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// $Id: G4HETCNeutron.cc,v 1.3 2010/08/28 15:16:55 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-03-ref-09 $
//
// by V. Lara
//
// Modified:
// 23.08.2010 V.Ivanchenko general cleanup, move constructor and destructor 
//            the source, use G4Pow

#include "G4HETCNeutron.hh"
#include "G4Neutron.hh"

G4HETCNeutron::G4HETCNeutron() 
  : G4HETCFragment(G4Neutron::Neutron(), &theNeutronCoulombBarrier)
{}

G4HETCNeutron::~G4HETCNeutron() 
{}

G4double G4HETCNeutron::GetAlpha()
{
  return 0.76+2.2/g4pow->Z13(GetRestA());
}
  
G4double G4HETCNeutron::GetBeta() 
{
  return (2.12/g4pow->Z23(GetRestA())-0.05)*MeV/GetAlpha();
}

G4double G4HETCNeutron::GetSpinFactor()
{
  // (2s+1)
  return 2.0;
}
  
G4double G4HETCNeutron::K(const G4Fragment & aFragment)
{
  // Number of protons in emitted fragment
  G4int Pa = GetZ();
  // Number of neutrons in emitted fragment 
  G4int Na = GetA() - Pa;

  G4int TargetZ = GetRestZ();
  G4int TargetA = GetRestA();
  G4double r = G4double(TargetZ)/G4double(TargetA);
  
  G4int P = aFragment.GetNumberOfParticles();
  G4int H = aFragment.GetNumberOfHoles();
  
  G4double result = 0.0;
  if (P > 0)
    {
      result = (H + Na/(1.0-r))/P;
    }
  
  return std::max(0.0,result);
}

G4double G4HETCNeutron::GetKineticEnergy(const G4Fragment & aFragment)
{
  G4int H = aFragment.GetNumberOfHoles();
  G4int Pb = aFragment.GetNumberOfParticles();
  G4int Nb = Pb + H;
  G4double g0 = (6.0/pi2)*aFragment.GetA_asInt()*theParameters->GetLevelDensity();
  
  G4double Ab = std::max(0.0,G4double(Pb*Pb+H*H+Pb-3*H)/(4.0*g0));
  G4double Emax = GetMaximalKineticEnergy() - Ab;
  
  G4double cut = GetBeta() / (GetBeta()+Emax/G4double(Nb+1));
  G4double x(0.0);
  if (G4UniformRand() <= cut)
    {
      x = BetaRand(Nb,1);
    }
  else 
    {
      x = BetaRand(Nb,2);
    }

  return Emax * (1.0 - x);
}