Cosmic-ray Generator and comparison with BFEM data

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Cosmic-ray Generator and comparison with BFEM data

• Nov 26, 2001
• Tsunefumi Mizuno

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Overview of this study

• Main purpose of this work is to construct
  reliable Cosmic-Ray generator and BFEM simulator.
  They are essential for background prediction of
  GLAST satellite.
• Simulator and generators were first constructed
  by K. Hirano (simulator) and M. Ozaki (CR
  generator), and now being developed by H.
  Mizushima, T. Mizuno and Y. Fukazawa.
• CR proton, electron, positron, gamma and muon
  generators are constructed.
• Trigger rate, Hit distribution in TKR and
  reconstruction are utilized to improve the
  simulator and generator.

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CR generator(proton/e-)
CR proton

• Uncertain
• Spectrum below 100 MeV
• Angular dependence of secondary
• (10.6sin(theta) is assumed)
• Attenuation by the air (primary)
• East-west effect (not implemented)

CR electron
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CR generator (e/gamma/muon)

• Uncertain
• Spectrum below 100 MeV (e)
• Angular dependence of e/muon
• COR dependence of muon
• Angular dependence of gamma
• Spectrum of gamma

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Comparison with BFEM data
Data
muon()
muon(-)
gamma
positron
electron
proton
L1T rate 500Hz (data)/ 550Hz (simulation)
neutral event rate (lt0.5MeV in ACD) 60Hz (data)/
68Hz (simulation)
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Modifying gamma-ray distribution (sharper earth
rim)
neutral event rate 60Hz (data)/ 55Hz
(simulation)
downward upward
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CR proton/muon filter (1)

• The filter is developed by Michael Roterman
• Only single and straight track is selected
  (proton/muon)
• Select events based on hit in ACD and number of
  hits in TKR layers are

MC Protons Red MC Muons (- ) Yellow BFEM
data blue

• Any one of top ACDs is hit
• 8 or more TKR layers are hit

• Vertically downward proton/muon
• Good agreement between data and simulation

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CR proton/muon filter (2)

• Any one of side ACDs is hit
• 4 or more TKR layers are hit

• proton/muon come from horizon is selected
• Simulation overestimates data

MC Protons Red MC Muons (- ) Yellow BFEM
data blue

• Angular distribution of secondary is uniform
  rather than 10.6sin(theta)?

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Narrow gamma-ray and uniform secondary charged
particles
Data
muon()
muon(-)
gamma
positron
electron
proton
L1T rate 500Hz (data)/ 450Hz (simulation)
neutral event rate 60Hz (data)/ 50Hz
(simulation)
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Other issues to be examined

• Low energy spectrum (especially e- and e)
• Apply gamma-ray filter (with Kotani-san _at_ GSFC)
• Attenuation by air (primary proton)
• Brush-up geometry (outside Pressure Vessel)
• Physics process of Geant4 (studied by Ogata/Kamae)