1. data vs MC … issues of the K +- group 1.Accidentals … contribution from Erika & Roberto 2.DC background

2. Efficiency evaluation for BR(K  (  )) Double K  events selection 1)isolate triggering cluster of the muon tag 1 cluster 2)only 1 cluster with E CLU > 20 MeV and anything with E CLU < 20 MeV 1 cluster 3) further cuts on 1 cluster 90 < E CLU < 320 MeV and no clusters with 20 < E CLU < 90 MeV To avoid correlation with the DC driven sample selection, we select the efficiency sample using mainly EMC information E CLU MeV Low energy cut Medium energy cut High energy cut

3. The new look of the MC E CLU MeV Shift = -1.8 MeV Smear = To reject accidental clusters cut in E CLU vs R T plane ((E+R T /5).ge.110).or. (R T.gt.197)

4. … concerning the K  trk efficiency … K +  X  0 cm red  MC blue  data green  MC truth global efficiency vs decay lenght K ±  X  0 cm red  MC blue  data green  MC truth (vtx + sec trk) efficiency vs decay lenght

5. maybe the simulation of the background … … is not accurate for the charged kaon events.. ?? select double tagged K   events, and look at the distribution of the ratio : N hits (associated to a track by the fit) N hits (total # in the DC) data MC .. charged Kaon tracks MAINLY affected by spurios background hits ? … to confirm such a hypotesis look at the layer occupancy of the NOT associated hits

6. layer occupancy of the NOT associated hits data MC double tagged K   events 3X3 cm 2 2X2 cm 2 data MC Bhabha events 3X3 cm 2 2X2 cm 2

7. ideas to add the background … track layers associated hit not associated hit data MC.. sampling the distribution of..  r = distance between the associated hit and the bck hits per layer