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// $Id: G4PairingCorrection.cc,v 1.8 2010/11/15 12:41:58 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-04-ref-00 $
//
// Hadronic Process: Nuclear De-excitations
// by V. Lara


#include "G4PairingCorrection.hh"

G4PairingCorrection* G4PairingCorrection::theInstance = 0;

G4PairingCorrection::G4PairingCorrection()
{
  theCookPairingCorrections =  G4CookPairingCorrections::GetInstance();
  theCameronGilbertPairingCorrections = G4CameronGilbertPairingCorrections::GetInstance();
//  theCameronTruranHilfPairingCorrections = G4CameronTruranHilfPairingCorrections::GetInstance();
}

G4PairingCorrection::~G4PairingCorrection()
{;}

G4PairingCorrection* G4PairingCorrection::GetInstance()
{
  if (!theInstance)  { 
    static G4PairingCorrection theCorrections;
    theInstance = &theCorrections; 
  }
  return theInstance;
}   

G4double G4PairingCorrection::GetPairingCorrection(G4int A, G4int Z) const
{
  G4double PCorrection = 0.0;
  G4int N = A - Z;
  if (theCookPairingCorrections->IsInTableThisN(N) &&
      theCookPairingCorrections->IsInTableThisZ(Z)) 
    PCorrection = theCookPairingCorrections->GetParingCorrection(A,Z);
  else if (theCameronGilbertPairingCorrections->IsInTableThisN(N) &&
	   theCameronGilbertPairingCorrections->IsInTableThisZ(Z))
    PCorrection = theCameronGilbertPairingCorrections->GetPairingCorrection(A,Z);
  else {
    const G4double PairingConstant = 12.0*MeV;
    G4double Pair = (1 - Z + 2*(Z/2)) + (1 - N + 2*(N/2));
    PCorrection = Pair*PairingConstant/std::sqrt(static_cast<G4double>(A));
  }
  return std::max(PCorrection,0.0);
}


G4double G4PairingCorrection::GetFissionPairingCorrection(G4int A, G4int Z) const 
{
  const G4double PairingConstant = 14.0*MeV;
  G4int N = A - Z;
  G4double Pair = (1 - Z + 2*(Z/2)) + (1 - N + 2*(N/2));
  G4double PCorrection = Pair*PairingConstant/std::sqrt(static_cast<G4double>(A));
  return PCorrection;
}
