Introduction to Gamma Processes

All processes of gamma interaction with media in Geant4 happen at the end of the step, so these interactions are discrete and corresponding processes are following the G4VDiscreteProcess interface.

General Interfaces

There are a number of similar functions for discrete electromagnetic processes and for electromagnetic (EM) packages an additional base classes were designed to provide common computations [eal09]. Common calculations for discrete EM processes are performed in the class G4VEmProcess. Derived classes (Table 1) are concrete processes providing initialisation. The physics models are implemented using the G4VEmModel interface. Each process may have one or many models defined to be active over a given energy range and set of G4Regions. Models are implementing computation of energy loss, cross section and sampling of final state. The list of EM processes and models for gamma incident is shown in Table 1.

Table 1 List of process and model classes for gamma.

EM process	EM model	Ref.
G4PhotoElectricEffect	G4PEEffectFluoModel	PhotoElectric Effect
	G4LivermorePhotoElectricModel	Livermore Model
	G4LivermorePolarizedPhotoElectricModel
	G4PenelopePhotoElectricModel	Penelope Model
G4PolarizedPhotoElectricEffect	G4PolarizedPEEffectModel	Polarized Photoelectric Effect
G4ComptonScattering	G4KleinNishinaCompton	Compton scattering
	G4KleinNishinaModel	Compton scattering
	G4LivermoreComptonModel	Livermore Model
	G4LivermoreComptonModelRC
	G4LivermorePolarizedComptonModel	Polarized Compton scattering
	G4LowEPComptonModel	Monash University Low Energy Model
	G4PenelopeComptonModel	Penelope Model
G4PolarizedCompton	G4PolarizedComptonModel	Polarized Compton scattering
G4GammaConversion	G4BetheHeitlerModel	Gamma Conversion into e+e- Pair
	G4BetheHeitler5DModel	Five-dimensional (5D) Bethe-Heitler gamma Conversion to e+e-
	G4BetheHeitler5DModel	Pair production by Linearly Polarized Gamma Rays - Five-dimensional (5D) Bethe-Heitler Model
	G4PairProductionRelModel
	G4LivermoreGammaConversionModel	Livermore Model
	G4BoldyshevTripletModel	Livermore Triple Gamma Conversion
	G4LivermoreNuclearGammaConversionModel
	G4LivermorePolarizedGammaConversionModel
	G4PenelopeGammaConversion	Penelope Model
G4PolarizedGammaConversion	G4PolarizedGammaConversionModel	Polarized Gamma conversion into an electron–positron pair
G4RayleighScattering	G4LivermoreRayleighModel	Livermore Model
	G4LivermorePolarizedRayleighModel
	G4PenelopeRayleighModel	Penelope Model
G4JAEAElasticScattering	G4JAEAElasticScatteringModel	JAEA Elastic Scattering Model
G4GammaConversionToMuons		Gamma Conversion into Pair

Bibliography

eal09(1,2)

J. Apostolakis et al. Geometry and physics of the geant4 toolkit for high and medium energy applications. Radiation Physics and Chemistry, 78(10):859–873, oct 2009. URL: https://doi.org/10.1016/j.radphyschem.2009.04.026, doi:10.1016/j.radphyschem.2009.04.026.