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Geant4/processes/biasing/generic/include/G4BOptnLeadingParticle.hh

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  //
  // G4BOptnLeadingParticle
  //
  // Class Description:
  //
  // A G4VBiasingOperation that implements the so-called "Leading
  // particle biasing scheme". It is of interest in the shield problem
  // to estimate the flux leaking from the shield.
  // It works as follows:
  // - it is intented for hadronic inelastic interaction
  // - at each interaction, are kept:
  //     - the most energetic particle (the leading particle)
  //         - with unmodified weight
  //     - randomly one particle of each species
  //         - with this particle weight = n * primary_weight where
  //           n is the number of particles of this species
  //
  // Author: Marc Verderi, November 2019.
  // --------------------------------------------------------------------
  
  #ifndef G4BOptnLeadingParticle_hh
  #define G4BOptnLeadingParticle_hh 1
  
  #include "G4VBiasingOperation.hh"
  #include "G4ParticleChange.hh"
  
  class G4BOptnLeadingParticle : public G4VBiasingOperation
  {
    public:
  
      // -- Constructor :
      G4BOptnLeadingParticle(const G4String& name);
      // -- destructor:
      virtual ~G4BOptnLeadingParticle();
    
      // -- Methods from G4VBiasingOperation interface:
      // ----------------------------------------------
      // -- Unused:
      virtual const G4VBiasingInteractionLaw*
      ProvideOccurenceBiasingInteractionLaw( const G4BiasingProcessInterface*,
                                             G4ForceCondition& ) { return nullptr; }
      // -- Used:
      virtual G4VParticleChange*
      ApplyFinalStateBiasing( const G4BiasingProcessInterface*, // -- Method used for this biasing. The related biasing operator
                              const G4Track*,                   // -- returns this biasing operation at the post step do it level
                              const G4Step*,                    // -- when the wrapped process has won the interaction length race.
                              G4bool& );                        // -- The wrapped process final state is then trimmed.
      // -- Unused:
      virtual G4double
      DistanceToApplyOperation( const G4Track*, G4double, G4ForceCondition* ) { return 0.0; }
      virtual G4VParticleChange*
      GenerateBiasingFinalState( const G4Track*, const G4Step* ) { return nullptr; }
  
      // -- The possibility is given to further apply a Russian roulette on tracks that are accompagnying the leading particle
      // -- after the classical leading particle biasing algorithm has been applied.
      // -- This is of interest when applying the technique to e+ -> gamma gamma for example. Given one gamma is leading,
      // -- the second one is alone in its category, hence selected. With the Russian roulette it is then possible to keep
      // -- this one randomly. This is also of interest for pi0 decays, or for brem. e- -> e- gamma where the e- or gamma
      // -- are alone in their category.
      void SetFurtherKillingProbability( G4double p ) // -- if p <= 0.0 the killing is ignored.
      {
        fRussianRouletteKillingProbability = p;
      }
      G4double GetFurtherKillingProbability() const
      {
        return fRussianRouletteKillingProbability;
      }
  
    private:
  
      // -- Particle change used to return the trimmed final state:
      G4ParticleChange fParticleChange;
      G4double fRussianRouletteKillingProbability = -1.0;
  };
  
 #endif