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27 // -------------------------------------------------------------------
28 // GEANT 4 class implementation file
29 //
30 // CERN, Geneva, Switzerland
31 //
32 // File name: G4SigmaMinusField.cc
33 //
34 // Author: Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
35 //
36 // Creation date: 5 June 2000
37 // -------------------------------------------------------------------
38
39 #include "G4SigmaMinusField.hh"
40 #include "G4PhysicalConstants.hh"
41 #include "G4SystemOfUnits.hh"
42 #include "G4NucleiProperties.hh"
43 #include "G4VNuclearDensity.hh"
44 #include "G4FermiMomentum.hh"
45 #include "G4SigmaMinus.hh"
46 #include "G4HadTmpUtil.hh"
47 #include "G4Pow.hh"
48
49 G4SigmaMinusField::G4SigmaMinusField(G4V3DNucleus * nucleus, G4double coeff)
50 : G4VNuclearField(nucleus)
51 {
52 theCoeff = coeff;
53 }
54
55 G4SigmaMinusField::~G4SigmaMinusField()
56 { }
57
58 G4double G4SigmaMinusField::GetField(const G4ThreeVector & aPosition)
59 {
60 // Field is 0 out of the nucleus!
61 if(aPosition.mag() >= radius) return 0.0;
62
63 G4double sigmaMinusMass = G4SigmaMinus::SigmaMinus()->GetPDGMass();
64
65 G4int A = theNucleus->GetMassNumber();
66 G4int Z = theNucleus->GetCharge();
67 G4double bindingEnergy = G4NucleiProperties::GetBindingEnergy(A, Z);
68 G4double nucleusMass = Z*proton_mass_c2+(A-Z)*neutron_mass_c2+bindingEnergy;
69 G4double reducedMass = sigmaMinusMass*nucleusMass/(sigmaMinusMass+nucleusMass);
70
71 const G4VNuclearDensity * nuclearDensity=theNucleus->GetNuclearDensity();
72 G4double density = nuclearDensity->GetDensity(aPosition);
73
74 return -2.*pi*hbarc*hbarc/reducedMass*(2.0)*theCoeff*density+GetBarrier();
75 }
76
77 G4double G4SigmaMinusField::GetBarrier()
78 {
79 G4double A = theNucleus->GetMassNumber();
80 G4double Z = theNucleus->GetCharge();
81 G4double coulombBarrier = (1.44/1.14) * MeV * Z / (1.0 + G4Pow::GetInstance()->A13(A));
82 return -coulombBarrier;
83 }
84
85