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2 | // ******************************************************************** |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4PolarizedComptonCrossSection.cc,v 1.4 2007/11/01 17:32:34 schaelic Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-04-beta-01 $ |
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28 | // |
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29 | // GEANT4 Class file |
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30 | // |
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31 | // |
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32 | // File name: G4PolarizedComptonCrossSection |
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33 | // |
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34 | // Author: Andreas Schaelicke |
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35 | // |
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36 | // Creation date: 15.05.2005 |
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37 | // |
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38 | // Modifications: |
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39 | // |
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40 | // Class Description: |
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41 | // determine the polarization of the final state |
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42 | // in a Compton scattering process employing the differential |
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43 | // cross section by F.W.Lipps & H.A.Tolhoek |
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44 | // ( Physica 20 (1954) 395 ) |
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45 | // recalculated by P.Starovoitov |
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46 | // |
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47 | #include "G4PolarizedComptonCrossSection.hh" |
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48 | #include "Randomize.hh" |
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49 | |
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50 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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51 | G4PolarizedComptonCrossSection::G4PolarizedComptonCrossSection() |
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52 | { |
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53 | SetYmin(0.); |
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54 | |
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55 | // G4cout<<"G4PolarizedComptonCrossSection() init\n"; |
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56 | |
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57 | re2 = classic_electr_radius * classic_electr_radius * sqr(4*pi/hbarc); |
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58 | // G4double unit_conversion = hbarc_squared ; |
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59 | // G4cout<<" (keV)^2* m^2 ="<<unit_conversion<<"\n"; |
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60 | phi0 = 0.; polXS = 0.; unpXS = 0.; |
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61 | phi2 = G4ThreeVector(0., 0., 0.); |
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62 | phi3 = G4ThreeVector(0., 0., 0.); |
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63 | polxx = polyy = polzz = polxz = polzx = polyz = polzy = polxy = polyx = 0.; |
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64 | diffXSFactor = 1.; |
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65 | totalXSFactor = 1.; |
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66 | } |
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67 | |
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68 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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69 | G4PolarizedComptonCrossSection::~G4PolarizedComptonCrossSection() |
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70 | {} |
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71 | |
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72 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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73 | void G4PolarizedComptonCrossSection::Initialize(G4double eps, G4double X, G4double , // phi |
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74 | const G4StokesVector & pol0, |
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75 | const G4StokesVector & pol1, |
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76 | G4int flag) |
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77 | { |
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78 | G4double cosT = 1. - (1./eps - 1.)/X; |
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79 | if(cosT > 1.+1.e-8) cosT = 1.; |
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80 | if(cosT < -1.-1.e-8) cosT = -1.; |
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81 | G4double cosT2 = cosT*cosT; |
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82 | G4double cosT3 = cosT2*cosT; |
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83 | G4double sinT2 = 1. - cosT2; |
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84 | if(sinT2 > 1. + 1.e-8) sinT2 = 1.; |
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85 | if(sinT2 < 0.) sinT2 = 0.; |
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86 | G4double sinT = std::sqrt(sinT2); |
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87 | G4double cos2T = 2.*cosT2 - 1.; |
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88 | G4double sin2T = 2.*sinT*cosT; |
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89 | G4double eps2 = sqr(eps); |
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90 | DefineCoefficients(pol0,pol1); |
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91 | diffXSFactor = re2/(4.*X); |
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92 | |
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93 | // unpolarized Cross Section |
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94 | unpXS = (eps2 + 1. - eps*sinT2)/(2.*eps); |
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95 | // initial polarization dependence |
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96 | polXS = -sinT2*pol0.x() + (1. - eps)*sinT*polzx + ((eps2 - 1.)/eps)*cosT*polzz; |
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97 | polXS *= 0.5; |
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98 | |
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99 | phi0 = unpXS + polXS; |
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100 | |
