1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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13 | // * work make any representation or warranty, express or implied, * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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16 | // * for the full disclaimer and the limitation of liability. * |
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17 | // * * |
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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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20 | // * By using, copying, modifying or distributing the software (or * |
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21 | // * any work based on the software) you agree to acknowledge its * |
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22 | // * use in resulting scientific publications, and indicate your * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4MuPairProductionModel.cc,v 1.44 2009/08/11 16:50:07 vnivanch Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-03 $ |
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28 | // |
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29 | // ------------------------------------------------------------------- |
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30 | // |
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31 | // GEANT4 Class file |
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32 | // |
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33 | // |
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34 | // File name: G4MuPairProductionModel |
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35 | // |
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36 | // Author: Vladimir Ivanchenko on base of Laszlo Urban code |
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37 | // |
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38 | // Creation date: 24.06.2002 |
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39 | // |
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40 | // Modifications: |
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41 | // |
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42 | // 04-12-02 Change G4DynamicParticle constructor in PostStep (V.Ivanchenko) |
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43 | // 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko) |
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44 | // 24-01-03 Fix for compounds (V.Ivanchenko) |
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45 | // 27-01-03 Make models region aware (V.Ivanchenko) |
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46 | // 13-02-03 Add model (V.Ivanchenko) |
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47 | // 06-06-03 Fix in cross section calculation for high energy (V.Ivanchenko) |
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48 | // 20-10-03 2*xi in ComputeDDMicroscopicCrossSection (R.Kokoulin) |
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49 | // 8 integration points in ComputeDMicroscopicCrossSection |
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50 | // 12-01-04 Take min cut of e- and e+ not its sum (V.Ivanchenko) |
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51 | // 10-02-04 Update parameterisation using R.Kokoulin model (V.Ivanchenko) |
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52 | // 28-04-04 For complex materials repeat calculation of max energy for each |
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53 | // material (V.Ivanchenko) |
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54 | // 01-11-04 Fix bug inside ComputeDMicroscopicCrossSection (R.Kokoulin) |
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55 | // 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko) |
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56 | // 03-08-05 Add SetParticle method (V.Ivantchenko) |
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57 | // 23-10-05 Add protection in sampling of e+e- pair energy needed for |
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58 | // low cuts (V.Ivantchenko) |
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59 | // 13-02-06 Add ComputeCrossSectionPerAtom (mma) |
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60 | // 24-04-07 Add protection in SelectRandomAtom method (V.Ivantchenko) |
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61 | // 12-05-06 Updated sampling (use cut) in SelectRandomAtom (A.Bogdanov) |
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62 | // 11-10-07 Add ignoreCut flag (V.Ivanchenko) |
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63 | |
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64 | // |
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65 | // Class Description: |
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66 | // |
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67 | // |
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68 | // ------------------------------------------------------------------- |
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69 | // |
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70 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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71 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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72 | |
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73 | #include "G4MuPairProductionModel.hh" |
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74 | #include "G4Electron.hh" |
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75 | #include "G4Positron.hh" |
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76 | #include "G4MuonMinus.hh" |
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77 | #include "G4MuonPlus.hh" |
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78 | #include "Randomize.hh" |
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79 | #include "G4Material.hh" |
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80 | #include "G4Element.hh" |
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81 | #include "G4ElementVector.hh" |
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82 | #include "G4ProductionCutsTable.hh" |
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83 | #include "G4ParticleChangeForLoss.hh" |
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84 | #include "G4ParticleChangeForGamma.hh" |
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85 | |
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86 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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87 | |
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88 | // static members |
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89 | // |
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90 | G4double G4MuPairProductionModel::zdat[]={1., 4., 13., 29., 92.}; |
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91 | G4double G4MuPairProductionModel::adat[]={1.01, 9.01, 26.98, 63.55, 238.03}; |
