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// -------------------------------------------------------------------
//      GEANT 4 class implementation file 
//
//      CERN, Geneva, Switzerland
//
//      File name:     G4PionPlusField.cc
//
//      Author:        Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
// 
//      Creation date: 5 June 2000
// -------------------------------------------------------------------
#include "G4PionPlusField.hh"
#include "G4NucleiProperties.hh"
#include "G4VNuclearDensity.hh"
#include "G4FermiMomentum.hh"
#include "G4PionPlus.hh"
#include "G4HadTmpUtil.hh"


G4PionPlusField::G4PionPlusField(G4V3DNucleus * nucleus, G4double coeff)
  : G4VNuclearField(nucleus)
{
  theCoeff = coeff;
}


G4PionPlusField::~G4PionPlusField()
{ }


const G4PionPlusField & G4PionPlusField::operator=(const G4PionPlusField &)
{
  throw G4HadronicException(__FILE__, __LINE__, "G4PionPlusField::operator= meant not to be accessible");
  return *this;
}


G4int G4PionPlusField::operator==(const G4PionPlusField &) const
{
  throw G4HadronicException(__FILE__, __LINE__, "G4PionPlusField::operator== meant not to be accessible");
  return 0;
}


G4int G4PionPlusField::operator!=(const G4PionPlusField &) const
{
  throw G4HadronicException(__FILE__, __LINE__, "G4PionPlusField::operator!= meant not to be accessible");
  return 1;
}


G4double G4PionPlusField::GetField(const G4ThreeVector & aPosition)
{
// Field is 0 out of the nucleus!
  if(aPosition.mag() >= radius) return 0.0;

  G4double pionPlusMass = G4PionPlus::PionPlus()->GetPDGMass();

  G4double A = theNucleus->GetMassNumber();
  G4double Z = theNucleus->GetCharge();
  G4double bindingEnergy = G4NucleiProperties::GetBindingEnergy(G4lrint(A), G4lrint(Z));
  G4double nucleusMass = Z*proton_mass_c2+(A-Z)*neutron_mass_c2+bindingEnergy;
  G4double reducedMass = pionPlusMass*nucleusMass/(pionPlusMass+nucleusMass);

  G4double density = A*theNucleus->GetNuclearDensity()->GetDensity(aPosition);
  G4double nucleonMass = (proton_mass_c2+neutron_mass_c2)/2;

  return 2.*pi*hbarc*hbarc/reducedMass*(1+pionPlusMass/nucleonMass)*theCoeff*density + GetBarrier();
}


G4double G4PionPlusField::GetBarrier()
{
  G4double A = theNucleus->GetMassNumber();
  G4double Z = theNucleus->GetCharge();
  G4double coulombBarrier = (1.44/1.14) * MeV * Z / (1.0 + std::pow(A,1./3.));
  return coulombBarrier;
}