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26 //
27 /// \file GB05BOptnSplitAndKillByCrossSection.cc
28 /// \brief Implementation of the GB05BOptnSplitAndKillByCrossSection class
29
30 #include "GB05BOptnSplitAndKillByCrossSection.hh"
31
32 #include "Randomize.hh"
33
34 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
35
36 GB05BOptnSplitAndKillByCrossSection::GB05BOptnSplitAndKillByCrossSection(G4String name)
37 : G4VBiasingOperation(name), fParticleChange(), fInteractionLength(-1.0)
38 {}
39
40 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
41
42 GB05BOptnSplitAndKillByCrossSection::~GB05BOptnSplitAndKillByCrossSection() {}
43
44 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
45
46 G4double GB05BOptnSplitAndKillByCrossSection::DistanceToApplyOperation(const G4Track*, G4double,
47 G4ForceCondition* condition)
48 {
49 *condition = NotForced;
50
51 // -- Sample the exponential law using the total interaction length of processes
52 // -- to couterbalance for:
53 G4double proposedStepLength = -std::log(G4UniformRand()) * fInteractionLength;
54
55 return proposedStepLength;
56 }
57
58 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
59
60 G4VParticleChange*
61 GB05BOptnSplitAndKillByCrossSection::GenerateBiasingFinalState(const G4Track* track, const G4Step*)
62 {
63 // -- This method is called if we have limited the step.
64 // -- We hence make the splitting or killing.
65
66 // Get track weight:
67 G4double initialWeight = track->GetWeight();
68
69 // The "particle change" is the object to be used to communicate to
70 // the tracking the update of the primary state and/or creation
71 // secondary tracks.
72 fParticleChange.Initialize(*track);
73
74 // -- Splitting and killing factors.
75 // -- They are taken the same, but the killing factor can be make bigger.
76 G4double splittingFactor = 2.0;
77 G4double killingFactor = 2.0;
78
79 if (track->GetMomentumDirection().z() > 0) {
80 // -- We split if the track is moving forward:
81
82 // Define the tracks weight:
83 G4double weightOfTrack = initialWeight / splittingFactor;
84
85 // Ask currect track weight to be changed to new value:
86 fParticleChange.ProposeParentWeight(weightOfTrack);
87 // Now make clones of this track (this is the actual splitting):
88 // we will then have the primary and clone of it, hence the
89 // splitting by a factor 2:
90 G4Track* clone = new G4Track(*track);
91 clone->SetWeight(weightOfTrack);
92 fParticleChange.AddSecondary(clone);
93 // -- Below's call added for safety & illustration : inform particle change to not
94 // -- modify the clone (ie : daughter) weight to male it that of the
95 // -- primary. Here call not mandatory and both tracks have same weights.
96 fParticleChange.SetSecondaryWeightByProcess(true);
97 }
98 else {
99 // -- We apply Russian roulette if the track is moving backward:
100
101 // Shoot a random number (in ]0,1[ segment):
102 G4double random = G4UniformRand();
103 G4double killingProbability = 1.0 - 1.0 / killingFactor;
104 if (random < killingProbability) {
105 // We ask for the the track to be killed:
106 fParticleChange.ProposeTrackStatus(fStopAndKill);
107 }
108 else {
109 // In this case, the track survives. We change its weight
110 // to conserve weight among killed and survival tracks:
111 fParticleChange.ProposeParentWeight(initialWeight * killingFactor);
112 }
113 }
114
115 return &fParticleChange;
116 }
117
118 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
119