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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4MollerBhabhaModel.cc,v 1.30 2007/05/22 17:34:36 vnivanch Exp $ |
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27 | // GEANT4 tag $Name: $ |
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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: G4MollerBhabhaModel |
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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: 03.01.2002 |
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39 | // |
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40 | // Modifications: |
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41 | // |
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42 | // 13-11-02 Minor fix - use normalised direction (V.Ivanchenko) |
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43 | // 04-12-02 Change G4DynamicParticle constructor in PostStepDoIt (V.Ivanchenko) |
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44 | // 23-12-02 Change interface in order to move to cut per region (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 name (V.Ivanchenko) |
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47 | // 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko) |
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48 | // 25-07-05 Add protection in calculation of recoil direction for the case |
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49 | // of complete energy transfer from e+ to e- (V.Ivanchenko) |
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50 | // 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma) |
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51 | // 15-05-06 Fix MinEnergyCut (V.Ivanchenko) |
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52 | // |
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53 | // |
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54 | // Class Description: |
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55 | // |
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56 | // Implementation of energy loss and delta-electron production by e+/e- |
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57 | // |
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58 | // ------------------------------------------------------------------- |
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59 | // |
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60 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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61 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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62 | |
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63 | #include "G4MollerBhabhaModel.hh" |
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64 | #include "G4Electron.hh" |
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65 | #include "G4Positron.hh" |
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66 | #include "Randomize.hh" |
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67 | #include "G4ParticleChangeForLoss.hh" |
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68 | |
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69 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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70 | |
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71 | using namespace std; |
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72 | |
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73 | G4MollerBhabhaModel::G4MollerBhabhaModel(const G4ParticleDefinition* p, |
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74 | const G4String& nam) |
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75 | : G4VEmModel(nam), |
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76 | particle(0), |
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77 | isElectron(true), |
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78 | twoln10(2.0*log(10.0)), |
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79 | lowLimit(0.2*keV) |
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80 | { |
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81 | theElectron = G4Electron::Electron(); |
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82 | if(p) SetParticle(p); |
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83 | } |
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84 | |
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85 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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86 | |
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87 | G4MollerBhabhaModel::~G4MollerBhabhaModel() |
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88 | {} |
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89 | |
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90 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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91 | |
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92 | void G4MollerBhabhaModel::SetParticle(const G4ParticleDefinition* p) |
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93 | { |
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94 | particle = p; |
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95 | if(p != theElectron) isElectron = false; |
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96 | } |
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97 | |
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98 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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99 | |
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100 | G4double G4MollerBhabhaModel::MinEnergyCut(const G4ParticleDefinition*, |
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101 | const G4MaterialCutsCouple* couple) |
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102 | { |
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103 | G4double electronDensity = couple->GetMaterial()->GetElectronDensity(); |
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104 | G4double Zeff = electronDensity/couple->GetMaterial()->GetTotNbOfAtomsPerVolume(); |
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105 | return 0.25*sqrt(Zeff)*keV; |
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106 | } |
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107 | |
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108 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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109 | |
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110 | void G4MollerBhabhaModel::Initialise(const G4ParticleDefinition* p, |
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111 | const G4DataVector&) |
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112 | { |
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113 | if(!particle) SetParticle(p); |
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114 | if(pParticleChange) |
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115 | fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*> |
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116 | (pParticleChange); |
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117 | else |
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118 | fParticleChange = new G4ParticleChangeForLoss(); |
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119 | } |
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120 | |
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121 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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122 | |
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123 | G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron( |
