Low Energy electromagnetic Physics - Monash


Describes the process of unpolarised photons Compton scattering off atomic bound electrons in the relativistic impulse approximation. The model was developed as an alterative to Compton scattering models developed from Ribberfors' Compton scattering framework (link), i.e. G4LivermoreComptonModel and G4PenelopeComptonModel, to improve the accuracy of Compton electron ejection direction algorithms below 5 MeV. G4LowEPComptonModel utilises a special-relativistic formalism and the conservation of energy and momentum to compute:

  • energy and angular distributions of Compton scattered photons off non-stationary atomic bound electrons,
  • and energy and ejected angular distributions of Compton electrons.

A version for polarized gammas is also available: G4LowEPPolarizedComptonModel.


How to use the model in Geant4 user physics lists

The model can be used as follows:


      G4PhysicsListHelper* ph = G4PhysicsListHelper::GetPhysicsListHelper();
      G4ComptonScattering* cs = new G4ComptonScattering;
      G4VEmModel* theLowEPComptonModel = new G4LowEPComptonModel();
      cs->AddEmModel(0, theLowEPComptonModel);
      ph->RegisterProcess(cs, particle);


Physics builders

G4LowEPComptonModel is added to the electromagnetic physics constructor "G4EmStandard_option4" constructed from the most accurate models from standard / low energy electromagnetic physics groups.


Availability and documentation

You may check the following publication: A low energy bound atomic electron Compton scattering model for Geant4, J. M. C. Brown et al., Nucl. Instrum. and Meth. B 338 (2014) 77-88 (link)

Address any additional queries to jeremy.brown@cern.ch.