G4PionPlusField.cc

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00026 //
00027 // -------------------------------------------------------------------
00028 //      GEANT 4 class implementation file 
00029 //
00030 //      CERN, Geneva, Switzerland
00031 //
00032 //      File name:     G4PionPlusField.cc
00033 //
00034 //      Author:        Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
00035 // 
00036 //      Creation date: 5 June 2000
00037 // -------------------------------------------------------------------
00038 
00039 #include "G4PionPlusField.hh"
00040 #include "G4PhysicalConstants.hh"
00041 #include "G4SystemOfUnits.hh"
00042 #include "G4NucleiProperties.hh"
00043 #include "G4VNuclearDensity.hh"
00044 #include "G4FermiMomentum.hh"
00045 #include "G4PionPlus.hh"
00046 #include "G4HadTmpUtil.hh"
00047 
00048 G4PionPlusField::G4PionPlusField(G4V3DNucleus * nucleus, G4double coeff)
00049   : G4VNuclearField(nucleus)
00050 {
00051   theCoeff = coeff;
00052 }
00053 
00054 
00055 G4PionPlusField::~G4PionPlusField()
00056 { }
00057 
00058 G4double G4PionPlusField::GetField(const G4ThreeVector & aPosition)
00059 {
00060 // Field is 0 out of the nucleus!
00061   if(aPosition.mag() >= radius) return 0.0;
00062 
00063   G4double pionPlusMass = G4PionPlus::PionPlus()->GetPDGMass();
00064 
00065   G4int A = theNucleus->GetMassNumber();
00066   G4int Z = theNucleus->GetCharge();
00067   G4double bindingEnergy = G4NucleiProperties::GetBindingEnergy(A, Z);
00068   G4double nucleusMass = Z*proton_mass_c2+(A-Z)*neutron_mass_c2+bindingEnergy;
00069   G4double reducedMass = pionPlusMass*nucleusMass/(pionPlusMass+nucleusMass);
00070 
00071   G4double density = A*theNucleus->GetNuclearDensity()->GetDensity(aPosition);
00072   G4double nucleonMass = (proton_mass_c2+neutron_mass_c2)/2;
00073 
00074   return 2.*pi*hbarc*hbarc/reducedMass*(1+pionPlusMass/nucleonMass)*theCoeff*density + GetBarrier();
00075 }
00076 
00077 
00078 G4double G4PionPlusField::GetBarrier()
00079 {
00080   G4int A = theNucleus->GetMassNumber();
00081   G4int Z = theNucleus->GetCharge();
00082   G4double coulombBarrier = (1.44/1.14) * MeV * Z / (1.0 + std::pow(A,1./3.));
00083   return coulombBarrier;
00084 }

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