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92 | G4double G4MuPairProductionModel::tdat[]={1.e3, 1.e4, 1.e5, 1.e6, 1.e7, 1.e8, |
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93 | 1.e9, 1.e10}; |
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94 | G4double G4MuPairProductionModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083, |
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95 | 0.5917, 0.7628, 0.8983, 0.9801 }; |
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96 | G4double G4MuPairProductionModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813, |
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97 | 0.1813, 0.1569, 0.1112, 0.0506 }; |
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98 | |
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99 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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100 | |
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101 | using namespace std; |
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102 | |
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103 | G4MuPairProductionModel::G4MuPairProductionModel(const G4ParticleDefinition* p, |
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104 | const G4String& nam) |
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105 | : G4VEmModel(nam), |
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106 | particle(0), |
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107 | factorForCross(4.*fine_structure_const*fine_structure_const |
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108 | *classic_electr_radius*classic_electr_radius/(3.*pi)), |
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109 | sqrte(sqrt(exp(1.))), |
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110 | currentZ(0), |
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111 | fParticleChange(0), |
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112 | minPairEnergy(4.*electron_mass_c2), |
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113 | lowestKinEnergy(1.*GeV), |
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114 | nzdat(5), |
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115 | ntdat(8), |
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116 | nbiny(1000), |
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117 | nmaxElements(0), |
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118 | ymin(-5.), |
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119 | ymax(0.), |
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120 | dy((ymax-ymin)/nbiny), |
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121 | samplingTablesAreFilled(false) |
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122 | { |
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123 | SetLowEnergyLimit(minPairEnergy); |
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124 | nist = G4NistManager::Instance(); |
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125 | |
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126 | theElectron = G4Electron::Electron(); |
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127 | thePositron = G4Positron::Positron(); |
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128 | |
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129 | if(p) SetParticle(p); |
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130 | } |
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131 | |
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132 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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133 | |
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134 | G4MuPairProductionModel::~G4MuPairProductionModel() |
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135 | {} |
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136 | |
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137 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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138 | |
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139 | G4double G4MuPairProductionModel::MinEnergyCut(const G4ParticleDefinition*, |
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140 | const G4MaterialCutsCouple* ) |
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141 | { |
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142 | return minPairEnergy; |
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143 | } |
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144 | |
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145 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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146 | |
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147 | G4double G4MuPairProductionModel::MaxSecondaryEnergy(const G4ParticleDefinition*, |
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148 | G4double kineticEnergy) |
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149 | { |
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150 | G4double maxPairEnergy = kineticEnergy + particleMass*(1.0 - 0.75*sqrte*z13); |
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151 | return maxPairEnergy; |
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152 | } |
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153 | |
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154 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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155 | |
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156 | void G4MuPairProductionModel::Initialise(const G4ParticleDefinition* p, |
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157 | const G4DataVector&) |
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158 | { |
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159 | if (!samplingTablesAreFilled) { |
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160 | if(p) SetParticle(p); |
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161 | MakeSamplingTables(); |
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162 | } |
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163 | if(!fParticleChange) fParticleChange = GetParticleChangeForLoss(); |
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164 | } |
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165 | |
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166 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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167 | |
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168 | G4double G4MuPairProductionModel::ComputeDEDXPerVolume( |
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169 | const G4Material* material, |
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170 | const G4ParticleDefinition*, |
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171 | G4double kineticEnergy, |
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172 | G4double cutEnergy) |
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173 | { |
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174 | G4double dedx = 0.0; |
