1. Measurement of the branching ratio of the K +     decay Update E. De Lucia, R. Versaci on behalf of the charged kaon group

2. Home works (Hausaufgabe) 1.FILFO correction 2.T3 FILTER correction 3.Efficiency checks 4.Time stability  5.Trigger with not overlapping sectors 

3. FILFO correction C FILFO = 1.00006  0.00032 (DATA) C FILFO = 0.99967  0.00015 (MC) Using the same set of runs for DATA and MC : In agreement within the errors  BR FILFO = 3x10 -4 BR(K  (  ))  BR x C FILFO

4. T3FILTER correction Using the whole DATA sample: BR(K  (  ))  BR x C T3 C T3 = 0.9995  0.0003  BR T3FILTER negligible O(10 -6 )

5. Efficiency evaluation On the sample selected using ECAL we look for a signal event ( i.e. K +     reconstructed in the DC FV) using the same event selection used for the signal sample =

6. Efficiency checks (I) Remember memo #3x10 2 The systematic uncertainties on the efficiency are: 1) Low energy cut (LEC)  BR = 5 x 10 -4 (from 10 to 40 MeV) 2) High energy cut (HEC)  BR = 2 x 10 -4 (from 70 to 90 MeV) standard cuts: LEC = 20 MeV HEC = 80 MeV pollution of the EMC sample  1.2% p*(MeV/c) Calorimeter sample only true K  True K 

7. Efficiency checks (II): pollution/compensation p*(MeV/c) LEC = 40 MeV HEC = 90 MeV 76% generated True K  (  ) pollution  3 % Calorimeter sample only true K  True K  LEC = 10 MeV HEC = 90 MeV 25% generated True K  (  ) pollution  0.7 %

8. Efficiency checks (III) Changing the cuts for the selection of the EMC sample we observe the following maximal variations: DATA efficiency  0 0.3074 (2)  0.3169 (3)   0  3% Pollution in EMC sample 0.7 %  3 % Correction (  CORR ) 0.98008  1.0085   CORR  3% For each EMC sample: 1.evaluate the MC corrections  CORR 2.apply  CORR to the efficiency  0 measured on EMC DATA sample  =  0 x  CORR Then the initial  0  3% becomes   O(10 -4 )   BR  5 x 10 -4 Changing EMC sample : Pollution and compensation have different behaviours!!!! Pollution and compensation have different behaviours !!!!

9. Efficiency checks (IV): Double ratio MC/Data The double ratio stability is related to our sensitivity to changes of the pollution/compensation effects N.B. set1 and set2 applied on independent DATA samples set1 : LEC = 20 MeV HEC = 80 MeV set2 : LEC = 20 MeV HEC = 85 MeV  2 = 90.33/85 A0 = 1.007  0.008

10. Efficiency checks (IV): Double ratio MC/Data The double ratio stability is related to our sensitivity to changes of the pollution/compensation effects N.B. set1 and set2 applied on independent DATA samples set1 : LEC = 20 MeV HEC = 80 MeV set2 : LEC = 25 MeV HEC = 80 MeV  2 = 85.43/85 A0 = 0.9011  0.007

11. Checking various distributions for the kaon tof (ns) KINE Calorimeter sample True K 

12. Checking various distributions for the kaon p K (MeV/c) KINE REC Calorimeter sample True K 

13. Checking various distributions for the decay vtx Rxyz (cm) Rxy (cm) KINE Kaon interacting with the inner DC wall Kaon interacting with the inner DC wall Calorimeter sample True K 

14. Checking various distributions for the secondary p LAB (MeV/c) KINE p LAB (MeV/c) KINE REC Kaon stopped in the inner DC wall, Decay at rest then Plab = 236 MeV Kaon stopped in the inner DC wall, Decay at rest then Plab = 236 MeV Calorimeter sample True K 

15. Checking various distributions for the secondary p LAB (MeV/c) MC-Data comparison DATA MC Kaon stopped in the inner DC wall, Decay at rest then Plab = 236 MeV

16. Checking various distributions for the secondary cos  REC KINE cos  Calorimeter sample True K 

17. Checking various distributions for the secondary p T (MeV/c) L(cm) REC Calorimeter sample True K 

18. The “missed” time stability plot

19. BR K +     = 0.6366  0.0009 (stat.)  0.0012 (syst.) PDG fit = 0.6343  Chiang = 0.6324  Results

20. V us = 0.2223 (25) Results BR K +     = 0.6366  0.0009 (stat.)  0.0012 (syst.) f K /f  =1.210±0.014 (MILC Coll. hep-lat/0407028) Following the method from Marciano hep-ph/0406324 : Vud=0.9740±0.0005 (superallowed  -decays)