EM Opt3

This physics list uses “standard” Geant4 electromagnetic physics as built by the G4EmStandardPhysics_option3 constructor.

Processes cover physics from 0 to 100 TeV for gamma, \(e^-\) and \(e^+\) and up to 1 PeV for muons. EM interactions of charged hadrons and ions cover the range 0 to 100 TeV. Though the operational energy range goes down to zero, below 1 keV accuracy of these models is substantially lower.

For each particle type several processes are implemented. Photons: \(e^-/e^+\) pair production is implemented by the BetheHeitler model with the LPM effect at high energies and Compton scattering is implemented by the Klein-Nishina model. Photo-electric effect and Rayleigh scattering are both handled by the Livermore models.

Electrons and positrons: multiple Coulomb scattering is handled by the Urban model from 0 to 100 TeV. UseDistanceToBoundary step limitation is used for multiple scattering. Bremsstrahlung is implemented by the eBremSB model and the eBremLPM model which takes into account the LPM effect at high energies. Ionisation is modelled by the Moller-Bhabha formulation, and positron annihilation is implemented by the eplus2gg model.

Muons: multiple Coulomb scattering is handled by the the Urban model from 0 to 100 TeV. Bremsstrahlung is handled by the MuBrem model. Ionisation is implemented by several models depending on energy and particle type. From 0 to 200 keV, the Bragg model is used for \(\mu ^+\) and the ICRU73Q0 parameterisation is used for \(\mu ^-\). Between 200 keV and 1 GeV the BetheBloch model is used for both \(\mu ^+\) and \(\mu ^-\), and from 1 GeV to 100 TeV, the MuBetheBloch model is used for both \(\mu ^+\) and \(\mu ^-\). The muPairProduction model handles e+/e- pair production caused by either \(\mu ^+\) or \(\mu ^-\).

Pions, kaons, protons and anti-protons: multiple Coulomb scattering is performed by the Urban model and Coulomb scattering by the eCoulombScattering model. Bremsstrahlung is handled by hBrem model. \(e^-/e^+\) pair production by hadrons is implemented by the hPairProduction model. Ionisation is handled by several models depending on energy and particle type. For pions below 298 keV, Bragg model ionisation is used for \(\pi ^+\), and the ICRU73Q0 parameterisation is used for \(\pi ^-\). Above this energy BetheBloch ionisation is used. For kaons, the same ionisation models are used, but the change from low energy to high energy models occurs at 1.05 MeV. For protons, the Bragg model is used below 2 MeV and the BetheBloch above. For anti-protons ICRU73Q0 is used below 2 MeV and BetheBloch above.

alpha and G4GenericIon: only two EM processes are applied. Multiple Coulomb scattering in implemented by the Urban model at all energies. For alphas Bragg ionisation is performed below 7.9 MeV and BetheBloch ionisation above. For generic ions, Bragg is used below 2 MeV/u and BetheBloch above. Nuclear stopping model is used below 1 MeV.