1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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7 | // * conditions of the Geant4 Software License, included in the file * |
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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 | // |
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27 | // $Id: G4FinalStateElasticScreenedRutherford.cc,v 1.2 2007/10/12 23:10:33 pia Exp $ |
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28 | // GEANT4 tag $Name: $ |
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29 | // |
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30 | // Contact Author: Maria Grazia Pia (Maria.Grazia.Pia@cern.ch) |
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31 | // |
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32 | // Reference: TNS Geant4-DNA paper |
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33 | // Reference for implementation model: NIM. 155, pp. 145-156, 1978 |
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34 | |
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35 | // History: |
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36 | // ----------- |
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37 | // Date Name Modification |
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38 | // 28 Apr 2007 M.G. Pia Created in compliance with design described in TNS paper |
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39 | // |
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40 | // ------------------------------------------------------------------- |
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41 | |
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42 | // Class description: |
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43 | // Reference: TNS Geant4-DNA paper |
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44 | // S. Chauvie et al., Geant4 physics processes for microdosimetry simulation: |
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45 | // design foundation and implementation of the first set of models, |
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46 | // IEEE Trans. Nucl. Sci., vol. 54, no. 6, Dec. 2007. |
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47 | // Further documentation available from http://www.ge.infn.it/geant4/dna |
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48 | |
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49 | // ------------------------------------------------------------------- |
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50 | |
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51 | |
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52 | #include "G4FinalStateElasticScreenedRutherford.hh" |
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53 | #include "G4Track.hh" |
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54 | #include "G4Step.hh" |
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55 | #include "G4DynamicParticle.hh" |
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56 | #include "Randomize.hh" |
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57 | |
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58 | #include "G4ParticleTypes.hh" |
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59 | #include "G4ParticleDefinition.hh" |
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60 | #include "G4Electron.hh" |
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61 | #include "G4SystemOfUnits.hh" |
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62 | #include "G4ParticleMomentum.hh" |
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63 | |
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64 | G4FinalStateElasticScreenedRutherford::G4FinalStateElasticScreenedRutherford() |
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65 | { |
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66 | // These data members will be used in the next implementation iteration, |
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67 | // when the enriched PhysicsModel policy is implemented |
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68 | name = "FinalStateElasticScreenedRutherford"; |
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69 | lowEnergyLimit = 7.4 * eV; |
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70 | highEnergyLimit = 10 * MeV; |
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71 | } |
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72 | |
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73 | |
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74 | G4FinalStateElasticScreenedRutherford::~G4FinalStateElasticScreenedRutherford() |
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75 | { |
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76 | // empty |
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77 | // G4DynamicParticle objects produced are owned by client |
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78 | } |
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79 | |
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80 | |
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81 | const G4FinalStateProduct& G4FinalStateElasticScreenedRutherford::GenerateFinalState(const G4Track& track, const G4Step& step) |
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82 | { |
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83 | // Clear previous secondaries, energy deposit and particle kill status |
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84 | product.Clear(); |
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85 | |
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86 | // Kinetic energy of primary particle |
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87 | G4double k = track.GetDynamicParticle()->GetKineticEnergy(); |
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88 | |
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89 | // Assume material = water; H2O number of electrons |
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90 | // ---- MGP ---- To be generalized later |
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91 | const G4int z = 10; |
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92 | |
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93 | G4double cosTheta = RandomizeCosTheta(k, z); |
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94 | |
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95 | G4double phi = 2. * pi * G4UniformRand(); |
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96 | |
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97 | // G4cout << "cosTheta in GenerateFinalState = " << cosTheta << ", phi = " << phi << G4endl; |
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98 | |
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99 | G4ThreeVector zVers = track.GetDynamicParticle()->GetMomentumDirection(); |
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100 | G4ThreeVector xVers = zVers.orthogonal(); |
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101 | G4ThreeVector yVers = zVers.cross(xVers); |
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102 | |
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103 | G4double xDir = std::sqrt(1. - cosTheta*cosTheta); |
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104 | G4double yDir = xDir; |
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105 | xDir *= std::cos(phi); |
