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11. Physics List#

G4SEE Physics list is a Modular Physics list, which can be build up from different (e.g. EM, elastic hadronic, inelastic hadronic, etc.) physics modules.

Physics modules are sets of physics models implemented for different particle processes (interactions).

One can add these physics modules listed below via the /SEE/physics/addPhysics macro command.

Please note that the running time (or CPU time) of G4 strongly depends on the physics modules used. One can sacrifice some accuracy and precision in order to improve the performance and run the simulation faster and vica versa.

11.1. Particles#

By default, all the particles of the Standard Model are defined in G4SEE (including short-lived, exotic particles and antiparticles).

Geant4 naming convention is applicable everywhere, where particles could be defined or referenced.

Ions heavier than alpha are Generic Ion particles.

11.2. Electromagnetic physics#

One of the EM modules (listed below) is mandatory and only one can be used for a run.

  • G4EmStandardPhysics_option4 - DEFAULT, RECOMMENDED (added and used by default, no need to add)

  • G4EmStandardPhysics_option3

    • (was) used for medical and space applications, accurate, but not as accurate as EM Opt4

    • G4 doc / EM Opt3

  • G4EmStandardPhysics_option2 - Do not use!

    • for HEP (calorimeters), fast but not precise, nor accurate, used by LHCb

  • G4EmStandardPhysics_option1 - Do not use!

    • for HEP (calorimeters), fast but not precise, nor accurate, used by CMS

  • G4EmStandardPhysics_option - Do not use!

    • used by ATLAS

  • G4EmPenelopePhysics

    • Specific low-energy Penelope models are used for \(\gamma\), \(e^{\pm}\) between 250 eV and 1 GeV energy

    • Above 1 GeV and for all other charged particle, it is the same as the EM Opt4

  • G4EmLivermorePhysics

  • G4MicroElecPhysics - EXPERIMENTAL (not recommended yet)

    • Low-energy microdosimetry for Silicon only, >16.7 eV energy

    • This module is limited to the Sensitive volume only

    • Extremely CPU time-consuming

11.3. Hadronic physics#

XS = Cross-Section; FS = Final State

11.3.1. Elastic#

Elastic physics modules for hadrons. Only one can be chosen from the elastic modules denoted by (*).

  • G4HadronElasticPhysics (*)

    • Hadron nuclear elastic process for all hadrons except for GenericIon

    • proton: Barashenkov-Glauber-Gribov XS; Chips FS

    • neutron: G4NeutronElasticXS; Chips FS

  • G4HadronElasticPhysicsHP (*) - recommended for neutrons

    • Same as G4HadronElasticPhysics, but for neutron < 20 MeV: NeutronHP XS & FS

  • G4HadronDElasticPhysics (*)

    • Hadron nuclear elastic process for all hadrons except for GenericIon

    • proton: Barashenkov-Glauber-Gribov XS; Diffuse model FS where applicable, else Gheisha

    • neutron: G4NeutronElasticXS; Diffuse model FS where applicable, else Gheisha

  • G4HadronHElasticPhysics (*)

    • Hadron nuclear elastic process for all hadrons except for GenericIon

    • proton: Barashenkov-Glauber-Gribov XS; Diffuse model FS (except for Hydrogen where Chips is used)

    • neutron: G4NeutronElasticXS; Diffuse model FS (except for Hydrogen where Chips is used)

  • G4IonElasticPhysics - recommended for heavy ions

    • Elastic process only for GenericIon: Glauber-Gribov XS and Diffuse model FS

  • G4ThermalNeutrons - recommended for thermal neutrons

    • High Precision thermal scattering model, only for neutron < 4 eV

    • Based on thermal scattering data of evaluated nuclear data libraries (ENDF/B-VI, Release 2)

    • Materials (elements): TS_Aluminium_Metal (Al), TS_Beryllium_Metal (Be), TS_Iron_Metal (Fe), G4_BERYLLIUM_OXIDE (Be, O), G4_GRAPHITE (C), G4_POLYETHYLENE (H), G4_URANIUM_OXIDE (U, O), G4_WATER (H) (only the relevant ones are listed here)

