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27 //
28 // Geant4 Class file
29 //
30 // File name: G4PolarizedGammaConversionXS
31 //
32 // Author: Andreas Schaelicke on the base of Karim Laihems code
33
34 #include "G4PolarizedGammaConversionXS.hh"
35
36 G4double G4PolarizedGammaConversionXS::SCRN[2][19] = {
37 { 0.5, 1.0, 2.0, 4.0, 8.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0,
38 60.0, 70.0, 80.0, 90.0, 100.0, 120.0 },
39 { 0.0145, 0.0490, 0.1400, 0.3312, 0.6758, 1.126, 1.367, 1.564, 1.731, 1.875,
40 2.001, 2.114, 2.216, 2.393, 2.545, 2.676, 2.793, 2.897, 3.078 }
41 };
42
43 G4PolarizedGammaConversionXS::G4PolarizedGammaConversionXS()
44 {
45 fFinalElectronPolarization = G4StokesVector::ZERO;
46 fFinalPositronPolarization = G4StokesVector::ZERO;
47 }
48
49 G4PolarizedGammaConversionXS::~G4PolarizedGammaConversionXS() {}
50
51 void G4PolarizedGammaConversionXS::Initialize(
52 G4double aGammaE, G4double aLept0E, G4double sintheta,
53 const G4StokesVector& beamPol, const G4StokesVector& /*p1*/, G4int /*flag*/)
54 {
55 G4double aLept1E = aGammaE - aLept0E;
56
57 G4double Stokes_P3 = beamPol.z();
58
59 G4double Lept0E = aLept0E / CLHEP::electron_mass_c2 + 1.;
60 G4double Lept0E2 = Lept0E * Lept0E;
61 G4double GammaE = aGammaE / CLHEP::electron_mass_c2;
62 G4double Lept1E = aLept1E / CLHEP::electron_mass_c2 - 1.;
63 G4double Lept1E2 = Lept1E * Lept1E;
64
65 // ******* Gamma Transvers Momentum
66 G4double TMom = std::sqrt(Lept0E2 - 1.) * sintheta;
67 G4double u = TMom;
68 G4double u2 = u * u;
69 G4double Xsi = 1. / (1. + u2);
70 G4double Xsi2 = Xsi * Xsi;
71
72 G4double delta =
73 12. * std::pow(fZ, 1. / 3.) * Lept0E * Lept1E * Xsi / (121. * GammaE);
74 G4double GG = 0.;
75
76 if(delta < 0.5)
77 {
78 GG = std::log(2. * Lept0E * Lept1E / GammaE) - 2. - fCoul;
79 }
80 else if(delta < 120.)
81 {
82 for(G4int j = 1; j < 19; ++j)
83 {
84 if(SCRN[0][j] >= delta)
85 {
86 GG = std::log(2. * Lept0E * Lept1E / GammaE) - 2. - fCoul -
87 (SCRN[1][j - 1] + (delta - SCRN[0][j - 1]) *
88 (SCRN[1][j] - SCRN[1][j - 1]) /
89 (SCRN[0][j] - SCRN[0][j - 1]));
90 break;
91 }
92 }
93 }
94 else
95 {
96 G4double alpha_sc = (111. * std::pow(fZ, -1. / 3.)) / Xsi;
97 GG = std::log(alpha_sc) - 2. - fCoul;
98 }
99
100 if(GG < -1.)
101 GG = -1.;
102
103 G4double I_Lepton = (Lept0E2 + Lept1E2) * (3 + 2 * GG) +
104 2. * Lept0E * Lept1E * (1. + 4. * u2 * Xsi2 * GG);
105
106 G4double L_Lepton1 = GammaE *
107 ((Lept0E - Lept1E) * (3. + 2. * GG) +
108 2 * Lept1E * (1. + 4. * u2 * Xsi2 * GG)) /
109 I_Lepton;
110
111 G4double T_Lepton1 =
112 4. * GammaE * Lept1E * Xsi * u * (1. - 2. * Xsi) * GG / I_Lepton;
113
114 G4double Stokes_S1 = (Stokes_P3 * T_Lepton1);
115 G4double Stokes_S2 = 0.;
116 G4double Stokes_S3 = (Stokes_P3 * L_Lepton1);
117
118 fFinalElectronPolarization.setX(Stokes_S1);
119 fFinalElectronPolarization.setY(Stokes_S2);
120 fFinalElectronPolarization.setZ(Stokes_S3);
121
122 if(fFinalElectronPolarization.mag2() > 1.)
123 {
124 G4ExceptionDescription ed;
125 ed << "\t" << fFinalElectronPolarization << "\t GG\t" << GG << "\t delta\t"
126 << delta << "\n";
127 G4Exception("G4PolarizedGammaConversionXS::Initialize", "pol022",
128 JustWarning, ed);
129 fFinalElectronPolarization.setX(0.);
130 fFinalElectronPolarization.setY(0.);
131 fFinalElectronPolarization.setZ(Stokes_S3);
132 if(Stokes_S3 > 1.)
133 fFinalElectronPolarization.setZ(1.);
134 }
135
136 G4double L_Lepton2 = GammaE *
137 ((Lept1E - Lept0E) * (3. + 2. * GG) +
138 2 * Lept0E * (1. + 4. * u2 * Xsi2 * GG)) /
139 I_Lepton;
140
141 G4double T_Lepton2 =
142 4. * GammaE * Lept0E * Xsi * u * (1. - 2. * Xsi) * GG / I_Lepton;
143
144 G4double Stokes_SS1 = (Stokes_P3 * T_Lepton2);
145 G4double Stokes_SS2 = 0.;
146 G4double Stokes_SS3 = (Stokes_P3 * L_Lepton2);
147
148 fFinalPositronPolarization.SetPhoton();
149
150 fFinalPositronPolarization.setX(Stokes_SS1);
151 fFinalPositronPolarization.setY(Stokes_SS2);
152 fFinalPositronPolarization.setZ(Stokes_SS3);
153
154 if(fFinalPositronPolarization.mag2() > 1.)
155 {
156 G4ExceptionDescription ed;
157 ed << "\t" << fFinalPositronPolarization << "\t GG\t" << GG << "\t delta\t"
158 << delta << "\n";
159 G4Exception("G4PolarizedGammaConversionXS::Initialize", "pol023",
160 JustWarning, ed);
161 }
162 }
163
164 G4double G4PolarizedGammaConversionXS::XSection(const G4StokesVector& /*pol2*/,
165 const G4StokesVector& /*pol3*/)
166 {
167 G4ExceptionDescription ed;
168 ed << "ERROR dummy routine G4PolarizedGammaConversionXS::XSection "
169 "called \n";
170 G4Exception("G4PolarizedGammaConversionXS::Initialize", "pol024",
171 FatalException, ed);
172 return 0.;
173 }
174
175 // return expected mean polarisation
176 G4StokesVector G4PolarizedGammaConversionXS::GetPol2()
177 {
178 // electron/positron
179 return fFinalElectronPolarization;
180 }
181
182 G4StokesVector G4PolarizedGammaConversionXS::GetPol3()
183 {
184 // photon
185 return fFinalPositronPolarization;
186 }
187