Physics Lists EM constructors in Geant4 10.3

Default

emstandard The default EM constructor is used in major part of reference Physics Lists (FTFP_BERT, FTF_BIC, QGSP_FTFP_BERT, QGSP_BIC, ...):
- G4UrbanMscModel for multiple scattering of e+ and e- below 100 MeV;
- G4WentzelVIModel for multiple scattering of combined with G4eCoulombScatteringModel for large angle scattering for muons, pions, kaions, protons, and anti-protons at all enegries, for e+ and e- above 100 MeV;
- G4UrbanMscModel for all other chaged particles.

Option 1

emstandard_opt1 is designed for HEP productions (CMS focused), it is used in the FTFP_BERT_EMV, QGSP_BERT_EMV, QGSP_BERT_EML, LHEP_EMV reference Physics Lists. The corresponding physics constructor includes following modifications for electron and positron transport with respect to the default EM physics:
- the option "fMinimal" is used for multiple scattering step limitation, which provides accuracy and CPU performance similar to that of the Geant4 version 7.1p02;
- the parameter dRoverRange used in computation of step limit by the ionisation process is set to the value 0.8.
- the ApplyCuts option is enabling production thresholds (cuts) on secondary particles for all EM processes including photoelectric effect, Compton scattering, gamma conversion, positron annihilation.

Option 2

emstandard_opt2 is designed for HEP productions (LHCb focused), it is used in the FTFP_BERT_EMX and QGSP_BERT_EMX reference Physics Lists. The corresponding physics constructor includes following modifications for electron and positron transport with respect to the default EM physics:
- the option "fMinimal" is used for multiple scattering step limitation, which provides accuracy and CPU performance similar to that of the Geant4 version 7.1p02;
- the parameter dRoverRange used in computation of step limit by the ionisation process is set to the value 0.8.
- Alternative G4Generator2BS angular generator is used for the bremsstrahlung process.

Option 3

emstandard_opt3 designed for any applications required higher accuracy of electrons, hadrons and ion tracking without magnetic field. It is used in extended electromagnetic examples and in the QGSP_BIC_EMY reference Physics List. The corresponding physics constructor includes following modifications:
- G4UrbanMscModel for multiple scattering of all charged particles;
- the option "fUseDistanceToBoundary" for multiple scattering of electrons and positrons;
- accurate algorithm of sampling of lateral displacement is enabled;
- increased number of bins in physics tables - 220 (84 bins by default), start all tables from 10 eV;
- the parameter dRoverRange used in computation of step limit by the ionisation process is reduced with respect to the default value 0.2: 0.1 for alpha, He3, ions;
- the parameter finalRange used in computation of step limit by the ionisation process is reduced with respect to the default value 1 mm: for e+,e- is 0.1 mm, for muons, pions, proton is 0.05 mm, for alpha and He3 0.01 mm, for ions 0.001 mm;
- G4KleinNishinaModel is used for the Compton scattering simulation which include Doppler broading and allowing to simulate atomic deexcitation;
- G4IonParametrisedLossModel is used for ion ionisation, this model is based on ICRU73 ion stopping data;
- angular generator G4Generator2BS is used for bremsstrahlung;
- G4RayleighScattering process is used with the default Livermore Rayleigh scattering model;
- Fluorescence is enabled by default.
- G4NuclearStopping process is used for alpha, He3, ions.

Option 4

emstandard_opt4 new physics constructor was designed for any applications required higher accuracy of electrons, hadrons and ion tracking. Use the most accurate standard and low-energy models. It is used in extended electromagnetic examples and in the QGSP_BIC_EMZ reference Physics List. The corresponding physics constructor includes following modifications with the G4EmStandardPhysics_option3.cc:
- G4KleinNishinaModel is used above 20 MeV, G4LowEPComptonModel is used below for the Compton scattering simulation. Both models provide simulation of Doppler broading and atomic deexcitation.
- G4PenelopeGammaConversion model is used for gamma conversion below 1 GeV;
- the parameter RangeFactor for multiple scattering of e+, e- is set to 0.01 (the default 0.04);
- for e+ and e- in G4UrbanMscModel an accurate algorithm of sampling of lateral displacement is enabled;

GoudsmitSaunderson

emstandardGS physics constructor for validation of updated Goudsmit-Saunderson model of multiple scattering. The corresponding physics constructor includes following modifications on top of G4EmStandardPhysics.cc:
- G4GoudsmitSoundersonMscModel for multiple scattering of electrons and positrons below 100 MeV.

WentzelVI

emstandardWVI new physics constructor for validation of combined WentzelVI and Single Scattering models. The corresponding physics constructor includes following modifications on top of G4EmStandardPhysics.cc:
- G4WentzelVIModel for multiple scattering combined with G4eCoulombScatteringModel for large angle scattering is used for electrons, positrons, muons, pions, kaons, protons, and anti-protons.

