BR(  ) with     7  Camilla Di Donato INFN Napoli Camilla Di Donato INFN Napoli 20/02/2004

Camilla - Rad. Meeting BR(  ) measurement BR(  ) measured on 2000 data    - 3  : Phys. Lett. B541 (2002)    - 7  km 268 and analysis update with referee suggestions crg       and       ntr       and       BR(  ) and  P evaluation on data; L int =449 pb -1

Camilla - Rad. Meeting BR(  ) measurement Update the old analysis Analysed 449pb -1 from data collection time window = min(5  t,2ns) EMC-MC threshold accidentals in DC input kin.fit: pull cut on cos   <- 0.9 and on E      removed Analysis of background cos    1 with didone Systematic error evaluation completed (excluding VTX)

Camilla - Rad. Meeting Trigger-FILFO-EVCL We check Trigger FILFO and Event Classification Trigger:  MC (crg) = 99.7%;  MC (ntr) = 99.9% On events selected by the analysis we found  MC =100% Ecap East Ecap West Barrel

Camilla - Rad. Meeting Trigger-FILFO-EVCL FILFO-EVCL on triggered events:  MC (crg) = 57.88%;  MC (ntr) = 61.45% We check the efficiency mc value performing the analysis on unbiased sample (1/5 of 2002 data) in order to evaluate a systematics. We find (  MC –  data )/  MC =2%

Camilla - Rad. Meeting Topological selection  MC (crg) = (19.61±0.05)%;  MC (ntr) = (20.56±0.08)% check  (N/  )/(N/  )  z vtx = ±15%±0.4%   = ±1  ±1%  E  = ±2%±0.1%  2 /Ndf= ±1±1% Total ±1.5%

Camilla - Rad. Meeting : L int =449 pb -1 N ob.ev. = 3863±62 From MC study we estimated the expected background: Ks   +  - ; Kl   0  0  0 N bg1 = 64 Ks   0  0 ; Kl   +  -  0 N bg2 = 168 Ks   +  -  ; Kl   0  0  0 N bg1 = 141 N  ’   = N ob.ev. - N bg N  ’  = 3490±62

Camilla - Rad. Meeting N ob.ev. = 3863±62 E  + +E  + (MeV)  2 /Ndf Ks   +  - Kl   0  0  0 Ks   0  0 Kl   +  -  0 Ks   +  -  Kl   0  0  0 Signal

Camilla - Rad. Meeting M  is obtain from the “best” 3  rad Ks   +  - Kl   0  0  0 Ks   0  0 Kl   +  -  0 Ks   +  -  Kl   0  0  0 Signal E  rad (MeV) M  (MeV) Right  rad  80%

Camilla - Rad. Meeting Results N  ’  = 3490±62 N  = L int  (e+e-  )  4% –L int = 449 pb -1  1% –  (e+e-  ) =(3.34  0.01  0.12)  b (Kn177 Simona and Stefano)  4% (due to BR” from PDG’02)  (N/  )/(N/  )  1.5% Filfo-Evcl  2%

Camilla - Rad. Meeting Results BR(  ) = (6.04±0.10±0.36)10 -5    - 3  : Phys. Lett. B541 (2002) BR(  ) = (6.10±0.61±0.43)10 -5 R= BR(  )/BR PDG02 (  )   P (Bramon) Mixing angle evaluation

Camilla - Rad. Meeting Conclusions and Outlooks We look at the full KLOE statistic; BR(  ) measurement almost completed: to be check vtx effect on systematics; Pseudoscalar mixing angle evaluated; A Kloe Memo is in preparation (I need to discuss with Simona and Paolo, my referee)

Camilla - Rad. Meeting Unbiased sample ……… ……………for Filfo-Evcl study 2002: done 29 pb -1 run  11 pb -1 (all runs) run  18 pb -1 (one run each ten) 2001: to be done run datarec V13  11 pb -1 run datarec V14  8 pb -1