Summary

The implemented physics models are meant to match the defaults constructed in G4EmStandardPhysics. Known differences are:

• Particles other than electrons, positrons, and gammas are not currently supported.

• As with the AdePT project, Celeritas currently extends the range of Urban MSC to higher energies rather than implementing the Wentzel-VI and discrete Coulomb scattering.

• Celeritas imports tracking cutoffs and other parameters from G4EmParameters, but some custom model cutoffs are not accessible to Celeritas.

The following table summarizes the EM processes and models in Celeritas.

Electromagnetic physics processes and models available in Celeritas.

Particle	Processes	Models	Celeritas Implementation	Applicability
\(e^-\)	Ionization	Møller	celeritas::MollerBhabhaInteractor	0–100 TeV
	Bremsstrahlung	Seltzer–Berger	celeritas::SeltzerBergerInteractor	0–1 GeV
		Relativistic	celeritas::RelativisticBremInteractor	1 GeV – 100 TeV
	Coulomb scattering	Urban	celeritas::UrbanMscScatter	100 eV – 100 TeV
		Coulomb	celeritas::CoulombScatteringInteractor	0–100 TeV
\(e^+\)	Ionization	Bhabha	celeritas::MollerBhabhaInteractor	0–100 TeV
	Bremsstrahlung	Seltzer-Berger	celeritas::SeltzerBergerInteractor	0–1 GeV
		Relativistic	celeritas::RelativisticBremInteractor	1 GeV – 100 TeV
	Coulomb scattering	Urban	celeritas::UrbanMscScatter	100 eV – 100 TeV
		Coulomb	celeritas::CoulombScatteringInteractor	0–100 TeV
	Annihilation	\(e^+,e^- \to 2\gamma\)	celeritas::EPlusGGInteractor	0–100 TeV
\(\gamma\)	Photoelectric	Livermore	celeritas::LivermorePEInteractor	0–100 TeV
	Compton scattering	Klein–Nishina	celeritas::KleinNishinaInteractor	0–100 TeV
	Pair production	Bethe–Heitler	celeritas::BetheHeitlerInteractor	0–100 TeV
	Rayleigh scattering	Livermore	celeritas::RayleighInteractor	0–100 TeV
\(\mu^-\)	Ionization	ICRU73QO	celeritas::MuHadIonizationInteractor	0–200 keV
		Bethe–Bloch	celeritas::MuHadIonizationInteractor	200 keV–1 GeV
		Mu Bethe–Bloch	celeritas::MuHadIonizationInteractor	200 keV–100 TeV
	Bremsstrahlung	Mu bremsstrahlung	celeritas::MuBremsstrahlungInteractor	0–100 TeV
	Pair production	Mu pair production	celeritas::MuPairProductionInteractor	0.85 GeV–100 TeV
\(\mu^+\)	Ionization	Bragg	celeritas::MuHadIonizationInteractor	0–200 keV
		Bethe–Bloch	celeritas::MuHadIonizationInteractor	200 keV–1 GeV
		Mu Bethe–Bloch	celeritas::MuHadIonizationInteractor	200 keV–100 TeV
	Bremsstrahlung	Mu bremsstrahlung	celeritas::MuBremsstrahlungInteractor	0–100 TeV
	Pair production	Mu pair production	celeritas::MuPairProductionInteractor	0.85 GeV–100 TeV