1. Update of G4 simulation -- Development of Cosmic-Ray generator --
September 27 , 2001 Balloon Analysis VRVS meeting
T. Mizuno
H. Mizushima, H. Tajima, and T. Kamae

2. Overview of this study
Main purpose of this work is to construct reliable Cosmic-Ray generator and BFEM simulator.
We have been developing Cosmic-Ray generator, to reproduce observed L1T rate (~500Hz), neutral event rate (~50Hz), and hit distribution in TKR.
Just extrapolating electron spectrum down to 10MeV did not give a satisfactory result. (

3. L1T rate and neutral event rate
Electron Spectrum: Updated (see next page)
Positron spectrum and gamma-ray spectrum: newly implemented
L1T Rate
~230Hz~460Hz in total
Proton :~200Hz ~200Hz (same model)
Electron: ~25Hz~100Hz (updated, see next page)
Positron: not implemented~60Hz
Gamma: not implemented~100Hz
Neutral event rate
~5Hz~60Hz in total
Proton :~4Hz ~4Hz (same model)
Electron: ~1Hz~12Hz (updated, see next page)
Positron: not implemented~7Hz
Gamma: not implemented~40Hz

4. Updated CR spectrum
Electron spectrum: extrapolated down to 10 MeV with E^-1
Positron spectrum: based on AMS, similar to that of electron
Gamma spectrum: based on balloon/satellite measuremts.
(see below)
Downward gamma
E^-1
Downward electron
Please note that positron/gamma ray generator are
under development.

5. Distribution of Top-most hit layer
BFEM data vs. G4 simulation
Contribution of each component
positron
gamma
electron
Proton
 
Calorimeter
Top of TKR
Basically good.

6. Distribution of Hit Frequency
BFEM data vs. G4 simulation
Contribution of each component
positron
gamma
electron
proton
Basically good. Slight deviation is seen in layer

7. Distribution of Number of Layers with Hits
BFEM data vs. G4 simulation
Contribution of each component
positron
gamma
electron
Proton
Basically good.

8. Distribution of Hit Frequency for neutral events
BFEM data vs. G4 simulation
Contribution of each component
positron
gamma
electron
proton
Geant4 shows slightly higher hit frequency in layer 5-20.
We may need to adjust gamma-ray flux or angular distribution.

9. Summary
With CR proton, updated electron, positron, and gamma,
we can approximately reproduce the oberved L1T rate,
neutral event rate, and hit distribution in TKR.
Future plan
Implement CR muon.
Apply proton/muon cuts to both real data and simulation data, and adjust proton (muon) flux in generator.
See hit distribution in TKR and adjust gamma, electron and positron flux/angular distribution.