Final Results Ratio of ke3/pipi0

1. Final ResultsRatio of ke3/pipi0 Anne Dabrowski Northwestern University NA48/2 Collaboration Meeting 08 June 2005

2. Outline • Data & MC samples • DATA / MC of final selection • Trigger Efficiency • Particle ID efficiency • Br results • K+ / K- • Error analysis • Statistical contributions • Inputs from PDG (pipi0 Br) • Systematic Errors, stability under variation of selection cuts, and form factor (λ+) • Final result • Conclusion

3. Data and MC samples Data: • Compact 7.2 & Database (database-2005-02-11) pass 5 Min bias 2003 (runs 15745,15746 and 15747) • Bad burst • Check: DCH,MBX,HODC,LKR,MUV,PMB and MNP33Current ne 0) • Reject 31 bursts for which momentum = 10.0 GeV • Total number of bursts after bad burst rejection: 2244 • Alphas and betas • Projectivity and Blue Field (Alan algorithm to remove phi dependence) • Note: Result from August 2004 (ICHEP), used Compact 7.1 (no baseline energy correction) MC Sample: • Ginsberg correction • Constants from PDG 2004 ( λ+ = 0.02780) • Pi0 decays according to its branching ratio • CMC005 corrections including corrections of May 9th 2005 • Result based on sample size of 10 M pipi0 and 8 M ke3 • Pipi0 mc has 0.438% pipi0g (IB) included in it at generation level • Note Result from August 2004 (ICHEP) used cmc003 (improved DCH resolution in cmc005 among other changes) based on 2 M pipi0 and 2 M ke3. Dalitz and non dalitz decays were generated separately, pipi0 and pipi0g generated separately and ( PDG 2002 λ+ = 0.02760) was used as input to MC

4. Track Section (no extra tracks allowed): 1 track after excluding Ghost-tracks Hodoscope time window (-17. 20. ns) Track quality > 0.8 CDA < 2.5 , Beta, alpha corrections from database x,y vertex (-1.8,1.8) cm , z charge vertex (-500,8000) cm Blue Field correction applied Pi0 Selection (extra gammas allowed for both) Energy of gamma (3, 65) GeV Separation between gammas > 10 cm Time difference between gammas (-5., 5.) ns Energy scale Projectivity correction Calculate neutral vertex for each pair of gammas, and choose gammas based on best difference between charge and neutral vertex Use this neutral vertex in the blue field routine to correct the slopes of the track (reason: phi dependence studies of Alan) August 2004 (ICHEP) result used the “charge” vertex reconstruction, and cut on pi0 mass as function of energy Common Selection for Ke3 and pipi0

5. Kaon Mass < 0.4772 or > 0.5102 (3 sigma from the mean) Momentum (5, 35) GeV PT track (0.01, 0.2) GeV Nu mass (-0.012, 0.012) GeV2 Dist between track & gammas > 10 cm COM Track < 0.22 GeV COM pi0 < 0.27 GeV Mass (eπ0 ) < 0.425 GeV Particle ID for electrons: EOP > 0.95 Difference between Ke3 and pipi0 Selections • Kaon Mass (0.4772,0.5102) GeV • Momentum (10, 50) GeV • PT track < 0.215 GeV • Nu mass (-0.0025, 0.001) GeV2 • Distance between track & gammas > 35 cm • PT pi0 < 0.220 GeV • E/P < 0.95

6. Summary of particle ID used:

7. Ke3 Data / MC Momentum track Once the momentum dependent E/P particle ID efficiency is taken into account  distribution OK

8. Ke3 Data / MC Energy Pi0  Good energy calibration LKr

9. Ke3 Data / MC PT of pi0 sensitive to backgrounds and neutral reconstruction  seems OK

10. Ke3 Data / MC PT of track sensitive to backgrounds  seems OK

11. Ke3 Data/MC COM energy pi0 sensitive to backgrounds  seems OK

12. Ke3 Data/MC COM energy track sensitive to radiative corrections, Ginsberg implementation of radiative corrections OK!

