G4PionZeroField.cc

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// -------------------------------------------------------------------
//      GEANT 4 class implementation file 
//
//      CERN, Geneva, Switzerland
//
//      File name:     G4PionZeroField.cc
//
//      Author:        Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
// 
//      Creation date: 5 June 2000
// -------------------------------------------------------------------

#include "G4PionZeroField.hh"
#include "G4PhysicalConstants.hh"
#include "G4NucleiProperties.hh"
#include "G4VNuclearDensity.hh"
#include "G4FermiMomentum.hh"
#include "G4PionZero.hh"
#include "G4HadTmpUtil.hh"

G4PionZeroField::G4PionZeroField(G4V3DNucleus * nucleus, G4double coeff)
  : G4VNuclearField(nucleus)
{
  theCoeff = coeff;
}


G4PionZeroField::~G4PionZeroField()
{ }

G4double G4PionZeroField::GetField(const G4ThreeVector & aPosition)
{
// Field is 0 out of the nucleus!
  if(aPosition.mag() >= radius) return 0.0;

  G4double pionZeroMass = G4PionZero::PionZero()->GetPDGMass();
  G4int A = theNucleus->GetMassNumber();
  G4int Z = theNucleus->GetCharge();

  G4double bindingEnergy = G4NucleiProperties::GetBindingEnergy(A, Z);
  G4double nucleusMass = Z*proton_mass_c2+(A-Z)*neutron_mass_c2+bindingEnergy;
  G4double reducedMass = pionZeroMass*nucleusMass/(pionZeroMass+nucleusMass);


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

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

G4double G4PionZeroField::GetBarrier()
{
  return 0;
}