1. Osaka University RCNP Toshinao Tsunemi
New Results on 　from E787
Osaka University RCNP
Toshinao Tsunemi
15 June 2005
KAON 2005

2. Outline 1) Introduction 2) BNL-E787 detector 3) Kinematic fit
4) Data reduction and background estimation
5) Spectrum Fitting
6) Systematic error
7) Summary
15 June 2005
KAON 2005

3. DE and IB component IB (Internal Bremsstrahlung) DE (Direct Emission)
(about 98%)
(about 2%)
IB (Internal Bremsstrahlung)
DE (Direct Emission)
BR(IB)=2.61*10-4 predicted by QED
(radiative correction)
15 June 2005
KAON 2005

4. W definition （K+ rest frame）
Opening angle
between p+ and photon
radiated photon energy
p+ energy
kaon mass
p+ mass
p+ momentum
15 June 2005
KAON 2005

5. W spectra DE
逆はreverce IB
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KAON 2005

6. History (55 < Tp+ < 90 MeV)
Theoretical prediction　O(p6)
Theoretical prediction O(p4)
theory: Chiral Perturbation Theory
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KAON 2005

7. The data was taken in the year of 1995. Number of kaons was 2.83×1011
About the published paper from BNL-E787 in the year of (S.Adler et al. Phys.Rev.Lett. 85,4856(2000))
The data was taken in the year of 1995.
Number of kaons was　2.83×1011
The result of DE branching ratio
This presentation（data taken in 1998）
１）more events than data in 1995
２）The trigger was modified to accept lower p+ momentum
15 June 2005
KAON 2005

8. BNL-E787 detector ) 12 cm K+ Kaon stopping Target
Main fibers K+
Edge fibers
Kaon stopping Target
5 mm square 41３ scintillation fibers )
Energy
Range in the Target
charged track
side view of the cylindrical detector
15 June 2005
KAON 2005

9. BNL-E787 detector K+ Drift Chamber (UTC) 3 active layers
Momentum of charged track
side view of the cylindrical detector
15 June 2005
KAON 2005

10. BNL-E787 detector ) K+ Range Stack 21 layers of plastic scintilators
Upper half of the cylindrical detector
Range Stack
21 layers of plastic scintilators )
Energy
Range
Charged track
side view of the cylindrical detector
15 June 2005
KAON 2005

11. BNL-E787 detector ) K+ Barrel photon detector
Upper half of the cylindrical detector K+
Barrel photon detector
Plastic & lead sandwich detector
4 layers
192 modules )
Energy
position
photons
side view of the cylindrical detector
15 June 2005
KAON 2005

12. Charged track spectrum
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13. trigger for K+→p+p0g Condition for Photon： Three or more clusters
Stopped in Layer4-6
＊ p+ condition in 1995：
Stopped in Layer7-10
Number of Kaon
　　　　　 　3.48×1011
（1995　2.83×1011）
15 June 2005
KAON 2005

14. Kinematic fit (most important cut)
6 constraints
Momentum conservation (x, y, z 3 constraints)
Energy conservation
mass p+
mass p0
13 variables
p+ p0 g 1 3 4
p + momentum
p + energy
Energy of photons
Azimuthal angle
Dip angle p+ g g g
1 pion and 3 photons
15 June 2005
KAON 2005

15. How to select two photons from π0
There are three combinations to
select two photons from p0
p+ p0 g p+ g g g
3 photons
Select the combination with the most c2 probability (Prob)
and the second most c2 probability calculated by
Kinematic fit.
Prob (Kinematic fit) ×matrix element(IB)2　is calculated
for the above combinations.
The combination with the larger value is assumed to be the
correct combination.
The percentage of correct combination is estimated by M.C. to be
97.2% and 83.4% for IB and DE, respectively.
15 June 2005
KAON 2005

16. Chi-square probability
accept
Chi-square probability
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KAON 2005

17. The power of kinetic fit
photon energy
before
after
MeV
MeV
M.C.
M.C.
MeV
MeV
Resolution 1.5 sqrt(E MeV) から0.50 sqrt(E MeV)
about
about
15 June 2005
KAON 2005