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175 | if (cutEnergy <= minPairEnergy || kineticEnergy <= lowestKinEnergy) |
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176 | return dedx; |
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177 | |
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178 | const G4ElementVector* theElementVector = material->GetElementVector(); |
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179 | const G4double* theAtomicNumDensityVector = |
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180 | material->GetAtomicNumDensityVector(); |
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181 | |
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182 | // loop for elements in the material |
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183 | for (size_t i=0; i<material->GetNumberOfElements(); i++) { |
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184 | G4double Z = (*theElementVector)[i]->GetZ(); |
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185 | SetCurrentElement(Z); |
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186 | G4double tmax = MaxSecondaryEnergy(particle, kineticEnergy); |
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187 | G4double loss = ComputMuPairLoss(Z, kineticEnergy, cutEnergy, tmax); |
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188 | dedx += loss*theAtomicNumDensityVector[i]; |
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189 | } |
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190 | if (dedx < 0.) dedx = 0.; |
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191 | return dedx; |
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192 | } |
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193 | |
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194 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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195 | |
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196 | G4double G4MuPairProductionModel::ComputMuPairLoss(G4double Z, |
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197 | G4double tkin, |
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198 | G4double cutEnergy, |
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199 | G4double tmax) |
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200 | { |
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201 | SetCurrentElement(Z); |
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202 | G4double loss = 0.0; |
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203 | |
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204 | G4double cut = std::min(cutEnergy,tmax); |
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205 | if(cut <= minPairEnergy) return loss; |
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206 | |
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207 | // calculate the rectricted loss |
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208 | // numerical integration in log(PairEnergy) |
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209 | G4double ak1=6.9; |
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210 | G4double ak2=1.0; |
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211 | G4double aaa = log(minPairEnergy); |
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212 | G4double bbb = log(cut); |
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213 | G4int kkk = (G4int)((bbb-aaa)/ak1+ak2); |
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214 | if (kkk > 8) kkk = 8; |
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215 | G4double hhh = (bbb-aaa)/(G4double)kkk; |
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216 | G4double x = aaa; |
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217 | |
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218 | for (G4int l=0 ; l<kkk; l++) |
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219 | { |
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220 | |
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221 | for (G4int ll=0; ll<8; ll++) |
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222 | { |
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223 | G4double ep = exp(x+xgi[ll]*hhh); |
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224 | loss += wgi[ll]*ep*ep*ComputeDMicroscopicCrossSection(tkin, Z, ep); |
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225 | } |
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226 | x += hhh; |
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227 | } |
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228 | loss *= hhh; |
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229 | if (loss < 0.) loss = 0.; |
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230 | return loss; |
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231 | } |
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232 | |
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233 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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234 | |
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235 | G4double G4MuPairProductionModel::ComputeMicroscopicCrossSection( |
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236 | G4double tkin, |
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237 | G4double Z, |
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238 | G4double cut) |
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239 | { |
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240 | G4double cross = 0.; |
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241 | SetCurrentElement(Z); |
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242 | G4double tmax = MaxSecondaryEnergy(particle, tkin); |
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243 | if (tmax <= cut) return cross; |
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244 | |
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245 | G4double ak1=6.9 ; |
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246 | G4double ak2=1.0 ; |
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247 | G4double aaa = log(cut); |
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248 | G4double bbb = log(tmax); |
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249 | G4int kkk = (G4int)((bbb-aaa)/ak1 + ak2); |
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250 | if(kkk > 8) kkk = 8; |
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251 | G4double hhh = (bbb-aaa)/float(kkk); |
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252 | G4double x = aaa; |
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253 | |
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254 | for(G4int l=0; l<kkk; l++) |
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255 | { |
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256 | for(G4int i=0; i<8; i++) |
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257 | { |
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258 | G4double ep = exp(x + xgi[i]*hhh); |
