G4FermiDecayProbability.cc

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//
// FermiBreakUp de-excitation model
// by V. Ivanchenko (July 2016)
//

#include "G4FermiDecayProbability.hh"
#include "G4FermiFragment.hh"
#include "G4PhysicalConstants.hh"

G4FermiDecayProbability::G4FermiDecayProbability()
{}

G4FermiDecayProbability::~G4FermiDecayProbability()
{}

G4double 
G4FermiDecayProbability::ComputeProbability(G4int, G4int A, G4int spin,
              G4double etot, 
              const G4FermiFragment* f1,
              const G4FermiFragment* f2) const
{
  G4double prob = 0.0;
  G4double mass1 = f1->GetTotalEnergy();
  G4double mass2 = f2->GetTotalEnergy();
  G4double bCouloumb = f1->GetCoulombBarrier(f2->GetA(), f2->GetZ(), 0.0);
  if(etot <= mass1 + mass2 + bCouloumb) { return prob; }
  
  //G4cout << "ComputeProbability M1= " << mass1 << " M2= " << mass2 << G4endl;
  G4double ekin = etot - mass1 - mass2;

  // mass factors
  G4double massFactor = mass1*mass2/(mass1 + mass2);
  massFactor *= std::sqrt(massFactor);

  // Spin factor S_n
  G4double S_n = 1.0;
  if(spin >= 0) {
    G4int spin1 = f1->GetSpin();
    G4int spin2 = f2->GetSpin();
    if(spin1 >= 0 && spin2 >= 0) {
      S_n = (spin1+1)*(spin2+1); 
    }
  }
    
  // Permutation Factor G_n
  // search for identical fragments
  G4double G_n = (f1 == f2) ? 0.5 : 1.0;

  prob = A*massFactor*S_n*G_n*std::sqrt(ekin);

  //G4cout << "prob= " << prob << " Coeff= " << Coeff << G4endl;
  return prob; 
}