4/27/101 Test of KFParticle with K 0 s J. Bouchet

4/27/102 outline Test KFParticle with a easier decay particle ctau(K0)~ 2cm TCFIT was already tested on K0s and Lambda and shown good results : – ambda.pdfhttp://drupal.star.bnl.gov/STAR/system/files/update_L ambda.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)

4/27/103 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

4/27/104 #of events Nothing unusual # of events after vertex position Z and vertex resolution position cut is ~80 kEvents

4/27/105 KFDecayLength Large background for |KFDecayLength|< 2cm Similar to what gives the standard V0 finder

4/27/106 Inv mass No cut here No inv. Mass is seen before any topological cuts

4/27/107 Inv Mass |n  |<2 KFDecay>0 |n  |<2 KFDecay>1 |n  |<2 KFDecay>1.5

4/27/108 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

4/27/109 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

4/27/1010 Applying a cut on  L No cut  L >40

4/27/1011 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)