1. Charged kaon lifetime F. Ambrosino, P. Massarotti. Paolo Massarotti Kloe meeting 10 march 2005

2. Measure ot  : length Paolo Massarotti Kloe meeting 10 march 2005

3. Signal and background Paolo Massarotti Kloe meeting 10 march 2005  good vertex (65%)  wrong vertex (35%)

4. Background analysis Four families:  good vertex (~ 67%)  kaon hits associated to daughter track (~ 21%)  daughter hits associated to kaon track (~ 7%)  kaon broken track(~ 5%) Daughter P* with kaon mass hypothesis Cut at 100 MeV Paolo Massarotti Kloe meeting 10 march 2005

5. Background analysis: vertex quality Paolo Massarotti Kloe meeting 10 march 2005 Cut at Vertex quality = 1

6. Background analysis:    vertex Paolo Massarotti Kloe meeting 10 march 2005 Cut at  2 vertex < 3

7. Background analysis: cosine kaon daughter Paolo Massarotti Kloe meeting 10 march 2005 After the cuts…

8. Definition of Samples: Paolo Massarotti Kloe meeting 10 march 2005 Cut at 100 MeV on boost & Vertex quality = 1 &  2 vertex < 3 with 81% of efficiency Cut at 100 MeV on boost & Vertex quality = 1 &  2 vertex < 3 & |cosine| < 0.8 with 65% of efficiency

9. Efficiency: first cut Paolo Massarotti Kloe general meeting 28 october 2004

10. Efficiency: second cut Paolo Massarotti Kloe meeting 10 march 2005

11. Fit stability for the first sample: bin  ±  N bin  (ns)

12. Paolo Massarotti Kloe meeting 10 march 2005 Fit stability for the first sample: range  ±  Range (ns)  (ns)

13. Paolo Massarotti Kloe meeting 10 march 2005 Fit stability for the second sample: bin  ±  N bin  (ns)

14. Paolo Massarotti Kloe meeting 10 march 2005 Fit stability for the first sample: range  ±  Range (ns)  (ns)

15.  Reco  –  true Paolo Massarotti Kloe meeting 10 march 2005 The problem of resolution  (ns)

16. Background: Data and MonteCarlo Paolo Massarotti Kloe meeting 10 march 2005 Before cuts MC : 67%good, 33%bck Data: 65%good, 35%bck After the first cut MC : 73%good, 27%bck Data: 70%good, 30%bck

17. Conclusions Paolo Massarotti Kloe meeting 10 march 2005 We have studied background variation as function of different cuts We have analyzed the stability of the fit as function of the bin width and of the fit range We have to fit using a function given by the convolution of an exponential and a resolution function