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K  two body decays

K  two body decays. Absolute BR measurements BR( K      ) B. Sciascia BR( K   p  p 0 ) E. De Lucia BR( K   p  p 0 )/BR( K      ) M. Martemianov, V. Kulikov. Barbara Sciascia on behalf of Charged Kaon Working Group KLOE General Meeting

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K  two body decays

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  1. K two body decays • Absolute BR measurements • BR(K  ) B. Sciascia • BR(K  pp0) E. De Lucia • BR(K  pp0)/BR(K  ) • M. Martemianov, V. Kulikov Barbara Sciascia on behalf of Charged Kaon Working Group KLOE General Meeting Roma - November, 14th 2003 B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  2. K   decay:state of the art • Highest K branching ratio (63%) • - A single measure exists (Chiang ‘72) • Tag for absolute BR measurements • - Tag Bias • - m-Trigger • - Correlation effects • - Cosmic veto/T3 correction • 2001 and 2002 Data B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  3. Event selection • Algorithm 5th: TagDecay • Preselection: • -zPCA  20cm • - rPCA  10cm • - pK (70,130) MeV • Selection: • - rVTX  (40,150) cm • - dp  (-320,-120) MeV • - p(mp)  (180,270) MeV • Reconstruction: • FilFo •  • Tracking 1 •  • EvCl 1 (5 Algos) •  • “Kaon joining” •  • EvCl 2 (5 Algos) •  • Tracking 2 • Systematics: to be studied B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  4. Caveat: KLOE MC truth K KLOE MC truth K- K nucl. interaction not well simulated under 400-500 MeV Measured by KLOE? (see Patera talk) Tag: K- Signal: K B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  5. Tag and signal selection • Tag • - “recover” K from EvCl2 • (TagDecay) • - p(mm): 3s cut • - Trk-to-clu for m-track • - 2 trigger sectors fired • by the m • Sig (DC only) • - Look for K (TagDecay • preselection) • - V2 vertex • - rVTX  (40,150) cm • - p(mm): 3s cut B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  6. K  Tag Bias DC selection (p, mm mass hypothesis) Trk-to-Clu for m track m-cluster fires 2 trigger sectors (AutoTrigger) Tag K Signal K Tag K Signal K MC: 4 pb-1 for 20 pb-1 of Data K  p pTag Bias at the same level B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  7.  on calorimeter: Data and MC muons pions B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  8. Efficiency - Tag in one side - One “m-cluster” different from the tag one: 0 cluster with ECLU(EA,EB) MeV 1 cluster with ECLU(EB,EC) MeV • MC: EA = 20 MeV • EB = 120 MeV • EC = 370 MeV • Data: EA = 20 MeV • EB = 90 MeV • EC = 320 MeV • MC vs MC: • eMC Truth = (28.9  0.1) • eMC-like-Data = (30.1  0.1) • eMC-like-Data Corr = (28.8  0.1) B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  9. DC HW efficiency Present MC eff. Layer “Correlation” • Tracking seems to correlate Tag • and Signal emispheres • Try an estimation from MC • Method: • Define a “kind of correlation”,  : • Correction to be applied: -  from MC -  from Data - typical value: 1.0460.002 (4pb-1of MC, 20pb-1 of data) B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  10. Branching ratio • MC (4pb-1) vs MC (4pb-1): • - BR(K) = (63.46  0.40) • - BR(K--) = (62.44  0.40) • - Remind MC truth: • 63.46  and 61.32  • Cosmic veto/T3 efficiency: 0.2% Very preliminary, for K+. . . waiting for new MC: HW DC eff. and m/p on calo • BR(K) = (64.84  0.08) • BR(K--) = (63.88  0.08) B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  11. Strategy • Self-tag on one side using K- (avoid nuclear interactions) • Vertex with 2 tracks in DC on the signal side Status of K±p±p0 E. De Lucia Method: Fit the distribution of the momentum of the secondary track (p*) in the kaon reference frame • The selection efficiency is only related to DC reconstruction : • tracking efficiency (see Patera’s talk) • vertex efficiency (ongoing work to be finalized) B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  12. Difference between Tags x10-2 tag mn – pp0 tag mn tag pp0 p* (MeV/c) p* (MeV/c) B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  13. p* (MeV/c) DATA vs MC p* (MeV/c) • Clear resolution effects…two possibilities • work on resolutions MC wrt DATA • 2) use two “m-clusters” sample B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  14. p*(p mass): mn peak pp0 peak fit with p*(m mass) MC MC p* (MeV/c) p* (MeV/c) 2) Use the two”m-cluster” sample • hp:pp0 and mn peaks have the same resolution function • p*(p mass) distribution for mn peak • p*(m mass) distribution for pp0 peak B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  15. In order to extract the number of pp0decays: • Estimate the mn background • - require a p0 in the calo and measure the efficiency • Take into account the 3-body decays contribution • - fit the distribution down to 180 MeV in order to have • 3-body decays contribution  only from kl3 channel Perform the fit: • using the MC shape • parametrize it with a Fermi-Dirac distribution (first MC tuned) B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  16. MC p* (MeV/c) a) using MC shape for 3-body decays DATA 2/ndf = 1.08 2/ndf = 0.96 p* (MeV/c) fit lower edge 180 MeV B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  17. MC p* (MeV/c) p* (MeV/c) b) using Fermi-Dirac shape for 3-body decays MC fit lower edge 180 MeV Work in progress pp0 and mn populations agree within errors B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  18. Analysis of ratio BR(K  0)/BR(K ) M. Martemianov V. Kulikov •  - hyphotesis for secondary particles • Selected  - window : 190 - 220 MeV/c • Selected  - window : 220 - 260 MeV/c • Ktrigger - trigger efficiency, extracted from EXP. data • Kfit- efficiency of signals and background rejection, based on MC data and performed of EXP data, • Ksel- selection efficiency, from MC and EXP. data • Kvetocos - efficiency of cosmic veto rejection, EXP. data B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  19. Analysis of ratio BR(K  0)/BR(K ) • Both triggers employed • New checks on Ktrg and Kcos • Result is in good agreement with world data • Statistical error negligible due to the huge sample of kaon decays (more than 6.5 M; 2002 Data). • Systematic error ( 0.65 %) dominates. • Result can be updated by further investigation of MC/EXP uncertanties • Include calculation of K  decay B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

  20. Conclusions • Br(K  ): measurement on a good shape • Br(K  pp0): ongoing work • Br(K  pp0)/Br(K  ): memo in preparation • Different techniques have been implemented • Systematics: to be finalized. . . • New MC (see M. Moulson presentation): • - Small sample • - HW+Tracking efficiencies (by S.Dell’agnello, ready) • -  on EMC (by C.Bloise, M.Testa, and T.Spadaro, ongoing work) • Improve correlation study • Selection effects: • - FilFo • - Trk 1/Trk 2; EvCl 1/EvCl 2 • Efficiencies: a lot of work . . . • Tags in a good shape for absolute BR measurements B.Sciascia KLOE General Meeting - Roma - November, 14th 2003

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