1. KEK, 阪大RCNPA, 阪大理B, 京大理C, 原研先端研D,
福井大E, 防衛大F,　AlbertaG, UBCH, BNLI, FNALJ,IHEPK,
INRL, UNMM, SUNY Stony BrookN,TRIUMFO
関口哲郎，大橋永治，小林正明，小松原健，笹尾登C，新川孝男F，
杉本章二郎，玉川洋一E，常見俊直，中野貴志A，能町正治B，
野村正C，藤原庸博C，溝内健太郎C，村松憲仁D，吉岡瑞樹，
吉村喜男，他 BNL-E949 CollaborationA,B,C,D,E,F,G,H,I,J,K,L,M,N,O
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

2. 59th JPS Annual Meeting, Kyusyu Univ.
1. Physics Motivation
(Flavor Changing Neutral Current: FCNC) l
Vtd
Second order: Top quark dominant
Vtd vertex
Theoretical uncertainty
Good decay to measure |Vtd| in K+ system
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

3. 59th JPS Annual Meeting, Kyusyu Univ.
1.1 Search for
Two events were observed from BNL-E787.
Observation
SM prediction
Mean value is twice higher,
but consistent within error.
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

4. 59th JPS Annual Meeting, Kyusyu Univ.
2. BNL-E949 Experiment
2.1 Search Region
BNL-E949: Successor to BNL-E787.
Aim: Collect more signal events.
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

5. 59th JPS Annual Meeting, Kyusyu Univ.
2.2 E949 detector
Stopped K+ experiment
Delayed Coincidence
Wait 2ns after K+ enters detector
2 ns
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

6. 59th JPS Annual Meeting, Kyusyu Univ.
2.2 E949 detector
Pulse analysis with Waveform Digitizer
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

7. 59th JPS Annual Meeting, Kyusyu Univ.
2.2 E949 detector
Upgrades in E949 detector …
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

8. 59th JPS Annual Meeting, Kyusyu Univ.
2.4 Data Taking
Physics run: 2002, February ~ June
~12 weeks
~1/3 of E787 data
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

9. 59th JPS Annual Meeting, Kyusyu Univ.
3. Background Study
Analysis Strategy
Main Background
Blind Analysis
Real data
Likelihood Analysis
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

10. 59th JPS Annual Meeting, Kyusyu Univ.
3.2 Likelihood Analysis
T. Junk method: [NIM A434, 435 (1999)]
Calculate confidence level (C.L.) with a small statistic (Poisson stat.).
Predefined Background Functions:
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

11. 59th JPS Annual Meeting, Kyusyu Univ.
3.3 Background and Sensitivity
Background summary
Background
Events
Beam
Total
Sensitivity
Total Acceptance (10-2)
NK (1012)
Sensitivity (10-10)
Ready to open the BOX !
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

12. 59th JPS Annual Meeting, Kyusyu Univ.
4. Opening the BOX
An event is observed near upper kinematic limit.
E=128.9 MeV
P=227.3 MeV/c
R=39.2 cm
Other variables are fine.
S/N ratio for this event
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

13. 59th JPS Annual Meeting, Kyusyu Univ.
4.1 Branching Ratio Calculation
Combine E787 and E949 data
0.07
0.006, 0.02
Background Prob.
0.48
0.98, 0.88
0.9
50, 7
Si / bi
2002A
1995A, 1998C
Candidate NK
E949
E787
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

14. 59th JPS Annual Meeting, Kyusyu Univ.
5. Summary
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

15. 59th JPS Annual Meeting, Kyusyu Univ.
Backup Slides
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

16. 59th JPS Annual Meeting, Kyusyu Univ.
Event Display
2002A
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

17. 59th JPS Annual Meeting, Kyusyu Univ.
Pulse Shape in Stopping counter
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

18. 59th JPS Annual Meeting, Kyusyu Univ.
Event Display No.2
1998C
1995A
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

19. 59th JPS Annual Meeting, Kyusyu Univ.
E949(02): Combined E787&E949.
E949 projection with full running period.
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

20. 59th JPS Annual Meeting, Kyusyu Univ.
How much impact on |Vtd| ?
68% interval
Central value
90% interval
Picture by G. Isidori
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

21. 59th JPS Annual Meeting, Kyusyu Univ.
How many events do we need ?
E949 proposal: ~10 events give ~30% relative error
~40 events give ~16% relative error
CKM proposal: ~100 events give ~10% relative error
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

22. 59th JPS Annual Meeting, Kyusyu Univ.
Likelihood Analysis
The definition of X
The Poisson probability for Si + bi or bi to give di
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

23. 59th JPS Annual Meeting, Kyusyu Univ.
Likelihood Analysis
Then obtain the confidence level.
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

24. 59th JPS Annual Meeting, Kyusyu Univ.
Likelihood Analysis
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

25. 59th JPS Annual Meeting, Kyusyu Univ.
Typical Second Pulse Time for Signal and Background
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

26. 59th JPS Annual Meeting, Kyusyu Univ.
Momentum Spectrum of some K+ decay modes
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

27. 59th JPS Annual Meeting, Kyusyu Univ.
Background Sources
Background Source
Reasons
Target cut
Photon missing
Kinematics mismeasure
- Photon Veto
- Phase Space cut
Beam related
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

28. 59th JPS Annual Meeting, Kyusyu Univ.
Bifurcation Method
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

29. 59th JPS Annual Meeting, Kyusyu Univ.
Correlation check
Loosen two cuts simultaneously or independently
Compare observation and prediction outside the box.
Prediction
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

30. 59th JPS Annual Meeting, Kyusyu Univ.
Correlation Check 2
Compare Observed and Predicted in each loosened box
10.4
5.2
3.2
1.3
0.31
Predicted 11 5 4 1
Observed
21.8
14.5
9.1
1.4
0.35 25 16 12
62.4
31.1
12.4
4.9
1.1 53 22 9 3
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

31. 59th JPS Annual Meeting, Kyusyu Univ.
Correlation Check 3 (Statistical treatment)
Fitting to the Observed / Predicted with constant
0.40
0.67
0.17
Total Background c
Background
Correlation seems to be small.
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.

32. 59th JPS Annual Meeting, Kyusyu Univ.
End of Backup Slides
March 28, 2004
59th JPS Annual Meeting, Kyusyu Univ.