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124 | const G4ParticleDefinition* p, |
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125 | G4double kineticEnergy, |
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126 | G4double cutEnergy, |
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127 | G4double maxEnergy) |
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128 | { |
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129 | if(!particle) SetParticle(p); |
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130 | |
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131 | G4double cross = 0.0; |
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132 | G4double tmax = MaxSecondaryEnergy(p, kineticEnergy); |
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133 | tmax = min(maxEnergy, tmax); |
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134 | |
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135 | if(cutEnergy < tmax) { |
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136 | |
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137 | G4double xmin = cutEnergy/kineticEnergy; |
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138 | G4double xmax = tmax/kineticEnergy; |
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139 | G4double gam = kineticEnergy/electron_mass_c2 + 1.0; |
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140 | G4double gamma2= gam*gam; |
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141 | G4double beta2 = 1.0 - 1.0/gamma2; |
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142 | |
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143 | //Moller (e-e-) scattering |
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144 | if (isElectron) { |
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145 | |
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146 | G4double g = (2.0*gam - 1.0)/gamma2; |
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147 | cross = ((xmax - xmin)*(1.0 - g + 1.0/(xmin*xmax) |
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148 | + 1.0/((1.0-xmin)*(1.0 - xmax))) |
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149 | - g*log( xmax*(1.0 - xmin)/(xmin*(1.0 - xmax)) ) ) / beta2; |
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150 | |
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151 | //Bhabha (e+e-) scattering |
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152 | } else { |
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153 | |
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154 | G4double y = 1.0/(1.0 + gam); |
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155 | G4double y2 = y*y; |
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156 | G4double y12 = 1.0 - 2.0*y; |
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157 | G4double b1 = 2.0 - y2; |
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158 | G4double b2 = y12*(3.0 + y2); |
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159 | G4double y122= y12*y12; |
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160 | G4double b4 = y122*y12; |
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161 | G4double b3 = b4 + y122; |
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162 | |
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163 | cross = (xmax - xmin)*(1.0/(beta2*xmin*xmax) + b2 |
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164 | - 0.5*b3*(xmin + xmax) |
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165 | + b4*(xmin*xmin + xmin*xmax + xmax*xmax)/3.0) |
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166 | - b1*log(xmax/xmin); |
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167 | } |
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168 | |
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169 | cross *= twopi_mc2_rcl2/kineticEnergy; |
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170 | } |
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171 | return cross; |
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172 | } |
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173 | |
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174 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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175 | |
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176 | G4double G4MollerBhabhaModel::ComputeCrossSectionPerAtom( |
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177 | const G4ParticleDefinition* p, |
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178 | G4double kineticEnergy, |
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179 | G4double Z, G4double, |
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180 | G4double cutEnergy, |
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181 | G4double maxEnergy) |
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182 | { |
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183 | G4double cross = Z*ComputeCrossSectionPerElectron |
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184 | (p,kineticEnergy,cutEnergy,maxEnergy); |
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185 | return cross; |
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186 | } |
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187 | |
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188 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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189 | |
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190 | G4double G4MollerBhabhaModel::CrossSectionPerVolume( |
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191 | const G4Material* material, |
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192 | const G4ParticleDefinition* p, |
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193 | G4double kineticEnergy, |
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194 | G4double cutEnergy, |
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195 | G4double maxEnergy) |
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196 | { |
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197 | G4double eDensity = material->GetElectronDensity(); |
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198 | G4double cross = eDensity*ComputeCrossSectionPerElectron |
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199 | (p,kineticEnergy,cutEnergy,maxEnergy); |
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200 | return cross; |
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201 | } |
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202 | |
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203 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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204 | |
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205 | G4double G4MollerBhabhaModel::ComputeDEDXPerVolume( |
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206 | const G4Material* material, |
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207 | const G4ParticleDefinition* p, |
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208 | G4double kineticEnergy, |
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209 | G4double cutEnergy) |
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210 | { |
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211 | if(!particle) SetParticle(p); |
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212 | // calculate the dE/dx due to the ionization by Seltzer-Berger formula |
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213 | |
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214 | G4double electronDensity = material->GetElectronDensity(); |
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215 | G4double Zeff = electronDensity/material->GetTotNbOfAtomsPerVolume(); |
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216 | G4double th = 0.25*sqrt(Zeff)*keV; |