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101 | if (flag == 2 ){ |
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102 | // polarization of outgoing photon |
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103 | G4double PHI21 = -sinT2 + 0.5*(cos2T + 3.)*pol0.x() - ((1. - eps)/eps)*sinT*polzx; |
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104 | PHI21 *= 0.5; |
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105 | G4double PHI22 = cosT*pol0.y() + ((1. - eps)/(2.*eps))*sinT*polzy; |
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106 | G4double PHI23 = ((eps2 + 1.)/eps)*cosT*pol0.z() - ((1. - eps)/eps)*(eps*cosT2 + 1.)*pol1.z(); |
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107 | PHI23 += 0.5*(1. - eps)*sin2T*pol1.x(); |
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108 | PHI23 += (eps - 1.)*(-sinT2*polxz + sinT*polyy - 0.5*sin2T*polxx); |
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109 | PHI23 *= 0.5; |
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110 | phi2 = G4ThreeVector(PHI21, PHI22, PHI23); |
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111 | |
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112 | // polarization of outgoing electron |
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113 | G4double PHI32 = -sinT2*polxy + ((1. - eps)/eps)*sinT*polyz + 0.5*(cos2T + 3.)*pol1.y(); |
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114 | PHI32 *= 0.5; |
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115 | |
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116 | G4double PHI31 = 0., PHI31add = 0., PHI33 = 0., PHI33add = 0.; |
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117 | |
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118 | if ((1. - eps) > 1.e-12){ |
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119 | G4double helpVar = std::sqrt(eps2 - 2.*cosT*eps + 1.); |
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120 | |
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121 | PHI31 = (1. - eps)*(1. + cosT)*sinT*pol0.z(); |
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122 | PHI31 += (-eps*cosT3 + eps*cosT2 + (eps - 2.)*cosT + eps)*pol1.x(); |
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123 | PHI31 += -(eps*cosT2 - eps*cosT + cosT + 1.)*sinT*pol1.z(); |
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124 | PHI31 /= 2.*helpVar; |
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125 | |
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126 | PHI31add = -eps*sqr(1. - cosT)*(1. + cosT)*polxx; |
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127 | PHI31add += (1. - eps)*sinT2*polyy; |
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128 | PHI31add += -(-eps2 + cosT*(cosT*eps - eps + 1.)*eps + eps - 1.)*sinT*polxz/eps; |
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129 | PHI31add /= 2.*helpVar; |
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130 | |
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131 | PHI33 = ((1. - eps)/eps)*(-eps*cosT2 + eps*(eps + 1.)*cosT - 1.)*pol0.z(); |
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132 | PHI33 += -(eps*cosT2 + (1. - eps)*eps*cosT + 1.)*sinT*pol1.x(); |
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133 | PHI33 += -(-eps2*cosT3 + eps*(eps2 - eps + 1.)*cosT2 - cosT + eps2)*pol1.z()/eps; |
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134 | PHI33 /= -2.*helpVar; |
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135 | |
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136 | PHI33add = (eps*(eps - cosT - 1.)*cosT + 1.)*sinT*polxx; |
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137 | PHI33add += -(-eps2 + cosT*eps + eps - 1.)*sinT2*polxz; |
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138 | PHI33add += (eps - 1.)*(cosT - eps)*sinT*polyy; |
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139 | PHI33add /= -2.*helpVar; |
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140 | }else{ |
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141 | PHI31 = -pol1.z() - (X - 1.)*std::sqrt(1. - eps)*pol1.x()/std::sqrt(2.*X); |
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142 | PHI31add = -(-X*X*pol1.z() - 2.*X*(2.*pol0.z() - pol1.z()) - (4.*pol0.x() + 5.)*pol1.z())*(1. - eps)/(4.*X); |
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143 | |
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144 | PHI33 = pol1.x() - (X - 1.)*std::sqrt(1. - eps)*pol1.z()/std::sqrt(2.*X); |
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145 | PHI33add = -(X*X - 2.*X + 4.*pol0.x() + 5.)*(1. - eps)*pol1.x()/(4.*X); |
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146 | } |
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147 | phi3 = G4ThreeVector(PHI31 + PHI31add, PHI32, PHI33 + PHI33add); |
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148 | |
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149 | } |
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150 | unpXS *= diffXSFactor; |
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151 | polXS *= diffXSFactor; |
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152 | phi0 *= diffXSFactor; |
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153 | phi2 *= diffXSFactor; |
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154 | phi3 *= diffXSFactor; |
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155 | |
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156 | } |
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157 | |
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158 | G4double G4PolarizedComptonCrossSection::XSection(const G4StokesVector & pol2,const G4StokesVector & pol3) |
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159 | { |
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160 | gammaPol2 = !(pol2==G4StokesVector::ZERO); |
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161 | electronPol3 = !(pol3==G4StokesVector::ZERO); |
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162 | |
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163 | G4double phi = 0.; |
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164 | // polarization independent part |
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165 | phi += phi0; |
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166 | |
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167 | |
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168 | if (gammaPol2) { |
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169 | // part depending on the polarization of the final photon |
