of (Kpi) association • static const Double_t DcaCut = 1; // single track DCA to PV • static const Int_t TpcCut = 20; // TPC hits fitted • static const Double_t TrackLengthCut = 40; // min value for dEdxTrackLength • static const Int_t SiCut = 2; // (SVT+SSD) hits fitted • static const Float_t SigmaPionCut = 3; // ndEdx for pion • static const Float_t SigmaKaonCut = 3; // ndEdx for kaon • static const Double_t EtaMin =-1.0; // min track pseudorapidity • static const Double_t EtaMax = 1.0; // max track pseudorapidity • static const Double_t zcut = 5; // zvertex cut • static const Double_t PrimZResCut = 0.02; // zvertex cut • static const Double_t sigmaTCut = 2.0; // ratio single track dca/sigmaDca • static const Double_t ProbKFCut = 0.05; // lower limit for the probability of KF particle • static const Int_t writeHisto = 0; // flag to write histos

  4. #of events • Nothing unusual • # of events after vertex position Z and vertex resolution position cut is ~80 kEvents

  5. KFDecayLength • Large background for |KFDecayLength|< 2cm • Similar to what gives the standard V0 finder

  6. Inv mass • No cut here • No inv. Mass is seen before any topological cuts

  7. Inv Mass |n|<2 |n|<2 KFDecay>0 |n|<2 KFDecay>1 |n|<2 KFDecay>1.5

  8. comments • As for the standard V0 finder, a cut on decay length remove background • For decay>1.5, almost no background and a clear peak appears

  9. Decay length significance L • L is defined as : • Decay length/error of decayLength • No other cuts than the |n |<2 for both pions daughters • positive contributions appear for L >40

  10. Applying a cut on L No cut L >40

  11. Summary - to check • Cut on decay length from KFParticle removes background • Similar to V0Finder and TCFIT • Cut on L seems high : • have to check the error on decay length (if not underestimated) • Could try the lambda decay to check if KFParticle finds a larger decay length according to the one from lambda(c ~ 7 cm)

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