Simulation and comparison with BFEM data

1
Simulation and comparison with BFEM data

• Nov 29, 2001
• Tsunefumi Mizuno, H. Mizushima, Y. Fukazawa, H.
  Handa, T. Kamae and M. Roterman

2
Overview

• Status before IEEE meeting, see simulation
  posters at http//www-glast.slac.stanford.edu/LAT/
  balloon/reports. We compared L1T rate, neutral
  event rate and hit distributions in TKR.
• We modified ACD threshold referring to Bobs
  presentation (Oct 18, 2001).
• We also studied angular distribution of
  proton/muon. See also Tunes report
  (ReportSoftWorkShop2Nov01.ppt).
• In order to solve the discrepancy between the
  data and simulation, we modified angular
  distribution of gamma-rays and secondary
  charged-particles. See also Tunes report at
  software workshop (ReportSoftWorkShop2Nov01.ppt).
  There, ACD threshold is set as PHA250 for all
  tiles.

3
ACD PHA threshold
Simulation 0.5 MeV (neutral event rate is not so
sensitive to threshold level) Data constant
(PHA250) -gt 25 of MIP peak (see below)
TILE PHA 000 298 001 299
010 267 011 312 100 308 110
317 200 290 210 411 300
318 310 325 400 291 410 314
1000 290
Neutral event rate 50Hz(old) -gt 60Hz
If you find any mistake, please inform me.
4
Gamma-ray angular distribution

• Revised ACD thresholds are used for data
• Agreement between data and simulation improved

broader distribution
narrower distribution
muon()
muon(-)
Data
gamma
positron
electron
proton
5
Angular distribution of proton/muon

• Select events of straight and single track
  (chi2lt0.2 in reconstruction)
• Any one of ACDs is hit
• 4 or more layers (among lower 16 ones) are hit

10.6sin(theta)
uniform
MC Protons Red MC Muons (- ) Yellow MC e-
green BFEM data blue
MC Protons Red MC Muons (- ) Yellow MC
e-/e green BFEM data blue
cos(theta)
(horizontally)
(downward)

• Angular distribution of secondary is uniform
  rather than 10.6sin(theta)?
• Simulation still exceeds data at
  cos(theta)0.2-0.4. Primary protons are
  attenuated by the air? (Particles comes from
  horizon suffer large attenuation)

6
TKR hit distribution with narrow gammas and
uniform secondary charged particles
Data
muon()
muon(-)
gamma
positron
electron
proton
neutral event rate 60Hz (data)/ 50Hz
(simulation)
L1T rate 500Hz (data)/ 450Hz (simulation)

• Agreement between the data and simulation is
  still unsatisfactory.

7
Summary

• We are now tuning the cosmic-ray model using BFEM
  data
• Secondary charged particles seems to be uniform
  rather than proportional to 10.6sin(theta) (yet
  to be examined)
• Gamma-ray angular distribution may be
  constrained.
• Agreement with data and simulation is yet
  unsatisfactory.
• Low energy spectrum (especially e- and e)?
• Attenuation by the air (primary proton)?
• Physics process of Geant4?