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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4ModifiedTsai
33 //
34 // Author: Andreia Trindade (andreia@lip.pt)
35 // Pedro Rodrigues (psilva@lip.pt)
36 // Luis Peralta (luis@lip.pt)
37 //
38 // Creation date: 21 March 2003
39 //
40 // Modifications:
41 // 21 Mar 2003 A.Trindade First implementation acording with new design
42 // 24 Mar 2003 A.Trindade Fix in Tsai generator in order to prevent theta
43 // generation above pi
44 // 13 Oct 2010 V.Ivanchenko Moved to standard and improved comment
45 // 26.04.2011 V.Grichine Clean-up of PolarAngle method
46 //
47 // Class Description:
48 //
49 // Bremsstrahlung Angular Distribution Generation
50 // suggested by L.Urban (Geant3 manual (1993) Phys211)
51 // Derived from Tsai distribution (Rev Mod Phys 49,421(1977))
52 //
53 // Class Description: End
54 //
55 // -------------------------------------------------------------------
56 //
57
58 #include "G4ModifiedTsai.hh"
59 #include "Randomize.hh"
60 #include "G4Log.hh"
61 #include <CLHEP/Units/PhysicalConstants.h>
62
63 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
64
65 G4ModifiedTsai::G4ModifiedTsai(const G4String&)
66 : G4VEmAngularDistribution("ModifiedTsai")
67 {}
68
69 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
70
71 G4ModifiedTsai::~G4ModifiedTsai() = default;
72
73 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
74
75 G4ThreeVector&
76 G4ModifiedTsai::SampleDirection(const G4DynamicParticle* dp,
77 G4double, G4int, const G4Material*)
78 {
79 // Sample gamma angle (Z - axis along the parent particle).
80 G4double cost = SampleCosTheta(dp->GetKineticEnergy());
81 G4double sint = std::sqrt((1 - cost)*(1 + cost));
82 G4double phi = CLHEP::twopi*G4UniformRand();
83
84 fLocalDirection.set(sint*std::cos(phi), sint*std::sin(phi), cost);
85 fLocalDirection.rotateUz(dp->GetMomentumDirection());
86
87 return fLocalDirection;
88 }
89
90 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
91
92 G4double G4ModifiedTsai::SampleCosTheta(G4double kinEnergy)
93 {
94 // Universal distribution suggested by L. Urban (Geant3 manual (1993)
95 // Phys211) derived from Tsai distribution (Rev Mod Phys 49,421(1977))
96
97 G4double uMax = 2*(1. + kinEnergy/CLHEP::electron_mass_c2);
98
99 static const G4double a1 = 1.6;
100 static const G4double a2 = a1/3.;
101 static const G4double border = 0.25;
102 G4double u;
103 CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
104
105 do {
106 G4double uu = -G4Log(rndmEngine->flat()*rndmEngine->flat());
107 u = (border > rndmEngine->flat()) ? uu*a1 : uu*a2;
108
109 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
110 } while(u > uMax);
111
112 return 1.0 - 2.0*u*u/(uMax*uMax);
113 }
114
115 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
116
117 void G4ModifiedTsai::SamplePairDirections(const G4DynamicParticle* dp,
118 G4double elecKinEnergy,
119 G4double posiKinEnergy,
120 G4ThreeVector& dirElectron,
121 G4ThreeVector& dirPositron,
122 G4int, const G4Material*)
123 {
124 G4double phi = CLHEP::twopi * G4UniformRand();
125 G4double sinp = std::sin(phi);
126 G4double cosp = std::cos(phi);
127
128 G4double cost = SampleCosTheta(elecKinEnergy);
129 G4double sint = std::sqrt((1. - cost)*(1. + cost));
130
131 dirElectron.set(sint*cosp, sint*sinp, cost);
132 dirElectron.rotateUz(dp->GetMomentumDirection());
133
134 cost = SampleCosTheta(posiKinEnergy);
135 sint = std::sqrt((1. - cost)*(1. + cost));
136
137 dirPositron.set(-sint*cosp, -sint*sinp, cost);
138 dirPositron.rotateUz(dp->GetMomentumDirection());
139 }
140
141 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
142
143 void G4ModifiedTsai::PrintGeneratorInformation() const
144 {
145 G4cout << "\n" << G4endl;
146 G4cout << "Bremsstrahlung Angular Generator is Modified Tsai" << G4endl;
147 G4cout << "Distribution suggested by L.Urban (Geant3 manual (1993) Phys211)"
148 << G4endl;
149 G4cout << "Derived from Tsai distribution (Rev Mod Phys 49,421(1977)) \n"
150 << G4endl;
151 }
152
153 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
154