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106 | yDir *= std::sin(phi); |
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107 | |
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108 | // G4cout << "xDir, yDir = " << xDir <<", " << yDir << G4endl; |
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109 | |
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110 | // G4ThreeVector zPrimeVers((xDir*xVers + yDir*yVers + cosTheta*zVers).unit()); |
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111 | G4ThreeVector zPrimeVers((xDir*xVers + yDir*yVers + cosTheta*zVers)); |
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112 | |
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113 | // G4cout << "zPrimeVers = (" << zPrimeVers.x() << ", "<< zPrimeVers.y() << ", "<< zPrimeVers.z() << ") " << G4endl; |
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114 | |
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115 | // product.ModifyPrimaryParticle(zPrimeVers.x(),zPrimeVers.y(),zPrimeVers.z(),k); |
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116 | product.ModifyPrimaryParticle(zPrimeVers,k); |
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117 | |
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118 | // this->aParticleChange.ProposeEnergy(k); |
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119 | // this->aParticleChange.ProposeMomentumDirection(zPrimeVers); |
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120 | // this->aParticleChange.SetNumberOfSecondaries(0); |
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121 | |
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122 | return product; |
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123 | } |
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124 | |
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125 | G4double G4FinalStateElasticScreenedRutherford::RandomizeCosTheta(G4double k, G4int z) const |
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126 | { |
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127 | |
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128 | // d sigma_el sigma_Ruth(K) |
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129 | // ------------ (K) ~ ----------------------------- |
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130 | // d Omega (1 + 2 n(K) - cos(theta))^2 |
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131 | // |
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132 | // We extract cos(theta) distributed as (1 + 2 n(K) - cos(theta))^-2 |
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133 | // |
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134 | // Maximum is for theta=0: 1/(4 n(K)^2) (When n(K) is positive, that is always satisfied within the validity of the process) |
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135 | // |
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136 | // Phys. Med. Biol. 45 (2000) 3171-3194 |
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137 | |
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138 | G4double n = ScreeningFactor(k, z); |
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139 | |
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140 | G4double oneOverMax = (4. * n*n); |
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141 | |
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142 | G4double cosTheta; |
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143 | G4double fCosTheta; |
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144 | |
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145 | do |
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146 | { |
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147 | cosTheta = 2. * G4UniformRand() - 1.; |
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148 | fCosTheta = (1 + 2.*n - cosTheta); |
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149 | fCosTheta = oneOverMax / (fCosTheta*fCosTheta); |
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150 | } |
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151 | while (fCosTheta < G4UniformRand()); |
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152 | |
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153 | return cosTheta; |
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154 | } |
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155 | |
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156 | G4double G4FinalStateElasticScreenedRutherford::ScreeningFactor(G4double k, G4int z) const |
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157 | { |
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158 | // |
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159 | // alpha_1 + beta_1 ln(K/eV) constK Z^(2/3) |
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160 | // n(T) = -------------------------- ----------------- |
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161 | // K/(m_e c^2) 2 + K/(m_e c^2) |
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162 | // |
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163 | // Where K is the electron non-relativistic kinetic energy |
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164 | // |
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165 | // n(T) > 0 for T < ~ 400 MeV |
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166 | // |
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167 | // Nucl. Instr. Meth. 155 (1978) 145-156 |
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168 | |
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169 | const G4double alpha_1 = 1.64; |
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170 | const G4double beta_1 = -0.0825; |
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171 | const G4double constK = 1.7E-5; |
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172 | |
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173 | G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(static_cast<double>(z), 2./3.); |
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174 | |
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175 | k /= electron_mass_c2; |
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176 | |
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177 | G4double denominator; |
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178 | denominator = k * (2 + k); |
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179 | |
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180 | G4double result = 0.; |
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181 | if (denominator != 0.) |
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182 | { |
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183 | result = numerator / denominator; |
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184 | } |
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185 | else |
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186 | { |
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187 | // Throw an exception |
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188 | G4Exception("G4FinalStateElasticScreenedRutherford::ScreeningFactor - denominator = 0"); |
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189 | } |
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190 | return result; |
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191 | |
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192 | } |
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