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259 | cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep); |
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260 | } |
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261 | x += hhh; |
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262 | } |
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263 | |
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264 | cross *=hhh; |
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265 | if(cross < 0.0) cross = 0.0; |
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266 | return cross; |
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267 | } |
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268 | |
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269 | G4double G4MuPairProductionModel::ComputeDMicroscopicCrossSection( |
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270 | G4double tkin, |
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271 | G4double Z, |
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272 | G4double pairEnergy) |
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273 | // Calculates the differential (D) microscopic cross section |
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274 | // using the cross section formula of R.P. Kokoulin (18/01/98) |
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275 | // Code modified by R.P. Kokoulin, V.N. Ivanchenko (27/01/04) |
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276 | { |
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277 | G4double bbbtf= 183. ; |
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278 | G4double bbbh = 202.4 ; |
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279 | G4double g1tf = 1.95e-5 ; |
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280 | G4double g2tf = 5.3e-5 ; |
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281 | G4double g1h = 4.4e-5 ; |
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282 | G4double g2h = 4.8e-5 ; |
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283 | |
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284 | G4double totalEnergy = tkin + particleMass; |
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285 | G4double residEnergy = totalEnergy - pairEnergy; |
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286 | G4double massratio = particleMass/electron_mass_c2 ; |
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287 | G4double massratio2 = massratio*massratio ; |
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288 | G4double cross = 0.; |
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289 | |
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290 | SetCurrentElement(Z); |
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291 | |
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292 | G4double c3 = 0.75*sqrte*particleMass; |
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293 | if (residEnergy <= c3*z13) return cross; |
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294 | |
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295 | G4double c7 = 4.*electron_mass_c2; |
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296 | G4double c8 = 6.*particleMass*particleMass; |
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297 | G4double alf = c7/pairEnergy; |
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298 | G4double a3 = 1. - alf; |
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299 | if (a3 <= 0.) return cross; |
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300 | |
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301 | // zeta calculation |
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302 | G4double bbb,g1,g2; |
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303 | if( Z < 1.5 ) { bbb = bbbh ; g1 = g1h ; g2 = g2h ; } |
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304 | else { bbb = bbbtf; g1 = g1tf; g2 = g2tf; } |
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305 | |
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306 | G4double zeta = 0; |
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307 | G4double zeta1 = 0.073*log(totalEnergy/(particleMass+g1*z23*totalEnergy))-0.26; |
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308 | if ( zeta1 > 0.) |
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309 | { |
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310 | G4double zeta2 = 0.058*log(totalEnergy/(particleMass+g2*z13*totalEnergy))-0.14; |
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311 | zeta = zeta1/zeta2 ; |
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312 | } |
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313 | |
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314 | G4double z2 = Z*(Z+zeta); |
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315 | G4double screen0 = 2.*electron_mass_c2*sqrte*bbb/(z13*pairEnergy); |
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316 | G4double a0 = totalEnergy*residEnergy; |
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317 | G4double a1 = pairEnergy*pairEnergy/a0; |
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318 | G4double bet = 0.5*a1; |
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319 | G4double xi0 = 0.25*massratio2*a1; |
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320 | G4double del = c8/a0; |
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321 | |
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322 | G4double rta3 = sqrt(a3); |
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323 | G4double tmnexp = alf/(1. + rta3) + del*rta3; |
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324 | if(tmnexp >= 1.0) return cross; |
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325 | |
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326 | G4double tmn = log(tmnexp); |
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327 | G4double sum = 0.; |
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328 | |
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329 | // Gaussian integration in ln(1-ro) ( with 8 points) |
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330 | for (G4int i=0; i<8; i++) |
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331 | { |
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332 | G4double a4 = exp(tmn*xgi[i]); // a4 = (1.-asymmetry) |
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333 | G4double a5 = a4*(2.-a4) ; |
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334 | G4double a6 = 1.-a5 ; |
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335 | G4double a7 = 1.+a6 ; |
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336 | G4double a9 = 3.+a6 ; |
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337 | G4double xi = xi0*a5 ; |
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338 | G4double xii = 1./xi ; |
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339 | G4double xi1 = 1.+xi ; |
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340 | G4double screen = screen0*xi1/a5 ; |
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341 | G4double yeu = 5.-a6+4.*bet*a7 ; |
