Geant4 User's Guide for Application Developers - Geant4 - CERN

Tracking and PhysicsG4double theDynamicalMassG4ThreeVector theMomentumDirectionG4ParticleDefinition* theParticleDefinitionG4double theDynamicalSpinG4ThreeVector thePolarizationG4double theMagneticMomentG4double theKineticEnergyG4double theProperTimeG4double theDynamicalChargeG4ElectronOccupancy* theElectronOccupancyTable 5.4. Methods to set/get cut off values.dynamical massnormalized momentum vectordefinition of particledynamical spin (i.e. total angular momentum as a ion/atom )polarization vectordynamical magnetic moment (i.e. total magnetic momentas a ion/atom )kinetic energyproper timedynamical electric charge (i.e. total electric charge as aion/atom )electron orbits for ionsHere, the dynamical mass is defined as the mass for the dynamic particle. For most cases, it is same as the massdefined in G4ParticleDefinition class ( i.e. mass value given by GetPDGMass() method). However, there aretwo exceptions.• resonance particle• ionsResonance particles have large mass width and the total energy of decay products at the center of mass systemcan be different event by event.As for ions, G4ParticleDefintion defines a nucleus and G4DynamicParticle defines an atom.G4ElectronOccupancy describes state of orbital electrons. So, the dynamic mass can be different from the PDGmass by the mass of electrons (and their binding energy). In addition, the dynamical charge, spin and magneticmoment are those of the atom/ion (i.e. including nucleus and orbit electrons).Decay products of heavy flavor particles are given in many event generators. In such cases, G4VPrimaryGeneratorsets this information in *thePreAssignedDecayProducts. In addition, decay time of the particle can beset arbitrarily time by using PreAssignedDecayProperTime.5.4. Production Threshold versus Tracking Cut5.4.1. General considerationsWe have to fulfill two contradictory requirements. It is the responsibility of each individual process to producesecondary particles according to its own capabilities. On the other hand, it is only the Geant4 kernel (i.e., tracking)which can ensure an overall coherence of the simulation.The general principles in Geant4 are the following:1. Each process has its intrinsic limit(s) to produce secondary particles.2. All particles produced (and accepted) will be tracked up to zero range.3. Each particle has a suggested cut in range (which is converted to energy for all materials), and defined via aSetCut() method (see Section 2.4.2).Points 1 and 2 imply that the cut associated with the particle is a (recommended) production threshold of secondaryparticles.183