EM Opt4

This physics list uses “standard” Geant4 electromagnetic physics as built by the G4EmStandardPhysics_option4 constructor.

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 above 20 MeV. Below 20 MeV the Monarsh University model (G4LowEPComptonModel) for Compton scattering and Penelope pair production models are used. Photo-electric effect and Rayleigh scattering are both handled by the Livermore models.

Electrons and positrons: multiple Coulomb scattering is handled by the Goudsmit-Sounderson model from 0 to 100 MeV and by the WentzelVI model from 100 MeV to 100 TeV, which is combined with the single Coulomb scattering model, which is applied for large angle scattering. UseSafetyPlus step limitation with error free approach near geometry boundaries 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. Ionization is modeled by the Moller-Bhabha formulation, and positron annihilation is implemented by the eplus2gg model. The process of \(e^-/e^+\) pair production by electrons and positrons is also used.

Muons: multiple Coulomb scattering is handled by the WentzelVI model combined with the single scattering model at all energies, and by the eCoulombScattering model at all energies. Bremsstrahlung is handled by the MuBrem model. Ionization 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 parameterization is used for \(\mu ^-\). Between 200 keV and 1 GeV the Bethe-Bloch 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 WentzelVI 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. Ionization is handled by several models depending on energy and particle type. For pions below 298 keV, Bragg model ionization is used for \(\pi ^+\), and the ICRU73Q0 parameterization is used for \(\pi ^-\). Above this energy Bethe-Bloch ionization is used. For kaons, the same ionization 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 ionization is performed below 7.9 MeV and Bethe-Bloch ionization above. For generic ions, For ion ionisation of ions below 1 GeV/u ICRU73 model (G4IonParametrisedLossModel) is used, above 1 GeV/u the Bethe-Bloch model is applied. Nuclear stopping model is used below 1 MeV.