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26 // -------------------------------------------------------------------
27 //
28 // Geant4 Class file
29 //
30 // File name: G4PolarizedGammaConversionModel
31 //
32 // Author: Karim Laihem
33 //
34 // Class Description:
35 // Implementation of gamma conversion to e+e- in the field of a nucleus
36 // including polarization transfer
37
38 #include "G4PolarizedGammaConversionModel.hh"
39
40 #include "G4DataVector.hh"
41 #include "G4DynamicParticle.hh"
42 #include "G4MaterialCutsCouple.hh"
43 #include "G4PolarizedGammaConversionXS.hh"
44 #include "G4PolarizationHelper.hh"
45 #include "G4StokesVector.hh"
46
47 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
48 G4PolarizedGammaConversionModel::G4PolarizedGammaConversionModel(
49 const G4ParticleDefinition* pd, const G4String& nam)
50 : G4BetheHeitlerModel(pd, nam)
51 , fCrossSectionCalculator(nullptr)
52 {}
53
54 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55 G4PolarizedGammaConversionModel::~G4PolarizedGammaConversionModel()
56 {
57 if(fCrossSectionCalculator)
58 delete fCrossSectionCalculator;
59 }
60
61 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
62 void G4PolarizedGammaConversionModel::Initialise(const G4ParticleDefinition* pd,
63 const G4DataVector& dv)
64 {
65 G4BetheHeitlerModel::Initialise(pd, dv);
66 if(!fCrossSectionCalculator)
67 fCrossSectionCalculator = new G4PolarizedGammaConversionXS();
68 }
69
70 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
71 void G4PolarizedGammaConversionModel::SampleSecondaries(
72 std::vector<G4DynamicParticle*>* vdp, const G4MaterialCutsCouple* couple,
73 const G4DynamicParticle* dp, G4double tmin, G4double maxEnergy)
74 {
75 G4BetheHeitlerModel::SampleSecondaries(vdp, couple, dp, tmin, maxEnergy);
76
77 if(vdp && vdp->size() > 0)
78 {
79 G4double gamEnergy0 = dp->GetKineticEnergy();
80 G4double lepEnergy1 = (*vdp)[0]->GetKineticEnergy();
81 G4double sintheta =
82 dp->GetMomentumDirection().cross((*vdp)[0]->GetMomentumDirection()).mag();
83 if(sintheta > 1.)
84 sintheta = 1.;
85
86 G4StokesVector beamPol = G4StokesVector(dp->GetPolarization());
87 beamPol.SetPhoton();
88
89 // determine interaction plane
90 G4ThreeVector nInteractionFrame = G4PolarizationHelper::GetFrame(
91 dp->GetMomentumDirection(), (*vdp)[0]->GetMomentumDirection());
92
93 // transform polarization into interaction frame
94 beamPol.InvRotateAz(nInteractionFrame, dp->GetMomentumDirection());
95
96 // calculate polarization transfer
97 fCrossSectionCalculator->SetMaterial(
98 GetCurrentElement()->GetN(), // number of nucleons
99 GetCurrentElement()->GetZ(), GetCurrentElement()->GetfCoulomb());
100 fCrossSectionCalculator->Initialize(gamEnergy0, lepEnergy1, sintheta,
101 beamPol, G4StokesVector::ZERO);
102
103 // determine final state polarization
104 G4StokesVector lep1Pol = fCrossSectionCalculator->GetPol2();
105 lep1Pol.RotateAz(nInteractionFrame, (*vdp)[0]->GetMomentumDirection());
106 (*vdp)[0]->SetPolarization(lep1Pol.p1(), lep1Pol.p2(), lep1Pol.p3());
107
108 size_t num = vdp->size();
109 if(num != 2)
110 {
111 G4ExceptionDescription ed;
112 ed << " WARNING " << num
113 << " secondaries in polarized pairproduction not supported!\n";
114 G4Exception("G4PolarizedGammaConversionModel::SampleSecondaries",
115 "pol018", JustWarning, ed);
116 }
117 for(size_t i = 1; i < num; ++i)
118 {
119 G4StokesVector lep2Pol = fCrossSectionCalculator->GetPol3();
120 lep2Pol.RotateAz(nInteractionFrame, (*vdp)[i]->GetMomentumDirection());
121 (*vdp)[i]->SetPolarization(lep2Pol.p1(), lep2Pol.p2(), lep2Pol.p3());
122 }
123 }
124 }
125