Geant4 electromagnetic physics progress

Abstract

The Geant4 electromagnetic (EM) physics sub-packages are a component of LHC experiment simulations. During long shutdown 2 for LHC, these packages are under intensive development and we report progress of EM physics in Geant4 versions 10.5 and 10.6, which includes faster computation, more accurate EM models, and extensions to the validation suite. New approaches are developed to simulate radiation damage for silicon vertex detectors and for configuration of multiple scattering per detector region. Improvements in user interfaces developed for low-energy and the Geant4-DNA project are used also for LHC simulation optimisation.

Monte Carlo simulation for proton dosimetry in magnetic fields: Fano test and magnetic field correction factors k B for Farmer-type ionization chambers

“…Furthermore, several transport parameters can be set or tuned depending on the specific requirements of the simulation. For example, the recommended g4em- standard_opt4 physics list in TOPAS, corresponding to G4EMStandardPhysics_option4 7 in Geant4, is used to define the electromagnetic processes, models and its parameters for all particles with settings which are appropriate for radiotherapy with photons and charged particle beams (Ivanchenko et al 2020). For photons, the pair production is handled by the BetheHeitler5D model, the Compton scattering by the G4LowEPComptonModel (<20 MeV) and both the photo-electric effect and the Rayleigh scattering by the Livermore models.…”

Gamma-Ray Polarimetry

“…The Geant4 simulation library (Agostinelli et al, 2003) accurately simulates polarized Compton scattering and can be used to derive the necessary response files, provided a sufficiently accurate mass model is implemented. For pair conversion, after it was found (Gros and Bernard, 2017b) that the existing polarized "Physics Model" fails to generate events with the known polarization asymmetry (Gros and Bernard, 2017a), a new "G4BetheHeitler5DModel" Physics Model (Bernard, 2018;Semeniouk and Bernard, 2019) that samples the 5D polar-ized Bethe-Heitler differential cross section (May, 1951) has been implemented and has been available since Geant4 release 10.6 (Ivanchenko et al, 2020).…”