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342 | G4double yed = 2.*(1.+3.*bet)*log(3.+xii)-a6-a1*(2.-a6) ; |
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343 | G4double ye1 = 1.+yeu/yed ; |
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344 | G4double ale=log(bbb/z13*sqrt(xi1*ye1)/(1.+screen*ye1)) ; |
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345 | G4double cre = 0.5*log(1.+2.25*z23*xi1*ye1/massratio2) ; |
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346 | G4double be; |
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347 | |
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348 | if (xi <= 1.e3) be = ((2.+a6)*(1.+bet)+xi*a9)*log(1.+xii)+(a5-bet)/xi1-a9; |
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349 | else be = (3.-a6+a1*a7)/(2.*xi); |
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350 | |
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351 | G4double fe = (ale-cre)*be; |
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352 | if ( fe < 0.) fe = 0. ; |
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353 | |
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354 | G4double ymu = 4.+a6 +3.*bet*a7 ; |
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355 | G4double ymd = a7*(1.5+a1)*log(3.+xi)+1.-1.5*a6 ; |
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356 | G4double ym1 = 1.+ymu/ymd ; |
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357 | G4double alm_crm = log(bbb*massratio/(1.5*z23*(1.+screen*ym1))); |
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358 | G4double a10,bm; |
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359 | if ( xi >= 1.e-3) |
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360 | { |
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361 | a10 = (1.+a1)*a5 ; |
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362 | bm = (a7*(1.+1.5*bet)-a10*xii)*log(xi1)+xi*(a5-bet)/xi1+a10; |
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363 | } else { |
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364 | bm = (5.-a6+bet*a9)*(xi/2.); |
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365 | } |
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366 | |
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367 | G4double fm = alm_crm*bm; |
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368 | if ( fm < 0.) fm = 0. ; |
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369 | |
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370 | sum += wgi[i]*a4*(fe+fm/massratio2); |
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371 | } |
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372 | |
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373 | cross = -tmn*sum*factorForCross*z2*residEnergy/(totalEnergy*pairEnergy); |
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374 | |
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375 | return cross; |
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376 | } |
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377 | |
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378 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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379 | |
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380 | G4double G4MuPairProductionModel::ComputeCrossSectionPerAtom( |
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381 | const G4ParticleDefinition*, |
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382 | G4double kineticEnergy, |
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383 | G4double Z, G4double, |
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384 | G4double cutEnergy, |
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385 | G4double maxEnergy) |
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386 | { |
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387 | G4double cross = 0.0; |
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388 | if (kineticEnergy <= lowestKinEnergy) return cross; |
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389 | |
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390 | SetCurrentElement(Z); |
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391 | |
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392 | G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy); |
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393 | G4double tmax = std::min(maxEnergy, maxPairEnergy); |
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394 | G4double cut = std::max(cutEnergy, minPairEnergy); |
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395 | if (cut >= tmax) return cross; |
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396 | |
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397 | cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut); |
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398 | if(tmax < kineticEnergy) { |
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399 | cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax); |
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400 | } |
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401 | return cross; |
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402 | } |
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403 | |
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404 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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405 | |
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406 | void G4MuPairProductionModel::MakeSamplingTables() |
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407 | { |
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408 | for (G4int iz=0; iz<nzdat; iz++) |
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409 | { |
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410 | G4double Z = zdat[iz]; |
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411 | SetCurrentElement(Z); |
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412 | |
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413 | for (G4int it=0; it<ntdat; it++) { |
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414 | |
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415 | G4double kineticEnergy = tdat[it]; |
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416 | G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy); |
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417 | // G4cout << "Z= " << currentZ << " z13= " << z13 |
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418 | //<< " mE= " << maxPairEnergy << G4endl; |
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419 | G4double CrossSection = 0.0 ; |
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420 | |
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421 | if(maxPairEnergy > minPairEnergy) { |
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422 | |
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423 | G4double y = ymin - 0.5*dy ; |
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424 | G4double yy = ymin - dy ; |
