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 BetheHeitler5D model with the LPM effect at high energies. The Compton scattering is implemented above 20 MeV by the Klein-Nishina model with Doppler broading effect taken into account. Below 20 MeV the Monarsh University model (G4LowEPComptonModel) for Compton scattering. 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. The value of the Range Factor is 0.08. 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 above 100 keV and using Penelope model below. 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. 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 \(\mu ^-\).

Above 200 keV and 1 GeV 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. 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 Bethe-Bloch 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: three EM processes are applied. Multiple Coulomb scattering in implemented by the Urban model at all energies. For ionisation below 2 MeV/u data are used. Priority of data is following: ICRU90, ICRU73, PSTAR, ASTAR, ICRU49. The ICRU90 data for the stopping powers of protons, alpha, and ions are available for water, graphite, and air targets. Other data have less accuracy but are applicable for more combinations of projectile ion and target element/material. Above 2 MeV/u the Bethe-Bloch model is used for alpha and Lindhard-Sorensen model for ions. Nuclear stopping model is used below 1 MeV.