G4PionPlusField.cc

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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 "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.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()
{ }

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();

  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 = 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()
{
  G4int A = theNucleus->GetMassNumber();
  G4int Z = theNucleus->GetCharge();
  G4double coulombBarrier = (1.44/1.14) * MeV * Z / (1.0 + std::pow(A,1./3.));
  return coulombBarrier;
}