FTFP_BERT Physics List

It is the current Geant4 default [JA16].

Hadronic Component

The purely hadronic part of this physics list consists of elastic, inelastic, capture and fission processes. Each process is built from a set of cross section sets and interaction models which provide the detailed physics implementation.

Inelastic models

The inelastic hadron-nucleus processes are implemented by the FTF, Bertini and Precompound models. The Bertini intranuclear cascade is responsible for \(\pi ^+,\ \pi ^-,\ K^+,\ K^-,\ K_L,\ K_S,\ \Lambda ,\ \Sigma ^+,\ \Sigma ^-,\ \Sigma ^0,\ \Xi ^-,\ \Xi ^0\) and \(\Omega ^-\) interactions between 0 to 12 GeV. The Fritiof parton model (FTF) handles these same particles, but over the range 3 GeV to 100 TeV. It also handles anti-protons, anti-neutrons, anti-deuterons, anti-tritons, anti-3He and anti-alphas from 0 to 100 TeV/n.

Where Bertini and FTF overlap in particle type and energy range, Bertini is invoked with a probability that decreases linearly from 1.0 at 3 GeV to 0.0 and 12 GeV, and FTF is invoked with the complementary probability.

When the FTF model is used, the Precompound model (P) is also invoked to de-excite the remnant nucleus after the initial high energy interaction. The precompound model in turn calls the Fermi breakup, multi-fragmentation, neutron evaporation and photon evaporation models as needed. When the Bertini model is used, its own, simpler precompound and de-exciation models are invoked.

Inelastic nucleus-nucleus scattering for all incident A is handled by the Binary Light Ion Cascade (BIC) between 0 and 4 GeV/n, and by the FTF model between 2 GeV/n and 100 TeV/n. The scheme for choosing models in overlapping energy regions is the same as that for FTFP and BERT.

The hadronic interaction of gammas is handled by the photo-nuclear process in which gammas below 3.5 GeV are interacted using the Bertini cascade, and above 3 GeV by the Quark-gluon String (QGS) model. Muons, electrons and positrons alos interact via transfer of virtual photons. These interactions are handled by G4MuonVDNuclearModel and G4ElectroVDNuclearModel which are applied at all energies.

Inelastic cross sections

The following cross section sets are used for pions and kaons below 91 GeV: G4PiNuclearCrossSection for \(\pi ^+\) and \(\pi ^-\), G4ChipsKaonPlusInelasticXS for \(K^+\), G4ChipsKaonMinusInelasticXS for \(K^-\) and G4ChipsKaonZeroInelasticXS for \(K^0\). For all these the Barashenkov-Glauber cross sections are used at 91 GeV and above.

G4BGGNucleonInelasticXS is used for protons and neutrons. Below 91 GeV, this class uses the Barashenkov parameterization and above 91 GeV it uses the Glauber-Gribov cross sections. For \(\lambda,\ \Sigma,\ \Xi \) and \(\Omega ^-\) hyperons the G4ChipsHyperonInelasticXS set is used at all energies.

All nucleus-nucleus cross sections are provided by G4ComponentGGNuclNuclXsc at all projectile energies. This class is the Glauber-Gribov nucleus-nucleus cross section parameterization. When the projectile is an anti-proton, anti-neutron, anti-deuteron, anti-triton, anti-3He or anti-alpha, the G4ComponentAntiNuclNuclearXS class provides the cross sections using the Glauber-Gribov parameterization.

Hadronic gamma interaction cross sections are supplied by G4PhotoNuclearCrossSection which is used at all gamma energies. G4ElectroNuclearCrossSection is used at all energies for \(e ^+\) and \(e ^-\), while G4KokoulinMuonNuclearXS is used for \(\mu ^+\) and \(\mu ^-\) at all energies.

Elastic models

Elastic scattering of protons and neutrons use G4ChipsElasticModel from 0 to 100 TeV. This model uses the Kossov parameterized cross sections.