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425 | G4double x = exp(y); |
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426 | G4double fac = exp(dy); |
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427 | G4double dx = exp(yy)*(fac - 1.0); |
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428 | |
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429 | G4double c = log(maxPairEnergy/minPairEnergy); |
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430 | |
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431 | for (G4int i=0 ; i<nbiny; i++) { |
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432 | y += dy ; |
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433 | if(c > 0.0) { |
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434 | x *= fac; |
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435 | dx*= fac; |
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436 | G4double ep = minPairEnergy*exp(c*x) ; |
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437 | CrossSection += |
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438 | ep*dx*ComputeDMicroscopicCrossSection(kineticEnergy, Z, ep); |
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439 | } |
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440 | ya[i] = y; |
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441 | proba[iz][it][i] = CrossSection; |
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442 | } |
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443 | |
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444 | } else { |
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445 | for (G4int i=0 ; i<nbiny; i++) { |
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446 | proba[iz][it][i] = CrossSection; |
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447 | } |
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448 | } |
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449 | |
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450 | ya[nbiny]=ymax; |
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451 | proba[iz][it][nbiny] = CrossSection; |
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452 | |
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453 | } |
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454 | } |
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455 | samplingTablesAreFilled = true; |
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456 | } |
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457 | |
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458 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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459 | |
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460 | void |
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461 | G4MuPairProductionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp, |
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462 | const G4MaterialCutsCouple* couple, |
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463 | const G4DynamicParticle* aDynamicParticle, |
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464 | G4double tmin, |
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465 | G4double tmax) |
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466 | { |
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467 | G4double kineticEnergy = aDynamicParticle->GetKineticEnergy(); |
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468 | G4double totalEnergy = kineticEnergy + particleMass ; |
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469 | G4ParticleMomentum ParticleDirection = |
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470 | aDynamicParticle->GetMomentumDirection(); |
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471 | |
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472 | G4int it; |
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473 | for(it=1; it<ntdat; it++) {if(kineticEnergy <= tdat[it]) break;} |
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474 | if(it == ntdat) it--; |
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475 | G4double dt = log(kineticEnergy/tdat[it-1])/log(tdat[it]/tdat[it-1]); |
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476 | |
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477 | // select randomly one element constituing the material |
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478 | const G4Element* anElement = SelectRandomAtom(kineticEnergy, dt, it, couple, tmin); |
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479 | SetCurrentElement(anElement->GetZ()); |
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480 | |
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481 | // define interval of enegry transfer |
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482 | G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy); |
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483 | G4double maxEnergy = std::min(tmax, maxPairEnergy); |
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484 | G4double minEnergy = std::max(tmin, minPairEnergy); |
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485 | |
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486 | if(minEnergy >= maxEnergy) return; |
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487 | //G4cout << "emin= " << minEnergy << " emax= " << maxEnergy |
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488 | // << " minPair= " << minPairEnergy << " maxpair= " << maxPairEnergy |
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489 | // << " ymin= " << ymin << " dy= " << dy << G4endl; |
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490 | |
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491 | // select bins |
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492 | G4int iymin = 0; |
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493 | G4int iymax = nbiny-1; |
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494 | if( minEnergy > minPairEnergy) |
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495 | { |
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496 | G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy); |
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497 | iymin = (G4int)((log(xc) - ymin)/dy); |
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498 | if(iymin >= nbiny) iymin = nbiny-1; |
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499 | else if(iymin < 0) iymin = 0; |
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500 | xc = log(maxEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy); |
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501 | iymax = (G4int)((log(xc) - ymin)/dy) + 1; |
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502 | if(iymax >= nbiny) iymax = nbiny-1; |
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503 | else if(iymax < 0) iymax = 0; |
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504 | } |
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505 | |
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506 | // sample e-e+ energy, pair energy first |
