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// $Id: G4FissionProbability.cc,v 1.10 2010/11/17 20:22:46 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-04-ref-00 $
//
// Hadronic Process: Nuclear De-excitations
// by V. Lara (Oct 1998)
//
//
// J.M.Quesada (14 february 2009) bug fixed in fission width: missing parenthesis in the denominator 


#include "G4FissionProbability.hh"
#include "G4PairingCorrection.hh"

G4FissionProbability::G4FissionProbability()
{}

G4FissionProbability::~G4FissionProbability()
{}


G4double 
G4FissionProbability::EmissionProbability(const G4Fragment & fragment, 
					  G4double MaximalKineticEnergy)
  // Compute integrated probability of fission channel
{
  if (MaximalKineticEnergy <= 0.0) return 0.0;
  G4int A = fragment.GetA_asInt();
  G4int Z = fragment.GetZ_asInt();
  G4double U = fragment.GetExcitationEnergy();
  
  G4double Ucompound = U - 
    G4PairingCorrection::GetInstance()->GetPairingCorrection(A,Z);

  G4double Ufission = U - 
    G4PairingCorrection::GetInstance()->GetFissionPairingCorrection(A,Z);
  
  G4double SystemEntropy = 
    2.0*std::sqrt(theEvapLDP.LevelDensityParameter(A,Z,Ucompound)*Ucompound);
	
  G4double afission = theFissLDP.LevelDensityParameter(A,Z,Ufission);

  G4double Cf = 2.0*std::sqrt(afission*MaximalKineticEnergy);

  //    G4double Q1 = 1.0 + (Cf - 1.0)*std::exp(Cf);
  //    G4double Q2 = 4.0*pi*afission*std::exp(SystemEntropy);
  
  //    G4double probability = Q1/Q2;
   
  G4double Exp1 = 0.0;
  if (SystemEntropy <= 160.0) { Exp1 = std::exp(-SystemEntropy); }
  // @@@@@@@@@@@@@@@@@ hpw changed max to min - cannot notify vicente now
  G4double Exp2 = std::exp( std::min(700.0,Cf-SystemEntropy) ); 

  // JMQ 14/02/09 BUG fixed in fission probability (missing parenthesis 
  // at denominator)
  //AH fix from Vincente: G4double probability = 
  //        (Exp1 + (1.0-Cf)*Exp2) / 4.0*pi*afission;
  //    G4double probability = (Exp1 + (Cf-1.0)*Exp2) / 4.0*pi*afission;
  G4double probability = (Exp1 + (Cf-1.0)*Exp2) / (4.0*pi*afission);

  return probability;
}