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170 | phi += phi2*pol2; |
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171 | } |
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172 | |
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173 | if (electronPol3) { |
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174 | // part depending on the polarization of the final electron |
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175 | phi += phi3*pol3; |
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176 | } |
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177 | |
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178 | // return cross section. |
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179 | return phi; |
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180 | } |
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181 | |
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182 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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183 | |
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184 | |
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185 | G4double G4PolarizedComptonCrossSection::TotalXSection(G4double /*xmin*/, G4double /*xmax*/, G4double k0, |
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186 | const G4StokesVector & pol0, |
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187 | const G4StokesVector & pol1) |
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188 | { |
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189 | |
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190 | // G4double k0 = gammaEnergy / electron_mass_c2 ; |
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191 | G4double k1 = 1 + 2*k0 ; |
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192 | |
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193 | // // pi*re^2 |
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194 | // G4double re=2.81794e-15; //m |
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195 | // G4double barn=1.e-28; //m^2 |
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196 | G4double Z=theZ; |
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197 | |
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198 | G4double unit = Z*pi*classic_electr_radius |
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199 | * classic_electr_radius ; // *1./barn; |
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200 | |
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201 | G4double pre = unit/(sqr(k0)*sqr(1.+2.*k0)); |
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202 | |
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203 | G4double xs_0 = ((k0 - 2.)*k0 -2.)*sqr(k1)*std::log(k1) + 2.*k0*(k0*(k0 + 1.)*(k0 + 8.) + 2.); |
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204 | G4double xs_pol = (k0 + 1.)*sqr(k1)*std::log(k1) - 2.*k0*(5.*sqr(k0) + 4.*k0 + 1.); |
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205 | |
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206 | return pre*(xs_0/k0 + pol0.p3()*pol1.z()*xs_pol); |
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207 | } |
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208 | |
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209 | |
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210 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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211 | |
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212 | |
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213 | G4StokesVector G4PolarizedComptonCrossSection::GetPol2() |
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214 | { |
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215 | // Note, mean polarization can not contain correlation |
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216 | // effects. |
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217 | return 1./phi0 * phi2; |
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218 | } |
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219 | |
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220 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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221 | |
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222 | G4StokesVector G4PolarizedComptonCrossSection::GetPol3() |
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223 | { |
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224 | // Note, mean polarization can not contain correlation |
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225 | // effects. |
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226 | return 1./phi0 * phi3; |
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227 | } |
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228 | |
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229 | |
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230 | |
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231 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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232 | void G4PolarizedComptonCrossSection::DefineCoefficients(const G4StokesVector & pol0, |
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233 | const G4StokesVector & pol1) |
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234 | { |
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235 | polxx=pol0.x()*pol1.x(); |
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236 | polyy=pol0.y()*pol1.y(); |
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237 | polzz=pol0.z()*pol1.z(); |
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238 | |
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239 | polxz=pol0.x()*pol1.z(); |
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240 | polzx=pol0.z()*pol1.x(); |
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241 | |
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242 | polyz=pol0.y()*pol1.z(); |
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243 | polzy=pol0.z()*pol1.y(); |
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244 | |
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245 | polxy=pol0.x()*pol1.y(); |
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246 | polyx=pol0.y()*pol1.x(); |
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247 | } |
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248 | |
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249 | |
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250 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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