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217 | G4double tkin = kineticEnergy; |
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218 | G4bool lowEnergy = false; |
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219 | if (kineticEnergy < th) { |
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220 | tkin = th; |
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221 | lowEnergy = true; |
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222 | } |
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223 | G4double tau = tkin/electron_mass_c2; |
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224 | G4double gam = tau + 1.0; |
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225 | G4double gamma2= gam*gam; |
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226 | G4double beta2 = 1. - 1./gamma2; |
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227 | G4double bg2 = beta2*gamma2; |
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228 | |
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229 | G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy(); |
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230 | eexc /= electron_mass_c2; |
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231 | G4double eexc2 = eexc*eexc; |
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232 | |
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233 | G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2; |
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234 | G4double dedx; |
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235 | |
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236 | // electron |
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237 | if (isElectron) { |
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238 | |
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239 | dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2 |
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240 | + log((tau-d)*d) + tau/(tau-d) |
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241 | + (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2; |
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242 | |
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243 | //positron |
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244 | } else { |
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245 | |
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246 | G4double d2 = d*d*0.5; |
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247 | G4double d3 = d2*d/1.5; |
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248 | G4double d4 = d3*d*3.75; |
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249 | G4double y = 1.0/(1.0 + gam); |
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250 | dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d) |
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251 | - beta2*(tau + 2.0*d - y*(3.0*d2 |
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252 | + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau; |
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253 | } |
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254 | |
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255 | //density correction |
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256 | G4double cden = material->GetIonisation()->GetCdensity(); |
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257 | G4double mden = material->GetIonisation()->GetMdensity(); |
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258 | G4double aden = material->GetIonisation()->GetAdensity(); |
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259 | G4double x0den = material->GetIonisation()->GetX0density(); |
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260 | G4double x1den = material->GetIonisation()->GetX1density(); |
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261 | G4double x = log(bg2)/twoln10; |
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262 | |
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263 | if (x >= x0den) { |
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264 | dedx -= twoln10*x - cden; |
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265 | if (x < x1den) dedx -= aden*pow(x1den-x, mden); |
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266 | } |
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267 | |
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268 | // now you can compute the total ionization loss |
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269 | dedx *= twopi_mc2_rcl2*electronDensity/beta2; |
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270 | if (dedx < 0.0) dedx = 0.0; |
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271 | |
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272 | // lowenergy extrapolation |
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273 | |
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274 | if (lowEnergy) { |
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275 | |
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276 | if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy); |
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277 | else dedx *= sqrt(tkin*kineticEnergy)/lowLimit; |
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278 | |
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279 | } |
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280 | return dedx; |
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281 | } |
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282 | |
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283 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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284 | |
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285 | void G4MollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp, |
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286 | const G4MaterialCutsCouple*, |
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287 | const G4DynamicParticle* dp, |
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288 | G4double tmin, |
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289 | G4double maxEnergy) |
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290 | { |
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291 | G4double tmax = std::min(maxEnergy, MaxSecondaryKinEnergy(dp)); |
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292 | if(tmin >= tmax) return; |
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293 | |
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294 | G4double kineticEnergy = dp->GetKineticEnergy(); |
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295 | G4double energy = kineticEnergy + electron_mass_c2; |
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296 | G4double totalMomentum = sqrt(kineticEnergy*(energy + electron_mass_c2)); |
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297 | G4double xmin = tmin/kineticEnergy; |
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298 | G4double xmax = tmax/kineticEnergy; |
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299 | G4double gam = energy/electron_mass_c2; |
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300 | G4double gamma2 = gam*gam; |
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301 | G4double beta2 = 1.0 - 1.0/gamma2; |
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302 | G4double x, z, q, grej; |
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303 | |
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304 | G4ThreeVector direction = dp->GetMomentumDirection(); |
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305 | |
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306 | //Moller (e-e-) scattering |
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307 | if (isElectron) { |