Single scattering

emstandardSS new physics constructor for validation of Single Scattering models. The corresponding physics constructor includes following modifications on top of G4EmStandardPhysics.cc:
- G4eCoulombScatteringModel for simulation of scattering for electrons, positrons, muons, pions, kaons, protons, and anti-protons;
- G4eSingleCoulombScatteringModel for simulation of scattering for electrons if a flag of Mott corrections is enabled;
- G4IonCoulombScatteringModel for simulation of scattering of ions.

Livermore

emlivermore designed for any applications required higher accuracy of electrons, hadrons and ion tracking without magnetic field. It is used in extended electromagnetic examples. The corresponding physics constructor includes following modifications compared with the G4EmStandardPhysics_option4.cc:
- G4LivermorePhotoElectricModel for gamma below 1 GeV;
- G4LivermoreComptonModel for gamma below 1 GeV;
- G4LivermoreGammaConversionModel for gamma below 1 GeV;
- G4LivermoreIonisationModel for e- below 100 keV;
- G4LivermoreBremsstrahlungModel for e- below 1 GeV with angular generator G4Generator2BS.

Livermore with polarisation

emlivermore_polar designed for any applications required higher accuracy of electrons, hadrons and ion tracking without magnetic field. It is used in extended electromagnetic examples. The corresponding physics constructor includes following modifications compared with the G4EmLivermorePhysics.cc:
- G4LivermorePolarizedPhotoElectricModel for gamma below 1 GeV;
- G4LivermorePolarizedComptonModel for gamma below 1 GeV;
- G4LivermorePolarizedGammaConversionModel for gamma below 1 GeV;
- G4LivermorePolarizedRayleighModel for gamma below 1 GeV;
- G4LivermoreIonisationModel for e- below 100 keV;
- G4LivermoreBremsstrahlungModel for e- below 1 GeV with angular generator G4Generator2BS.

Penelope

empenelope designed for any applications required higher accuracy of electrons, hadrons and ion tracking without magnetic field. It is used in extended electromagnetic examples. The corresponding physics constructor includes following modifications compared with the G4EmStandardPhysics_option4.cc:
- G4PenelopePhotoElectricModel for gamma below 1 GeV;
- G4PenelopeComptonModel for gamma below 1 GeV;
- G4PenelopeGammaConversionModel for gamma below 1 GeV;
- G4PenelopeRayleighModel for gamma below 1 GeV;
- G4PenelopeIonisationModel for e+ and e- below 1 GeV;
- G4PenelopeBremsstrahlungModel for e+ and e- below 1 GeV.

Low-energy

emlowenergy designed on top of Livermore physics for validation of new low-energy models. It is used in extended electromagnetic examples. The corresponding physics constructor includes following modifications compared with the G4EmLivermorePhysics.cc:
- G4LowEWentzelVIModel for multiple scattering of electrons and positrons;
- G4LowEPComptonModel below 20 MeV;
- G4SeltzerBergerModel for e+, e- bremsstrahlung below 1 GeV; angular generator G4Generator2BS.

DNA physics

emDNAphysics designed for any applications required higher accuracy of electrons, hadrons and ion tracking without magnetic field. It is used in extended electromagnetic examples. The corresponding physics constructor includes very low-energy processes for simulation of particle transport in liquid water. In the same directory there are alternative physics constructors G4EmDNAPhysics_optionX, where X varies from 1 to 7. See more detail in Geant4-DNA pages.

Physics Lists per G4Region

EM physics configuration per G4Region is a new feature designed for combination of physics configurations for different geometry regions. This is needed in order to have more accurate or less accurate simulation in a specific sub-detector. Other use case is to combine standard and DNA models, where the last are available so far only for liquid water and few other materials. The configuration may be done at G4PreInit_State via UI commands. The list of UI commands for such configuration is following:
here myregion is the name of G4Region, EMtype is the name of EM physics constructor (for example, G4EmStandard_Opt3).

High Enegry Processes

High energy processes with low cross sections are needed for FCC design studies. These processes may be now enabled/disabled on top of any reference Physics List using UI commands:

Physics Lists of Geant4 examples

TestEm7 extended/electromagnetic example providing several variants of EM physics, which are also used in other Geant4 applications. This example can be recommended as a starting point for user customized Physics List.

It is shown how to add G4BraggIonGasModel and G4BetheBlochIonGasModel on top of standard ionisation models using UI command "/testem/phys/addPhysics ionGasModels", which enables models via G4EmConfigurator; these model allowing to simulate ion transport with user defined change state and not to use ion effective charge;

standardNR The physics constructor, in which multiple scattering processes for protons and ions are substituted by single scattering process.

TestEm8 extended/electromagnetic example demonstrating how to activate PAI model per region on top of any EM physics list using only UI command /process/em/AddPAIRegion all myregion.