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27 // -------------------------------------------------------------------
28 // GEANT 4 class implementation file
29 //
30 // CERN, Geneva, Switzerland
31 //
32 // File name: G4PionPlusField.cc
33 //
34 // Author: Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
35 //
36 // Creation date: 5 June 2000
37 // -------------------------------------------------------------------
38
39 #include "G4PionPlusField.hh"
40 #include "G4PhysicalConstants.hh"
41 #include "G4SystemOfUnits.hh"
42 #include "G4NucleiProperties.hh"
43 #include "G4VNuclearDensity.hh"
44 #include "G4FermiMomentum.hh"
45 #include "G4PionPlus.hh"
46 #include "G4HadTmpUtil.hh"
47 #include "G4Pow.hh"
48
49 G4PionPlusField::G4PionPlusField(G4V3DNucleus * nucleus, G4double coeff)
50 : G4VNuclearField(nucleus)
51 {
52 theCoeff = coeff;
53 }
54
55
56 G4PionPlusField::~G4PionPlusField()
57 { }
58
59 G4double G4PionPlusField::GetField(const G4ThreeVector & aPosition)
60 {
61 // Field is 0 out of the nucleus!
62 if(aPosition.mag() >= radius) return 0.0;
63
64 G4double pionPlusMass = G4PionPlus::PionPlus()->GetPDGMass();
65
66 G4int A = theNucleus->GetMassNumber();
67 G4int Z = theNucleus->GetCharge();
68 G4double bindingEnergy = G4NucleiProperties::GetBindingEnergy(A, Z);
69 G4double nucleusMass = Z*proton_mass_c2+(A-Z)*neutron_mass_c2+bindingEnergy;
70 G4double reducedMass = pionPlusMass*nucleusMass/(pionPlusMass+nucleusMass);
71
72 G4double density = A*theNucleus->GetNuclearDensity()->GetDensity(aPosition);
73 G4double nucleonMass = (proton_mass_c2+neutron_mass_c2)/2;
74
75 return 2.*pi*hbarc*hbarc/reducedMass*(1+pionPlusMass/nucleonMass)*theCoeff*density + GetBarrier();
76 }
77
78
79 G4double G4PionPlusField::GetBarrier()
80 {
81 G4int A = theNucleus->GetMassNumber();
82 G4int Z = theNucleus->GetCharge();
83 G4double coulombBarrier = (1.44/1.14) * MeV * Z / (1.0 + G4Pow::GetInstance()->Z13(A));
84 return coulombBarrier;
85 }
86