    • Should be added as the last (elastic, inelastic) hadronic physics module, since it overwrites any previously added neutron model between 0-4 eV

11.3.2. Inelastic#

Inelastic physics modules are combinations of several models applicable on different energy ranges. The major models are:

  • QGS: Quark-Gluon string models (>15 GeV)

  • FTF: Fritiof Parton model (>5 GeV)

  • BIC: Binary Cascade model (<10 GeV)

  • BERT: Bertini Intranuclear Cascade model (<10 GeV)

  • INCLXX: Liège Intranuclear Cascade model (<10 GeV)

  • P: Precompound/de-excitation model

  • HP: High Precision neutron model (<20 MeV)

Inelastic physics modules have a specific naming convention, indicating the consisting sub-modules: <String(s)>_<PreComp>_<Cascade>_<Neutron>. The same naming convention is also used by the Reference (pre-packaged) Physics lists (not applicable to G4SEE).

It is not trivial which one to use and there is no best option to choose in general. It is heavily depends on the actual simulation case or study. It is strongly recommended to run the simulation several times adding different inelastic modules for comparison. In most cases, they result the same or very similar distribution, but there could be a discrepancy in the higher energy range of the \(E_{dep}\) distribution (hadronic tail).

Modules containing HP neutron model (their names ending with HP) are recommended for neutrons.

Only one can be chosen from the inelastic modules listed below. All of them are optional.

  • G4HadronInelasticQBBC

    • Recommended for accurate simulation of low-energy transport of protons and neutrons. Best agreement below 1 GeV for thin target experiments, It is also recommended for medical and space applications

    • For higher energies it is the same as the FTFP_BERT

    • G4 doc / QBBC (inelastic part only)

  • G4HadronPhysicsFTFP_BERT

    • Recommended for cosmic rays where good treatment of very high energy particles is required, but only below 10 TeV

    • Recommended for collider physics applications, best agreement with test beam calorimeter data, including shower shape, energy response and resolution

    • G4 doc / FTFP_BERT (inelastic part only)

  • G4HadronPhysicsFTFP_BERT_HP

  • G4HadronPhysicsFTFP_BERT_ATL

  • G4HadronPhysicsFTFQGSP_BERT

  • G4HadronPhysicsFTF_BIC

  • G4HadronPhysicsINCLXX

  • G4HadronPhysicsQGSP_BERT

  • G4HadronPhysicsQGSP_BERT_HP

  • G4HadronPhysicsQGS_BIC

  • G4HadronPhysicsQGSP_BIC

  • G4HadronPhysicsQGSP_BIC_HP

  • G4HadronPhysicsQGSP_FTFP_BERT

11.3.3. Ion Inelastic#

Inelastic ion-ion processes for deuteron, triton, He3, alpha and GenericIon projectiles. Only one can be chosen from the ion inelastic modules listed below. All of them are optional.

  • G4IonPhysics

    • With Glauber-Gribov XS and Binary Light Ion (BIC, with Precompound/de-excitation) and FTFP (Fritiof string model with Precompound/de-excitation) for the final state. BIC is used for projectiles of kinetic energies below 6 GeV/nucleon, and FTF above 3 GeV/nucleon.

  • G4IonQMDPhysics

    • With Glauber-Gribov XS and BIC, QMD and FTFP for the final state. These three final-state models are used in the following intervals of projectile kinetic energy: BIC below 110 MeV/nucleon, QMD between 100 and 10 000 MeV/nucleon, and FTF above 9990 MeV/nucleon.

  • G4IonINCLXXPhysics

    • With Glauber-Gribov XS and INCLXX and FTFP for the final state. INCLXX is used below 3 GeV/nucleon, and FTF above 2.9 GeV/nucleon.

11.4. Decay physics#

Decay processes of unstable particles

  • G4DecayPhysics - DEFAULT, MANDATORY (used by default and can not be removed)

  • G4RadioactiveDecayPhysics (optional)

11.5. Transportation#

  • Transportation - DEFAULT, MANDATORY (used by default and can not be removed)