1. Geant4 simulation for Balloon Flight Jan. 16, 2001 Software Workshop at SLAC Tsunefumi Mizuno

2. In order to develop a G4 simulator for a Balloon Flight, we need to … Validate simulator---Physics process, comparison with Beam Test (SLAC/Hiroshima) Make a Cosmic-ray Generator (Masanobu at ISAS --- talk of Yasushi) Construct a geometry (Hiroshima) Study on tagged gamma-ray events (external target), background, etc… (Hiroshima) Others ? (please give your opinion)

3. Validation of G4 simulator – Physics process dE/dx (MeV cm^2/g) Kinetic Energy (MeV) Proton in Si We also plan to examine dE/dx in a thin material (Landau distribution) Photon cross-section Low-energy option (fluorescent X-ray) ………. Others?

4. Validation of G4 simulator– comparison with BeamTest (99) BeamTest(99) TBsim Geant4 Similar but slightly different (G4 shows smaller # of hit)

5. Study on Balloon Flight— Tagged gamma-ray event at Target Procedure: –Bomber Proton on Target –Search event where pi0 is generated at target –Check out whether decayed gamma-ray is converted at Tracker or not

6. Expected number of tagged photons Target threshold: ~50 MeV 50 events/1M proton (~2hour) ~ 200events/8 hour

7. Study on Balloon Flight— Background ( low statistics at the moment) Bombard electron to Pressure Vessel 100k electron (1-2s) 1340 events meet Level 1 Trigger (most of them are rejected by ACD veto) Candidate for background event (bremsstrahlung at PV): a few events/100k electron

8. Summary and Conclusions We are now validating G4 simulator. We have already included Pressure Vessel and VME Crate in G4 geometry. An implementation of Gondola is under progress An expected number of tagged-photons is about 200/8 hour flight Background estimation is started.