1. PoGOLiteMC_2007-01-30.ppt 1 Updated MC Study of PoGOLite Trigger Rate/BG January 30, 2007 Tsunefumi Mizuno (Hiroshima Univ.) mizuno@hepl.hiroshima-u.ac.jp

2. PoGOLiteMC_2007-01-30.ppt 2 Objective of This Memo Trigger rate is crucial for DAQ design (data size, speed of data transfer, etc.). So does the residual background for performance evaluation and observation planning. The expected trigger rates and residual background are studied here by MC with the latest detector geometry and cosmic-ray flux model. This memo is intended to be used for future reference.

3. PoGOLiteMC_2007-01-30.ppt 3 Geometry Segmented side BGOs with Al housing and dual layer collimator Dimensions  antiThickness = 3 cm  bottomWidth = 2.85 cm  fastWidth/slowWidth = 2.775/2.770 cm  Al Case for side BGO, antiGap = 0.075 cm  Al Case for bottom BGO, bottomGap = 0.15 cm  No passive shield antiThickness bottomWidth bottomGap antiGap SAS in Al Case Slow scintillator and collimator Pb 50um(55cm) Sn 50um(60cm) Pb/Sn dual layer collimator

4. PoGOLiteMC_2007-01-30.ppt 4 CR model: charged particles e - /e + protons -/+-/+ Cosmic-ray BG flux model for GLAST BFEM (Palestine, Texas). See Mizuno et al 2004 (ApJ 614, 1113) for more detail.

5. PoGOLiteMC_2007-01-30.ppt 5 CR model: gammas CXB Atmospheric downward Atmospheric upward

6. PoGOLiteMC_2007-01-30.ppt 6 Summary of CR spectra (above 10 MeV) e - /e + protons -/+-/+ CXB Atmospheric downward Atmospheric upward

7. PoGOLiteMC_2007-01-30.ppt 7 Section1: Trigger Rate

8. PoGOLiteMC_2007-01-30.ppt 8 Anti Trigger Rate proton e-/e+ gamma CXB Atmospheric downward Atmospheric upward total Rate of events where any one of 54 units have a hit Rate of each unite

9. PoGOLiteMC_2007-01-30.ppt 9 Bottom Trigger Rate Rate of events where any one of 217 units have a hit Rate of each unite

10. PoGOLiteMC_2007-01-30.ppt 10 Fast Scintillator Trigger Rate Rate of events where any one of 217 units have a hit Rate of each unite

11. PoGOLiteMC_2007-01-30.ppt 1 Slow Scintillator Trigger Rate Rate of events where any one of 217 units have a hit Rate of each unite

12. PoGOLiteMC_2007-01-30.ppt 12 Section2: Background

13. PoGOLiteMC_2007-01-30.ppt 13 Simulation Condition Source Spectra E -2.1 spectrum with 100mCrab intensity, 20-200keV (300.8 c/s/m 2 ) 100% polarized, 6h exposure.Attenuation by air of 4g/cm 2 Detector Response (veto scintillators) Reject events with hit in slow/anti/btm scintillators. Eth=30 keV. No energy smearing taken into account yet. Detector Response (fast scintillator) 0.5 photo-electron/keV. Eth=2 keV fluctuated by poisson distribution, smeared by gaussian of sigma=0.5 keV (PMT energy resolution) Event Selection Two or three fast scintillators detected a hit. The largest energy deposit is considered to be photo absorption and the second largest energy deposit to be Compton scattering. (ignore the smallest energy deposit in 3 hits events.) Smear azimuth angle distribution with Hiro’s resolution function. No event selection on Compton kinematics

14. PoGOLiteMC_2007-01-30.ppt 14 Source and Expected BG Spectra 100 mCrab BG (total) CXB/downward/upward Signal exceed the BG up to 80 keV for 100 mCrab source and up to 140 keV for Crab Nebula. 20 keV 1 Crab

15. PoGOLiteMC_2007-01-30.ppt 15 Dependence on Bottom BGO/Slow Scintillator Threshold (1) Threshold of 30 keV is good enough to reduce the BG down to minimum level. 100 mCrab 1 Crab btmTh/slowTh = 10keV, 30keV, 100keV, 300keV and 1MeV

16. PoGOLiteMC_2007-01-30.ppt 16 Dependence on Bottom BGO/Slow Scintillator Threshold (2) Threshold of 10 keV(bottom BGO)/30 keV (slow scinti.) is good enough to reduce the BG down to minimum level. Threshold of 33 keV/100 keV is acceptable. 100 mCrab 1 Crab btmTh/slowTh = 3.3/10keV, 10/30keV, 33/100keV, 100/300keV and 0.33/1MeV

17. PoGOLiteMC_2007-01-30.ppt 17 Appendix: Standard Process vs. Low Energy Extention No significant difference between simulations with low energy extention and standard process. Fluorescent X-rays from Pb are well suppressed by Sn foil. 100 mCrab 1 Crab BG (total) with Low Energy Extention/Standard Process