1. S. Y. Lee Pusan National University
CsI calibration using pi0 's produced by neutron-nucleus interaction ( KEK-PS E391a experiment )
S. Y. Lee
Pusan National University

2. E391a Collaboration High Energy Accelerator Research Organization, KEK
Faculty of Science and Engineering, Saga University
Department of Physics, Yamagata University
Department of Physics, Osaka University
Research Center for Nuclear Physics, Osaka University
National Defense Academy of Japan
Department of Physics, Ibaraki University
Joint Institute for Nuclear Research (Dubna) Russia
Department of Physics, University of Chicago
Fermi National Accelerator Laboratory
Department of Physics, Pusan National University

3. I. Motivation KL po n n gg Nothing pure CsI calorimeter 4p veto system
CALIBRATION to EM Calorimeter

4. II. Methods invariant mass of p0 produced by neutron
nucleus interaction at Al target n p0
Pure CsI
Arrays

5. Iteration Process Do i=1, 576
for given CsI Module
Reconstruct invariant mass from all 2 g event ( , other)
Take mean from the invariant mass distribution
Make correction factor
ENDDO
Update gains by respectively
Iterate above process
until to get correct invariant mass peak of p0

6. (continued) Data Sample 3 m : ~ 1.5 M reconstructed events
according to distance between Target and CsI calorimeter
3 m : ~ 1.5 M reconstructed events
7 m : ~ 1.5 M reconstructed events

7. III. Correction to Incident Position and Angle(by M.C.)
1. Position correction at normal incident
Center of gravity(cm)
Center of gravity
Incident position (cm)
Incident position (cm)
Before correction
After correction

8. 2. Correction to position and angle
Center of gravity (cm)
X axis : incident position(cm)
Y axis : center of gravity(cm)
Incident position (cm)
Before correction
After correction

9. 3. Results (position and angular correction)
MeV/c2
MeV/c2
Before correction
After correction
= 5.4 MeV/c2
= 4.1 MeV/c2

10. IV. Iteration
MeV/c2
MeV/c2
Before Iteration
After Iteration

11. Results (Iteration) RMS of Mass Peak of Each CsIs = 1.05 MeV/c2
Before Iteration
= 4.1 MeV/c2
RMS of Mass Peak of Each CsIs
= MeV/c2
~ MeV/C2
After Iteration
= 3.7 MeV/c2
RMS of Mass Peak of Each CsIs
= MeV/C2
~ 540 MeV/C2

12. Gain Change (preliminary)
MeV/pC
MeV/pC
After Iteration
mean : 2.7 MeV/pC
Before (from muon)
mean : 2.3 MeV/pC

13. V. Summary We improve the precision of CsI Calibration
Position and Angular Corrections
More Correct position of Gamma
Better reconstructed pi0 mass peak
( 25 % improvement of sigma )
Iteration Process
Additional 10 % improvement
Update gain constant
Proper mass peak position of p0 and

14. Differential Angular Correction
cog(q=n) - cog(q=n-1)
Incident position (cm)

15. Correction Factor For given CsI module , Assume
If gain is fully calibrated,
Take the ratio
, Assume
We can get ,

16. Basic Properties of Pure CsI
: 4.53
: 1.85
Moliere : 3.8
: 5.6
: 36.5
: 36f, 620s
: 305f, ~480s
: 1.80
light output(rel) : 0.10f, 0.20s (4k )f

17. Mean value distribution ( mass peaks of reconstructed pion mass distribution of CsIs)
MeV/pC
MeV/c2
MeV/c2
Before (from muon)
RMS : MeV/c2
After Iteration
RMS : 0.5 MeV/c2

18. = 5.3 MeV/c2 = 4.1 MeV/c2 3. Results-more Before correction
After correction
= 5.3 MeV/c2
= 4.1 MeV/c2

19. Gain Change (preliminary)