Cosmic-ray Generator and comparison with BFEM data Nov 26, 2001 Tsunefumi Mizuno
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.
CR generator(proton/e-) CR proton • Uncertain: • Spectrum below 100 MeV • Angular dependence of secondary • (1+0.6sin(theta) is assumed) • Attenuation by the air (primary) • East-west effect (not implemented) CR electron
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
Comparison with BFEM data Data muon(+) muon(-) gamma positron electron proton L1T rate 500Hz (data)/ 550Hz (simulation) neutral event rate (<0.5MeV in ACD) 60Hz (data)/ 68Hz (simulation)
Modifying gamma-ray distribution (sharper earth rim) neutral event rate 60Hz (data)/ 55Hz (simulation) downward upward
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
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 1+0.6sin(theta)?
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)
Other issues to be examined • Low energy spectrum (especially e- and e+) • Apply gamma-ray filter (with Kotani-san @ GSFC) • Attenuation by air (primary proton) • Brush-up geometry (outside Pressure Vessel) • Physics process of Geant4 (studied by Ogata/Kamae)