1. T. Ariga AEC-LHEP, University of Bern
Neutron detection with emulsion: update on data analysis and comparison with MC
T. Ariga
AEC-LHEP, University of Bern

2. Bern scanning laboratory
Data taking
Brick 1
Plate 1-120: 3cmx3cm, angular acceptance tan 2.0 (plate 1-25 updated)
last time:
Plate 1-25: 2cmx2cm, angular acceptance tan 1.7
Bern scanning laboratory
200 microns

3. Track selection (contained proton track)
MIP
Track selection (contained proton track)
Side in
Cut
Number of tracks
nseg>=2
805271
MIP cut
596481
Not side in
368517
Start plate >3
313422
Not side out
213039
Last plate <=117
187600
Not starting inside
Side out
Penetrating
Contained track

4. Some of selected tracks (1track/200tracks are shown)
1cm

5. MC reconstruction Neutron flux simulation Detector simulation
200k POT  2.1k neutrons
Detector simulation
5M neutrons
Measured efficiency applied
Track reconstruction applied

6. Comparison with reconstructed MC
Data
Cut
Number of tracks
POT normalized
nseg>=2 -
MIP cut
13464
1.000
756388
Not side in
8503
0.632
477686
Not side out
5345
0.397
300274
Last plate <=117
4680
0.348
262915
Cut
Number of tracks
nseg>=2
805271 -
MIP cut
596481
1.000
Not side in
368517
0.618
Not side out
213039
0.357
Last plate <=117
187600
0.315
Not bad?
Normalization to data:
Detector simulation POT for data Flux simulation

7. Proton energy distribution (shape)
Area normalized
Good agreement

8. Proton angular distribution
Not bad.
Difference may be within the uncertainty of MC.

9. Neutron spectrum unfolding (first trial)
Response function
Neutron energy
for detected protons (MC truth)
Neutron energy
unfolded from proton energy (data)
Not so good (yet).
The response function should be improved
with much higher MC statistics!

10. Summary
Data/MC comparison seems reasonable, considering the uncertainty of MC.
Larger MC statistics (x100) is needed (by AEC cluster).
Possible publication next months?

11. BACKUP

12. Angular acceptance vs proton efficiency

13. Reconstructed tracks (1track/1000tracks are shown)
120 plates, ~9 cm
Tracks with more equal 2 consecutive plates will be used in this analysis (E>~10MeV)
1cm

14. BG tracks

15. BG tracks have different alignment from neutron.
Proton alignment
New alignment
for BG tracks

16. Proton track selection (rejecting MIP)
tan(qY)
dE/dx
W(mean)
High dE/dx tracks
= protons
MIP tracks
= muon, electrons
tan(q)

17. Side in / side out

18. Some of selected tracks

19. Proton energy estimation (S. Golovanov)
For emulsion
Density (g/cm3)
OPERA emulsion
2.7
Base
1.3
Separator
1.06

20. Energy measurement