1. Space Applications of Geant4 Polarized Processes F.Longo + G.Depaola * + University of Ferrara and INFN (Italia) * National University of Córdoba (Argentina)

2. Outline Astrophysics with Polarized Photons Detectors in the Compton regime Simulation Requirements Geant4 processes ARGO: Compton or Pair telescope?

3. Polarized Gamma Astrophyics Compton Astrophyics (MeV region) Emission Mechanisms (Synchrotron Radiation, Bremsstrahlung, Compton Scattering, Photon Splitting) Astronomical Sites (Solar Flares, Galactic BH candidates, Pulsars, Plerions, AGN, GRB) See Review by Lei, Dean & Hills (1997)

4. Detectors in the Compton Regime Principles of operation Polarization measurements in the Compton regime

5. Polarization Detection Modulation Factor (azimuthal distribution of scattered photons  ) Figure of merit of Polarimeter Minimum Detectable Polarization See McConnell (ACT Workshop 2001)

6. COMPTEL Simulation in Geant3 - without the Spacecraft - EM only Background simulation Poor geometry small modulation factor See McConnell - Kippen (ACT Workshop 2001)

7. INTEGRAL Photo ESA See McConnell (ACT Workshop 2001)

8. Geometry

9. MEGA

10. Advanced Compton Telescope

11. See McConnell (ACT Workshop 2001)

12. X-ray polarimetry with MicroPattern Gas Detectors Costa et al. 2001

13. Simulation Effort Improved EM Physics Kinematic reconstruction of multiple Compton events Electron and pair tracking Background simulation efforts Image deconvolution See Kippen (ACT Workshop 2001)

14. Requirements Physical Simulation EM physics 1keV – 50 MeV Better description of Compton (doppler broadening and polarization) Hadronic cascades, spallation, isotope production, radioactive decay Time dependency Models of background Instrumental effects Reconstruction efforts See Kippen (ACT Workshop 2001)

15. Geant4: the answer? Unified framework (science, background, instrumental effects) Source & Background modelling Detector description Space modules Analysis tools

16. ARGO (Argentine Gamma Observatory) Proposal to Argentina National Agency for Scientific and Technological Development Payload weight (40-60 kg ~ AGILE) Power 60 W Use of Silicon Detectors Measurements of Polarization from Gamma Rays G4 crucial to evaluate the sensibility from Gamma Conversion or Compton Scattering