include/Geant4/G4VBiasingInteractionLaw.hh

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0025 //
0026 // G4VBiasingInteractionLaw
0027 //
0028 // Class Description:
0029 //
0030 // An abstract class to model interaction laws, not necessarily.
0031 // exponential ones.
0032 // These laws, p(l), are caraterized by their:
0033 //    - non-interaction probability over l:
0034 //      P_NI(l) = 1 - integral(0,l) p(s) ds
0035 //    - effective cross-section at l:
0036 //      sigma_eff(l) = p(l)/P_NI(l) (several forms exist)
0037 // If several laws compete, the resulting net law has:
0038 //    - an non-interaction probability over a lenght l which
0039 //      is the product of the individual non-interaction probabilities.
0040 //    - an effective cross-section which is the
0041 //      sum on the individual effective cross-sections.
0042 //
0043 // Author: M.Verderi (LLR), November 2013
0044 // --------------------------------------------------------------------
0045 #ifndef G4VBiasingInteractionLaw_hh
0046 #define G4VBiasingInteractionLaw_hh 1
0047
0048 #include "globals.hh"
0049 #include <vector>
0050
0051 class G4BiasingProcessInterface;
0052
0053 class G4VBiasingInteractionLaw
0054 {
0055   public:
0056
0057     G4VBiasingInteractionLaw(const G4String& name)
0058       : fName(name), fSampledInteractionLength(DBL_MAX) {}
0059     virtual ~G4VBiasingInteractionLaw() = default;
0060
0061     const G4String& GetName() const { return fName; }
0062
0063     // -- Compute non-interaction probability and effective cross-section:
0064     // -- (probability of interaction over dl =  effective_cross-section* dl)
0065     virtual G4double ComputeNonInteractionProbabilityAt(G4double length) const = 0;
0066     virtual G4double ComputeEffectiveCrossSectionAt(G4double length) const = 0;
0067
0068     // -- Methods to deal with singularities : null cross sections or infinite ones.
0069     // -- In such cases, weight can not always be computed.
0070     // -- Tells if this interaction law has singularities:
0071     virtual G4bool IsSingular() const { return false; }
0072     // -- method interrogated only in case interaction law is IsSingular() == true:
0073     virtual G4bool IsEffectiveCrossSectionInfinite() const { return false; }
0074
0075     // -----------------------------------------
0076     // -- public interface to protected methods:
0077     // -----------------------------------------
0078     G4double Sample()
0079     {
0080       fSampledInteractionLength = SampleInteractionLength();
0081       return fSampledInteractionLength;
0082     }
0083     G4double UpdateForStep(G4double truePathLength)
0084     {
0085       fSampledInteractionLength = UpdateInteractionLengthForStep(truePathLength);
0086       return fSampledInteractionLength;
0087     }
0088     G4double GetSampledInteractionLength() const
0089     {
0090       return fSampledInteractionLength;
0091     }
0092
0093   protected:
0094
0095     // -- Sample the distribution for point like interaction (PostStep ones)
0096     virtual G4double SampleInteractionLength() = 0;
0097
0098     // -- Convenience method, used in many daughters classes :
0099     // -- update the distribution for a made step of truePathLength size:
0100     virtual G4double UpdateInteractionLengthForStep(G4double /* truePathLength */)
0101       { return DBL_MAX; }
0102
0103   private:
0104
0105     G4String fName;
0106     G4double fSampledInteractionLength;
0107 };
0108
0109 #endif