13. E/P > 0.95 for electrons Global efficiency (97.37 ± 0.09) % E/P < 0.95 for pions Global efficiency (99.522 ± 0.001) % Electron ID and Pion ID • Selected electrons from tight ke3 selection and pions from tight pipi0 selection • Used same data sample, and timing and fiducial cuts as in analysis

14. Background contributions Recall: electrons rejected by E/P in pipi0 pions rejected by E/P in Ke3 muons rejected in Ke3 only Muons allowed • Kmu3 background can be made negligable if we want to reject muons … see kmu3 talk.

15. Summary of acceptance and background • Kmu3 background can be made negligable if we want to reject muons … see kmu3 talk.

16. Sources of background to ke3 K+/K-

17. Sources of background pipi0 K+/K-

18. Calculating the Ratio (ke3/pipi0) We have all the ingredients for calculating the ratio … • Other corrections needed: • Trigger Efficiency • Correction to radiative decays • Pipi0γmixed with pipi0 at generation level i.e. no further correction needed, correctly described by acceptance • Ke3γGinsberg correction, events only generated inside dalitz plane. Need to correct acceptance for Ke3γ events in data lie outside dalitz plane

19. Trigger Efficiency K+/K- • Main Trigger Q1/4 • Min bias trigger for trigger efficiency calculation Trackloose/100

20. Correction Ke3g K+/K- Ke3(γ) events inside dalitz plane • Events are only generated (and corrected for radiative events) inside the dalitz plane in ke3 MC. Hence we need to correct for the acceptance of ke3(γ) for events in the data which lie outside of the dalitz plane. • Look at data  events in v.s. out of dalitz plot • K+ • events selected out:152 • Events selected in: 57550 • Correction to Ke3 acceptance 1.0026±0.0002 • K- • Events selected out: 63 • Events selected in: 31683 • Correction to Ke3- acceptance 1.0020± 0.0004 • Assume that in the data, all events outside of the dalitz plot are ke3g candidates, have not corrected this ratio yet for possible sources of background – but this is assumed small Ke3γevents outside dalitz plane

21. Result (Ratio Ke3/pipi0) K+/K- Recall PDG 2004: Br(Ke3) = 0.0487± 0.0006 Br(pipi0) = 0.2113 ± 0.0014 Fit Ratio(ke3/pipi0) = 0.230±0.004 • The error in the Br includes: • Statistical (signal and normalization) • Systematic • Trigger efficiency • MC statistics (10 M pipi0 and 8 M ke3 of each charge) • Errors in particle ID efficiency (particle ID error bin by bin and propagated) • Errors due to background subtraction (including particle ID) • No additional systematic errors due to kinematic cuts or form factor changes have been includedYET in this table

22. Details of error contributions to ratio K+/K-

23. Summary of results:

24. Do we have any addition effects?

25. Check Ratio of Ke3/ pipi0 as a function of momentum K+ K- Χ2/ndf 9.155 / 11 Χ2/ndf 12.25 / 11 The ratio is stable as a function of momentum (plotted in momentum region where ke3 and pipi0 events overlap)

26. Ke3 Data / MC Vertex problem at high vertex, seems to be feature for K+ and K- What is the source? Does it affect our result?

27. Beam Tuning Recall August 2004 • DATA/MC was for vertex in August was fine at high vertex (cmc003, and my beam tuning for special run) • Now use default cmc005, and beam tuning only done for assymetry runs (hypercompact)… • High vertex is an effect of insufficient beam tuning for our run. • But Does it affect our result?

28. K- K+ Effects due to choice of vertex cut? Analysis fuducial volume (-500 , 8000) cm Check I (-1000 , 7000) cm Result of fit doesn’t depend on fiducial region  result insensitive to vertex

29. K- K+ Effects due to choice of vertex cut? Analysis fuducial volume (-500 , 8000) cm Check II (0 , 8000) cm Result of fit doesn’t depend on fiducial region  result insensitive to vertex

30. Effects due to choice of vertex cut? Result of fit doesn’t depend on fiducial region  result insensitive to vertex

31. Energy γ1 Energy γ 2 Low neutral energy scale Recall, in August checks  shift in ratio 0.00095 due to final calibration missing in compact 7.1

32. Varying the form factor λ+ K+/K- Propose: add systematic 0.0002 to cover 0.0271 K+ result

33. Summary Systematic checks

34. Details of error contributions to ratio K+/K-

35. Summary of results  Result dominated by statistics not systematics!