measurement of the absolute BR(K  +  -  + ) : an update Patrizia de Simone KLOE Kaon meeting – 21 May 2009

signal selection (I) K tag ,,,,   K sig path triggering  or  0 tag on one side the virtual path of the signal K is given by the tag K track backward extrapolated to the I.P. before the inner wall of the DC in the signal hemisphere we require two reconstructed tracks making a vertex along the K path before the inner wall of the DC missing mass spectrum we look for the signal in the missing mass spectrum

signal selection (II) recovery procedure small changes in the recovery procedure of the K e2 selection selection efficiency require two reconstructed tracks in the DC  the selection efficiency should be given by dvt < 3. cm distance between the extrapolated tracks and the K path dvt < 3. cm momentum of the extrapolated tracks in the K rest frame p* < 190. MeV Fiducial Volume0. <  vtx < 25 cm Fiducial Volume : 0. <  vtx < 25 cm | z vtx | < 20 cm | z vtx | < 20 cm selection efficiency selection efficiency measured on MC corrected with  single trk (data)  single trk (MC) whole 2002 Data Sample no no charge requirements for the selected tracks p (selected tracks) < 200. MeV/c  sel =  single trk x  single trk x  cuts  geo ≈ 26 %

dataMC missing mass 2 (Mev 2 ) the selected sample tag triggering  mass window  < missing mass 2 (MeV 2 ) dataMC missing mass 2 (Mev 2 ) tag triggering  

the signal to evaluate the background contribution we fit the Missing Mass spectrum using the MC signal and background shapes K + tag triggering  ¼ of the 2002 data sample : ¼ of the 2002 data sample : signal conting statistical error ≈ 0.4 % Mass miss 2 bin = 2000 MeV 2 kumacs and help of Erika signal counting window  < M miss 2 MeV 2 varying the fit range < M miss 2 < MeV 2 M miss 2 > 0.0 MeV 2 the signal counting is stable within 0.2%

K ±   ±  0  0 control sample stepping along the K ± sig path build a  2 –like  2 –like variable based on 4 neutral clusters on time on time with the K ± sig ToF  2 < 30 select the 2 best  pairing and keep the event if (InvMass(  ) 1 – M  0 )/  M < 4..and. (InvMass(  ) 2 –M  0 )/  M < 4.  M ≈ 18 MeV ) p  ± = pK ± – p  0 – p  0 and finally … to measure the single track reconstruction efficiency

M miss 2 (MeV)  p  (MeV) M miss 2 < 400 MeV 2 K ±   ±  0  0 control sample: p  ± kine resolution  p  (MeV) M miss 2 < 400 MeV 2  p  ≈ 14 MeV X  0  0 vertices found in the FV (0. <  vtx < 25. ) cm (0. <  vtx < 25. ) cm |z vtx | < 20. cm |z vtx | < 20. cm  62% in  62% of the cases purity  99% the purity of the sample is  99%

resolutions: neutral VTX vs DC reconstructed quantities bin p  = 30 MeV  p  (MeV)  p  ≈ 14 MeV dataMC  vtx  (cm)  vtx ≈ 2.2 cm dataMC     ≈ 10 dataMC bin  vtx = 5 cm bin   = 30

distributions of the DC reconstructed quantities dataMC  bin   1 bin   2 bin   3   (cm) dataMC bin  vtx 1 bin  vtx 2 definition of the correction efficiency tables  bin   = 30 dataMC p  (MeV)

bin   2 bin  vtx 2 bin  vtx 1 bin   1 bin   3 bin  vtx 2 bin   2 bin   1 p  (MeV) correction efficiency tables p  (MeV) data(K   ±     ) sel  single trk MC(K   ±     ) sel  single trk K + : tag triggering  K + : tag triggering  

signal selection efficiency signal signal ≡ extrapolated tracks.ge.2 dvt 1 dvt 2 (dvt 1 < 3.).and. (dvt 2 < 3.) cm p* 1 p* 2 (p* 1 < 190.).and.(p* 2 < 190.) MeV mass window p  (MeV)  selection kine = signal N(K -> 3  ) in FV ifsignal N(K -> 3  ) in FV  sel  K + red K - blue  sel  vtx (cm)  kine MC folded with  single trk (DATA)  single trk (MC) K + : tag triggering  ± K + : tag triggering   ± 0.001

tag bias correction estimated from the 2002 MC kpm04 tag triggering  tag triggering   tag  tag   K+K+ K-K- ( ± 0.074)% ( ± 0.074)% ( ± 0.114)% ( ± 0.115)% ( ± 0.117)% ( ± 0.117)% ( ± 0.165)% ( ± 0.166)%

filfo correction tag triggering  tag triggering   K+K+ K-K ± ± ± ±

T3 filter correction tag triggering  tag triggering   K+K+ K-K- using the whole DATA sample ± ± ± ±

why ? PDG fit ‘06 PDG fit ‘06 BR(K       ) = (5,59 ± 0.03)%  BR/BR = 5,4x10 -3 CHIANG ’72 CHIANG ’72 (2330 evts) BR(K       ) = (5,56 ± 0.20)%  BR/BR = 3,6x10 -2 no radiative correction this BR enters in the CUSP analysis to extract the  phase shifts done by NA48 the complete set of new measurements of the absolute BRs of the dominant K ± decays to have the complete set of new measurements of the absolute BRs of the dominant K ± decays the 6 absolute BRs all together moreover we will measure the 6 absolute BRs all together with the whole KLOE data set, this will allow us to obtain “easily” the correlations between the K ± BRs measurements (FlaviaNet fit constrained by  BR = 1)