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507 | G4int iz, iy; |
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508 | |
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509 | for(iz=1; iz<nzdat; iz++) {if(currentZ <= zdat[iz]) break;} |
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510 | if(iz == nzdat) iz--; |
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511 | |
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512 | G4double dz = log(currentZ/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]); |
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513 | |
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514 | G4double pmin = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymin,currentZ); |
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515 | G4double pmax = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymax,currentZ); |
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516 | |
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517 | G4double p = pmin+G4UniformRand()*(pmax - pmin); |
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518 | |
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519 | // interpolate sampling vector; |
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520 | G4double p1 = pmin; |
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521 | G4double p2 = pmin; |
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522 | for(iy=iymin+1; iy<=iymax; iy++) { |
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523 | p1 = p2; |
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524 | p2 = InterpolatedIntegralCrossSection(dt, dz, iz, it, iy, currentZ); |
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525 | if(p <= p2) break; |
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526 | } |
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527 | // G4cout << "iy= " << iy << " iymin= " << iymin << " iymax= " |
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528 | // << iymax << " Z= " << currentZ << G4endl; |
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529 | G4double y = ya[iy-1] + dy*(p - p1)/(p2 - p1); |
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530 | |
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531 | G4double PairEnergy = minPairEnergy*exp(exp(y) |
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532 | *log(maxPairEnergy/minPairEnergy)); |
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533 | |
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534 | if(PairEnergy < minEnergy) PairEnergy = minEnergy; |
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535 | if(PairEnergy > maxEnergy) PairEnergy = maxEnergy; |
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536 | |
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537 | // sample r=(E+-E-)/PairEnergy ( uniformly .....) |
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538 | G4double rmax = |
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539 | (1.-6.*particleMass*particleMass/(totalEnergy*(totalEnergy-PairEnergy))) |
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540 | *sqrt(1.-minPairEnergy/PairEnergy); |
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541 | G4double r = rmax * (-1.+2.*G4UniformRand()) ; |
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542 | |
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543 | // compute energies from PairEnergy,r |
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544 | G4double ElectronEnergy = (1.-r)*PairEnergy*0.5; |
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545 | G4double PositronEnergy = PairEnergy - ElectronEnergy; |
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546 | |
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547 | // angles of the emitted particles ( Z - axis along the parent particle) |
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548 | // (mean theta for the moment) |
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549 | |
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550 | // |
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551 | // scattered electron (positron) angles. ( Z - axis along the parent photon) |
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552 | // |
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553 | // universal distribution suggested by L. Urban |
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554 | // (Geant3 manual (1993) Phys211), |
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555 | // derived from Tsai distribution (Rev Mod Phys 49,421(1977)) |
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556 | // G4cout << "Ee= " << ElectronEnergy << " Ep= " << PositronEnergy << G4endl; |
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557 | G4double u; |
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558 | const G4double a1 = 0.625 , a2 = 3.*a1 , d = 27. ; |
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559 | |
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560 | if (9./(9.+d) >G4UniformRand()) u= - log(G4UniformRand()*G4UniformRand())/a1; |
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561 | else u= - log(G4UniformRand()*G4UniformRand())/a2; |
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562 | |
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563 | G4double TetEl = u*electron_mass_c2/ElectronEnergy; |
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564 | G4double TetPo = u*electron_mass_c2/PositronEnergy; |
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565 | G4double Phi = twopi * G4UniformRand(); |
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566 | G4double dxEl= sin(TetEl)*cos(Phi),dyEl= sin(TetEl)*sin(Phi),dzEl=cos(TetEl); |
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567 | G4double dxPo=-sin(TetPo)*cos(Phi),dyPo=-sin(TetPo)*sin(Phi),dzPo=cos(TetPo); |
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568 | |
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569 | G4ThreeVector ElectDirection (dxEl, dyEl, dzEl); |
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570 | ElectDirection.rotateUz(ParticleDirection); |
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571 | |
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572 | // create G4DynamicParticle object for the particle1 |
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573 | G4DynamicParticle* aParticle1= new G4DynamicParticle(theElectron, |
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574 | ElectDirection, |
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575 | ElectronEnergy - electron_mass_c2); |
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576 | |
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577 | G4ThreeVector PositDirection (dxPo, dyPo, dzPo); |
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578 | PositDirection.rotateUz(ParticleDirection); |
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579 | |
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580 | // create G4DynamicParticle object for the particle2 |
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581 | G4DynamicParticle* aParticle2 = |
