1. Understanding of the E391a Detector using KL decay
Ken Sakashita
( Osaka University )
for the E391a collaboration
Overview
KL → 3p0 analysis
KL beam & Detector study
Conclusion

2. Overview(1) Engineering Run Detector & KL beam understanding
CsI
Charged Veto
Collar counter (CC03)
Edge counter
Detector only downstream part
Detector & KL beam understanding
Data sample vs MonteCarlo
KL 3p0
Confirm our MC simulation
We need confirmed MC simulation in order to study
acceptance and so on.

3. Overview(2) Data sample (only 3 hours run used in this study)
Mainly KL 3p g
Energy measured by CsI calorimeter
Only neutral decay mode
( no spectrometer !!)
MonteCarlo Simulation
Input KL beam
(avr. P =
GEANT3 based Detector simulation
Method
Reconstructed KL events
Simple clustering (typically 3x3)
Reconstructed KL 3p0 with good vertex chi square
0.46 < MKL (GeV) < 0.53
Generated by
Beam line Simulation
KL momentum (GeV/c)

4. KL->3p0 Data vs MC Wrong KL momentum distribution
Invariant mass of 6 g # of KL Data/MC = 0.74
Data MC
Wrong KL momentum distribution
Is the problem due to input KL momentum or
detector response ?
Compare in 0.5 GeV energy bin

5. KL->3p0 Data vs MC( 0.5GeV EKL bin)
Vertex Z distribution
Sensitive to energy response
Data MC
Data MC

6. KL->3p0 Data vs MC( 0.5GeV EKL bin )
Minimum distance between clusters
Sensitive to energy response
Data MC
Data MC

7. KL->3p0 Data vs MC( 0.5GeV EKL bin )
Cluster Hit Position (distance from the center)
Sensitive to detector response
Data MC
Data MC

8. Reweighted input KL momentum
MCは、よく　detector　を再現しているように見える。
実験で得られた KL momentum を、
MC の　input KL momentum に反映させてみる。
Data MC
KL momentum is softer than estimated one.
consistent with results of the Beam survey.

9. KL->3p0 Data vs MC( reweighted )
Vertex Z match well
Cluster Hit position ( Rij ) still match
Data MC
Data MC

10. KL->3p0 Data vs MC (reweighted)
PT2 distribution is not consistent with MC.
Beam shape D 2 ( )
is not also consistent with MC.
MC does not reproduce KL Beam shape well.
Data MC

11. Summary E391a detector is working well.
We can get good KL pencil beam.
Detector & KL beam understanding using KL->3p0
KL Beam
Yield Data/MC = 0.74
Momentum distribution
Softer than estmated distribution
It is consistent with the results of the beam survey
After reweighting Data vs MC match well
Beam shape
MC did not reproduce well. It needs more study.
Detector
More detail study in the next step

12. 予備OHPs

13. KL->3p0 Data vs MC( reweighted )
Cluster Hit position ( Rij ) still match
Minimum distance between clusters still match

14. KL->3p0 Z reconstruction
Make 3 gamma pairs from 6 clusters
Resonstruct Z vertex by asusuming Mp0 from 2g
Calculate vertex chi square for 15 combinations
of 3p0
Select best combination
for KL candidate

15. KL->3p0 Data vs MC( reweighted )
Beam shape ( vertex X,Y )
Data MC