18. Resolution improvement on W
M.C.
M.C.
RMS 0.０25
RMS 0.05
15 June 2005
KAON 2005

19. Bgd rejection due to Kinematic fit
before
after
before
after
p+p0p0
accept
p+p0g
m+p0g
p+p0g
念のため　for comfirmation
π+ momentum
Charged track consistency
Measured - expected
15 June 2005
KAON 2005

20. Data reduction table π+ identification in the UTC & RS
π+ identification in the Target
Reject e+
Photon cluster is 3
Extra photon veto
Missing momentum
Photon clustering confirm
π+ mass
Photons are on time
Photon is in the fiducial region
Confirmation of trigger condition
W>0.1
Kinematic fit
Combination improve
140 MeV/c < Pπ+ <180 MeV/c
15 June 2005
KAON 2005

21. Background estimation by BNL-E787 standard method
All W
W>0.5
15 June 2005
KAON 2005

22. spectra fitting Number of events after all cut is 20571. 1) W spectra
2) Consistency between real and M.C. in W
3) Consistency in other spectra
4) Fitting result
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KAON 2005

23. W spectra
Real
IB(M.C.)
DE(M.C.)
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24. Consistency between real and UMC
M.C. reproduces the real data
in the region of W<0.4
where IB is dominant.
Real data
IB (M.C.) 2
/n.d.f=11.2/14
15 June 2005
KAON 2005

25. Consistency between Real & UMC
Real data
IB (M.C.)
Real and M.C data is compared
In the region of W<0.4
15 June 2005
KAON 2005

26. Spectrum fitting Real data is fitted by M.C.(IB+DE) *fitted by only IB
IB (M.C.)
IB+DE (M.C.)
observed/IB
Real data
IB+DE (M.C.)
Number of Event
統計エラーをしゃべること。
*fitted by only IB 2
/n.d.f=49.0/7 2
/n.d.f=7.6/6
result
The DE ratio to IB is RDE=0.070±0.011
15 June 2005
KAON 2005

27. Systematic error Total systematic error on RDE +18 % -23 %
Added in quadrature
15 June 2005
KAON 2005

28. Branching ratio of p+p0g
preliminary data in 1998
Previously published data from 1995
Combined value (preliminary)
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KAON 2005

29. Summary 1) BNL-E787 have data taken in 1995 and 1998.
2) Lower p+ momentum region is used in 1998, compared to the 1995 data.
preliminary
Consistent with theoretical prediction by Chiral Perturbation at O(p4) .
15 June 2005
KAON 2005

30. backup
Back up slides
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31. p+p0g spectra ? IB INT DE 1) Reducible O(p4) M: magnetic amplitude
２) VMD O(p6)
３) other O(p6)
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32. Trigger acceptance DE component (M.C.)
’98 DE events
’95 DE events
arbitrary unit
accept
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33. W Spectra W W IB DE
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34. Kinematic fit (stretch function)
Ideally, the distribution must be
a normal Gaussian.
(i.e the mean and sigma is 0 and 1.)
i=1~13
The resolutions are tuned for si to be from a normal Gaussian.
The measured value for M.C data is smeared to reproduce real date.
：random numbers to be formed to a normal Gaussian
example
15 June 2005
KAON 2005

35. Stretch functions π+ photon Azimuthal angle Dip angle energy momentum
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36. How to calculate branching ratio of p+p0g
Number of M.C. DE
Events for fitting
number of M.C. IB
Events for fitting
Ratio from fitting
IB acceptance calculated by M.C.
QED prediction for the IB branching ratio
DE acceptance calculated by M.C.
15 June 2005
KAON 2005

37. Summary 1) BNL-E787 have data taken in 1995 and 1998.
2) Lower p+ momentum region is used in 1998, compared to the 1995 data.
This experiment
consistent
Theory（only reducible term）
15 June 2005
KAON 2005

38. M　(no dimension)(1/2)
G.Ecker, H.Neufeld and A. Pich, Phys.Lett B278,337 (1992)
＊ f is a parameter of CｈPT at O(p2). f=93 MeV
15 June 2005
KAON 2005

39. M (no dimension)(2/2)
15 June 2005
KAON 2005