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582 | new G4DynamicParticle(thePositron, |
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583 | PositDirection, |
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584 | PositronEnergy - electron_mass_c2); |
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585 | |
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586 | // primary change |
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587 | kineticEnergy -= (ElectronEnergy + PositronEnergy); |
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588 | fParticleChange->SetProposedKineticEnergy(kineticEnergy); |
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589 | |
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590 | vdp->push_back(aParticle1); |
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591 | vdp->push_back(aParticle2); |
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592 | } |
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593 | |
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594 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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595 | |
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596 | const G4Element* G4MuPairProductionModel::SelectRandomAtom( |
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597 | G4double kinEnergy, G4double dt, G4int it, |
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598 | const G4MaterialCutsCouple* couple, G4double tmin) |
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599 | { |
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600 | // select randomly 1 element within the material |
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601 | |
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602 | const G4Material* material = couple->GetMaterial(); |
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603 | size_t nElements = material->GetNumberOfElements(); |
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604 | const G4ElementVector* theElementVector = material->GetElementVector(); |
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605 | if (nElements == 1) return (*theElementVector)[0]; |
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606 | |
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607 | if(nElements > nmaxElements) { |
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608 | nmaxElements = nElements; |
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609 | partialSum.resize(nmaxElements); |
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610 | } |
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611 | |
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612 | const G4double* theAtomNumDensityVector=material->GetAtomicNumDensityVector(); |
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613 | |
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614 | G4double sum = 0.0; |
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615 | G4double dl; |
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616 | |
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617 | size_t i; |
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618 | for (i=0; i<nElements; i++) { |
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619 | G4double Z = ((*theElementVector)[i])->GetZ(); |
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620 | SetCurrentElement(Z); |
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621 | G4double maxPairEnergy = MaxSecondaryEnergy(particle,kinEnergy); |
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622 | G4double minEnergy = std::max(tmin, minPairEnergy); |
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623 | dl = 0.0; |
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624 | if(minEnergy < maxPairEnergy) { |
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625 | |
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626 | G4int iz; |
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627 | for(iz=1; iz<nzdat; iz++) {if(Z <= zdat[iz]) break;} |
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628 | if(iz == nzdat) iz--; |
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629 | G4double dz = log(Z/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]); |
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630 | |
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631 | G4double sigcut; |
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632 | if(minEnergy <= minPairEnergy) |
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633 | sigcut = 0.; |
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634 | else |
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635 | { |
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636 | G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy); |
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637 | G4int iy = (G4int)((log(xc) - ymin)/dy); |
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638 | if(iy < 0) iy = 0; |
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639 | if(iy >= nbiny) iy = nbiny-1; |
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640 | sigcut = InterpolatedIntegralCrossSection(dt,dz,iz,it,iy, Z); |
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641 | } |
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642 | |
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643 | G4double sigtot = InterpolatedIntegralCrossSection(dt,dz,iz,it,nbiny,Z); |
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644 | dl = (sigtot - sigcut)*theAtomNumDensityVector[i]; |
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645 | } |
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646 | // protection |
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647 | if(dl < 0.0) dl = 0.0; |
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648 | sum += dl; |
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649 | partialSum[i] = sum; |
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650 | } |
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651 | |
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652 | G4double rval = G4UniformRand()*sum; |
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653 | for (i=0; i<nElements; i++) { |
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654 | if(rval<=partialSum[i]) return (*theElementVector)[i]; |
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655 | } |
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656 | |
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657 | return (*theElementVector)[nElements - 1]; |
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658 | |
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659 | } |
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660 | |
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661 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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662 | |
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663 | |
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