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308 | |
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309 | G4double g = (2.0*gam - 1.0)/gamma2; |
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310 | G4double y = 1.0 - xmax; |
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311 | grej = 1.0 - g*xmax + xmax*xmax*(1.0 - g + (1.0 - g*y)/(y*y)); |
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312 | |
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313 | do { |
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314 | q = G4UniformRand(); |
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315 | x = xmin*xmax/(xmin*(1.0 - q) + xmax*q); |
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316 | y = 1.0 - x; |
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317 | z = 1.0 - g*x + x*x*(1.0 - g + (1.0 - g*y)/(y*y)); |
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318 | /* |
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319 | if(z > grej) { |
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320 | G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! " |
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321 | << "Majorant " << grej << " < " |
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322 | << z << " for x= " << x |
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323 | << " e-e- scattering" |
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324 | << G4endl; |
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325 | } |
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326 | */ |
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327 | } while(grej * G4UniformRand() > z); |
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328 | |
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329 | //Bhabha (e+e-) scattering |
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330 | } else { |
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331 | |
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332 | G4double y = 1.0/(1.0 + gam); |
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333 | G4double y2 = y*y; |
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334 | G4double y12 = 1.0 - 2.0*y; |
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335 | G4double b1 = 2.0 - y2; |
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336 | G4double b2 = y12*(3.0 + y2); |
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337 | G4double y122= y12*y12; |
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338 | G4double b4 = y122*y12; |
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339 | G4double b3 = b4 + y122; |
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340 | |
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341 | y = xmax*xmax; |
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342 | grej = -xmin*b1; |
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343 | grej += y*b2; |
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344 | grej -= xmin*xmin*xmin*b3; |
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345 | grej += y*y*b4; |
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346 | grej *= beta2; |
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347 | grej += 1.0; |
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348 | do { |
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349 | q = G4UniformRand(); |
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350 | x = xmin*xmax/(xmin*(1.0 - q) + xmax*q); |
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351 | z = -x*b1; |
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352 | y = x*x; |
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353 | z += y*b2; |
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354 | y *= x; |
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355 | z -= y*b3; |
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356 | y *= x; |
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357 | z += y*b4; |
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358 | z *= beta2; |
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359 | z += 1.0; |
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360 | /* |
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361 | if(z > grej) { |
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362 | G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! " |
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363 | << "Majorant " << grej << " < " |
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364 | << z << " for x= " << x |
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365 | << " e+e- scattering" |
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366 | << G4endl; |
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367 | } |
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368 | */ |
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369 | } while(grej * G4UniformRand() > z); |
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370 | } |
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371 | |
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372 | G4double deltaKinEnergy = x * kineticEnergy; |
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373 | |
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374 | G4double deltaMomentum = |
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375 | sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2)); |
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376 | G4double cost = deltaKinEnergy * (energy + electron_mass_c2) / |
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377 | (deltaMomentum * totalMomentum); |
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378 | G4double sint = 1.0 - cost*cost; |
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379 | if(sint > 0.0) sint = sqrt(sint); |
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380 | |
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381 | G4double phi = twopi * G4UniformRand() ; |
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382 | |
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383 | G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ; |
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384 | deltaDirection.rotateUz(direction); |
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385 | |
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386 | // primary change |
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387 | kineticEnergy -= deltaKinEnergy; |
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388 | fParticleChange->SetProposedKineticEnergy(kineticEnergy); |
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389 | |
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390 | if(kineticEnergy > DBL_MIN) { |
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391 | G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection; |
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392 | direction = dir.unit(); |
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393 | fParticleChange->SetProposedMomentumDirection(direction); |
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394 | } |
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395 | |
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396 | // create G4DynamicParticle object for delta ray |
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397 | G4DynamicParticle* delta = new G4DynamicParticle(theElectron, |
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398 | deltaDirection,deltaKinEnergy); |
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399 | vdp->push_back(delta); |
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400 | } |
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401 | |
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402 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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