For almost all other hadrons the G4HadronElastic model is used for some or all of the energy range. This model is a two-exponential momentum transfer model updated from the old Gheisha code. It is used at all energies by kaons, hyperons, deuterons, tritons, \(^3\)He, alphas and anti-neutrons.

Elastic \(\pi ^+\) and \(\pi ^-\) scattering is implemented by G4HadronElastic model from 0 1o 1 GeV and by the G4ElasticHadrNucleusHE coherent scattering model from 1 GeV and up.

For anti-protons, anti-deuterons, anti-tritons, anti-3He and anti-alphas, G4HadronElastic is used from 0 to 100 MeV/n. Above 100 MeV/n these particles are handled by the G4AntiNuclElastic model.

There is currently no elastic scattering model for nuclear projectiles with \(A > 4\).

Elastic cross sections

From 0 to 100 TeV ChipsProtonElasticXS provides the proton cross sections while G4NeutronElasticXS provides the neutron cross sections.

G4BGGPionElasticXS supplies the \(\pi ^+\) and \(\pi ^-\) cross sections using the Barashenkov parameterization below 91 GeV and the Glauber-Gribov cross sections above 91 GeV. Kaons use the Glauber-Gribov cross sections at all energies.

Hyperons and anti-neutrons use the Gheisha elastic cross sections at all energies.

anti-p, anti-d, anti-t, anti-3He and anti-alpha use the Glauber model cross section in G4ComponentAntiNuclNuclearXS at all energies.

The Gheisha elastic cross sections are used for d,t and alpha at all energies while for 3He the Glauber-Gribov elastic cross sections are used at all energies.

No elastic cross sections are available for projectiles with \(A > 4\).

Capture and stopping

The capture of negative pions and kaons once they have stopped is handled by the BertiniCaptureAtRest model which uses the Bertini cascade. The capture of anti-p, anti-d, anti-t, anti-3He, anti-alpha is handled by the FritiofCaptureAtRest model which uses the Fritiof string model.

Neutron capture uses the G4NeutronRadCapture model with the G4NeutronCaptureXS cross sections.

Electromagnetic Component

This physics list uses “standard” Geant4 electromagnetic physics as built by the G4EmStandardPhysics constructor EM physics constructors. It is implemented for the following particles: \( \gamma ,\ e^-,\ e^+,\ \mu ^-,\ \mu ^+,\ \tau ^-,\ \tau ^+,\) \(K^+,\ K^-,\ p,\ \Sigma ^+,\ \Sigma ^-,\ \Xi ^-,\ \Omega ^-,\) anti( \(\Sigma ^+,\ \Sigma ^-,\ \Xi ^-,\ \Omega ^-\)), \(d,\ t,\ ^3He,\ \alpha,\) anti( \(d,\ t,\ ^3He,\ \alpha \)), and G4GenericIon. Several charmed mesons are also treated, \( D^+,\ D^-,\ D_s^+,\ D_s^-,\ \Lambda_c^+,\ \Sigma_c^+,\ \Sigma_c^{++},\ \Xi_c^+,\) anti(\(\Lambda _c^+,\ \Sigma _c^+,\ \Sigma _c^{++},\ \Xi_c^+\)), as well as two bottom mesons, \(B^+\) and \(B^-\).

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 Standard EM models implement several processes.

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 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. 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.

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 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 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 BetheBloch 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. Mulitiple Coulomb scattering in implemented by the Urban model at all energies. For alphas Bragg ionization is performed below 7.9 MeV and BetheBloch ionization above. For generic ions, Bragg is used below 2 MeV and BetheBloch above.

There is no treatment of optical photons in this physics list.

Decay Component

The decay of all long-lived hadrons and leptons is handled by the G4Decay process. It does not handle the decay of hadronic resonances like deltas, which should be decaied within hadronic models and heavy-flavor particles like D and B mesons or charmed hyperons.

Muon capture or decay at rest is handled by the G4MuonMinusCapture process.

Neutron tracking cut

Neutrons may be killed by energy cut (zero by default) or by time cut (10 microsecond by default). These cuts may be modified via UI commands.