| Geant4 Cross Reference |
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25 //
26 // G4VBiasingInteractionLaw
27 //
28 // Class Description:
29 //
30 // An abstract class to model interaction laws, not necessarily.
31 // exponential ones.
32 // These laws, p(l), are caraterized by their:
33 // - non-interaction probability over l:
34 // P_NI(l) = 1 - integral(0,l) p(s) ds
35 // - effective cross-section at l:
36 // sigma_eff(l) = p(l)/P_NI(l) (several forms exist)
37 // If several laws compete, the resulting net law has:
38 // - an non-interaction probability over a lenght l which
39 // is the product of the individual non-interaction probabilities.
40 // - an effective cross-section which is the
41 // sum on the individual effective cross-sections.
42 //
43 // Author: M.Verderi (LLR), November 2013
44 // --------------------------------------------------------------------
45 #ifndef G4VBiasingInteractionLaw_hh
46 #define G4VBiasingInteractionLaw_hh 1
47
48 #include "globals.hh"
49 #include <vector>
50
51 class G4BiasingProcessInterface;
52
53 class G4VBiasingInteractionLaw
54 {
55 public:
56
57 G4VBiasingInteractionLaw(const G4String& name)
58 : fName(name), fSampledInteractionLength(DBL_MAX) {}
59 virtual ~G4VBiasingInteractionLaw() = default;
60
61 const G4String& GetName() const { return fName; }
62
63 // -- Compute non-interaction probability and effective cross-section:
64 // -- (probability of interaction over dl = effective_cross-section* dl)
65 virtual G4double ComputeNonInteractionProbabilityAt(G4double length) const = 0;
66 virtual G4double ComputeEffectiveCrossSectionAt(G4double length) const = 0;
67
68 // -- Methods to deal with singularities : null cross sections or infinite ones.
69 // -- In such cases, weight can not always be computed.
70 // -- Tells if this interaction law has singularities:
71 virtual G4bool IsSingular() const { return false; }
72 // -- method interrogated only in case interaction law is IsSingular() == true:
73 virtual G4bool IsEffectiveCrossSectionInfinite() const { return false; }
74
75 // -----------------------------------------
76 // -- public interface to protected methods:
77 // -----------------------------------------
78 G4double Sample()
79 {
80 fSampledInteractionLength = SampleInteractionLength();
81 return fSampledInteractionLength;
82 }
83 G4double UpdateForStep(G4double truePathLength)
84 {
85 fSampledInteractionLength = UpdateInteractionLengthForStep(truePathLength);
86 return fSampledInteractionLength;
87 }
88 G4double GetSampledInteractionLength() const
89 {
90 return fSampledInteractionLength;
91 }
92
93 protected:
94
95 // -- Sample the distribution for point like interaction (PostStep ones)
96 virtual G4double SampleInteractionLength() = 0;
97
98 // -- Convenience method, used in many daughters classes :
99 // -- update the distribution for a made step of truePathLength size:
100 virtual G4double UpdateInteractionLengthForStep(G4double /* truePathLength */)
101 { return DBL_MAX; }
102
103 private:
104
105 G4String fName;
106 G4double fSampledInteractionLength;
107 };
108
109 #endif
110