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G4PolarizedGammaConversionModel.cc
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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4PolarizedGammaConversionModel
33 //
34 // Author: Karim Laihem
35 //
36 // Creation date: 19.04.2005
37 //
38 // Modifications:
39 // 21-08-06 Modified to fit in g4.8.1 framework (A.Schaelicke)
40 // 19-03-07 Add initialisation of crossSectionCalculator (VI)
41 //
42 // Class Description:
43 //
44 // Implementation of gamma convertion to e+e- in the field of a nucleus
45 // including polarization transfer
46 
47 // -------------------------------------------------------------------
48 //
49 
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52 
53 #include "G4PolarizedGammaConversionModel.hh"
54 #include "G4Electron.hh"
55 #include "G4Positron.hh"
56 #include "G4Gamma.hh"
57 #include "Randomize.hh"
58 #include "G4DataVector.hh"
59 #include "G4PhysicsLogVector.hh"
60 #include "G4ParticleChangeForGamma.hh"
61 #include "G4PolarizedPairProductionCrossSection.hh"
62 #include "G4PolarizationHelper.hh"
63 
64 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
65 
66 
67 G4PolarizedGammaConversionModel::G4PolarizedGammaConversionModel(const G4ParticleDefinition* pd,
68  const G4String& nam)
69  : G4BetheHeitlerModel(pd,nam), crossSectionCalculator(nullptr)
70 {
71 }
72 
73 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
74 
75 G4PolarizedGammaConversionModel::~G4PolarizedGammaConversionModel()
76 {
77  if (crossSectionCalculator) delete crossSectionCalculator;
78 }
79 
80 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
81 
82 void G4PolarizedGammaConversionModel::Initialise(const G4ParticleDefinition* pd,
83  const G4DataVector& dv)
84 {
85  G4BetheHeitlerModel::Initialise(pd,dv);
86  if (!crossSectionCalculator)
87  crossSectionCalculator = new G4PolarizedPairProductionCrossSection();
88 }
89 
90 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
91 
92 void G4PolarizedGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
93  const G4MaterialCutsCouple* couple,
94  const G4DynamicParticle* dp,
95  G4double tmin,
96  G4double maxEnergy)
97 {
98  G4BetheHeitlerModel::SampleSecondaries(vdp, couple, dp, tmin, maxEnergy);
99 
100  if(vdp && vdp->size()>0) {
101  G4double gamEnergy0 = dp->GetKineticEnergy();
102  G4double lepEnergy1 = (*vdp)[0]->GetKineticEnergy();
103  G4double sintheta = dp->GetMomentumDirection().cross((*vdp)[0]->GetMomentumDirection()).mag();
104  if (sintheta>1.) sintheta=1.;
105 
106  G4StokesVector beamPol = dp->GetPolarization();
107  beamPol.SetPhoton();
108 
109  // determine interaction plane
110  G4ThreeVector nInteractionFrame =
111  G4PolarizationHelper::GetFrame(dp->GetMomentumDirection(),
112  (*vdp)[0]->GetMomentumDirection());
113 
114  // transform polarization into interaction frame
115  beamPol.InvRotateAz(nInteractionFrame,dp->GetMomentumDirection());
116 
117  // calulcate polarization transfer
118  crossSectionCalculator->SetMaterial(GetCurrentElement()->GetN(), // number of nucleons
119  GetCurrentElement()->GetZ(),
120  GetCurrentElement()->GetfCoulomb());
121  crossSectionCalculator->Initialize(gamEnergy0, lepEnergy1, sintheta,
122  beamPol, G4StokesVector::ZERO);
123 
124  // deterimine final state polarization
125  G4StokesVector lep1Pol = crossSectionCalculator->GetPol2();
126  lep1Pol.RotateAz(nInteractionFrame,(*vdp)[0]->GetMomentumDirection());
127  (*vdp)[0]->SetPolarization(lep1Pol.p1(),
128  lep1Pol.p2(),
129  lep1Pol.p3());
130 
131  size_t num = vdp->size();
132  if (num!=2) G4cout<<" WARNING "<<num<<" secondaries in polarized pairproduction not supported!\n";
133  for (size_t i =1; i<num; ++i) {
134  G4StokesVector lep2Pol = crossSectionCalculator->GetPol3();
135  lep2Pol.RotateAz(nInteractionFrame,(*vdp)[i]->GetMomentumDirection());
136  (*vdp)[i]->SetPolarization(lep2Pol.p1(),
137  lep2Pol.p2(),
138  lep2Pol.p3());
139 
140  }
141  }
142 }
143 
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