G4HadPhaseSpaceGenbod.hh

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// $Id$
//
// Multibody "phase space" generator using GENBOD (CERNLIB W515) method.
//
// Author:      Michael Kelsey (SLAC) <kelsey@slac.stanford.edu>

#ifndef G4HadPhaseSpaceGenbod_HH
#define G4HadPhaseSpaceGenbod_HH 1

#include "G4VHadPhaseSpaceAlgorithm.hh"


class G4HadPhaseSpaceGenbod : public G4VHadPhaseSpaceAlgorithm {
public:
  G4HadPhaseSpaceGenbod(G4int verbose=0);
  virtual ~G4HadPhaseSpaceGenbod() {;}

protected:
  virtual void GenerateMultiBody(G4double initialMass,
                                 const std::vector<G4double>& masses,
                                 std::vector<G4LorentzVector>& finalState);

protected:
  void Initialize(G4double initialMass,
                  const std::vector<G4double>& masses);
                          
  void FillRandomBuffer();

  void ComputeWeightScale(const std::vector<G4double>& masses);

  void FillEnergySteps(G4double initialMass,
                       const std::vector<G4double>& masses);

  void GenerateMomenta(const std::vector<G4double>& masses,
                       std::vector<G4LorentzVector>& finalState);

  void AccumulateFinalState(size_t i,
                            const std::vector<G4double>& masses,
                            std::vector<G4LorentzVector>& finalState);

  G4bool AcceptEvent() const;   // Use accept-reject to generate distribution
  G4double ComputeWeight() const;

private:
  size_t nFinal;                // Number of final state particles
  G4double totalMass;           // Sum of final state masses
  G4double massExcess;          // Available kinetic energy
  G4double weightMax;           // Maximum possible weight
  G4int nTrials;                // Accept/reject cycles taken

  std::vector<G4double> msum;   // Cumulative sum of masses
  std::vector<G4double> msq;    // Final state squared masses
  std::vector<G4double> rndm;   // Random sequence for effective masses
  std::vector<G4double> meff;   // Random final-state effective masses
  std::vector<G4double> pd;     // Random momentum magnitudes
};

#endif  /* G4HadPhaseSpaceGenbod_HH */