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15 | // * use. Please see the license in the file LICENSE and URL above * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // G4IonCoulombCrossSection.cc |
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27 | //------------------------------------------------------------------- |
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28 | // |
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29 | // GEANT4 Class header file |
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30 | // |
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31 | // File name: G4IonCoulombCrossSection |
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32 | // |
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33 | // Author: Cristina Consolandi |
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34 | // |
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35 | // Creation date: 05.10.2010 from G4eCoulombScatteringModel |
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36 | // |
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37 | // Class Description: |
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38 | // Computation of Screen-Coulomb Cross Section |
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39 | // for protons, alpha and heavy Ions |
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40 | // |
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41 | // |
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42 | // Reference: |
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43 | // M.J. Boschini et al. "Nuclear and Non-Ionizing Energy-Loss |
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44 | // for Coulomb Scattered Particles from Low Energy up to Relativistic |
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45 | // Regime in Space Radiation Environment" |
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46 | // Accepted for publication in the Proceedings of the ICATPP Conference |
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47 | // on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo, 7-8 |
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48 | // October, 2010, to be published by World Scientific (Singapore). |
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49 | // |
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50 | // Available for downloading at: |
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51 | // http://arxiv.org/abs/1011.4822 |
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52 | // |
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53 | // ------------------------------------------------------------------- |
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54 | // |
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55 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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56 | #include "G4IonCoulombCrossSection.hh" |
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57 | #include "Randomize.hh" |
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58 | #include "G4Proton.hh" |
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59 | #include "G4LossTableManager.hh" |
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60 | |
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61 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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62 | |
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63 | |
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64 | using namespace std; |
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65 | |
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66 | G4IonCoulombCrossSection::G4IonCoulombCrossSection(): |
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67 | cosThetaMin(1.0), |
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68 | cosThetaMax(-1.0), |
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69 | alpha2(fine_structure_const*fine_structure_const) |
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70 | { |
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71 | fNistManager = G4NistManager::Instance(); |
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72 | theProton = G4Proton::Proton(); |
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73 | particle=0; |
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74 | |
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75 | G4double p0 = electron_mass_c2*classic_electr_radius; |
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76 | coeff = twopi*p0*p0; |
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77 | |
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78 | cosTetMinNuc=0; |
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79 | cosTetMaxNuc=0; |
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80 | nucXSection =0; |
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81 | |
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82 | |
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83 | chargeSquare = spin = mass =0; |
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84 | tkinLab = momLab2 = invbetaLab2=0; |
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85 | tkin = mom2 = invbeta2=0; |
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86 | |
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87 | targetZ = targetMass = screenZ =0; |
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88 | ScreenRSquare=0.; |
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89 | |
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90 | etag = ecut = 0.0; |
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91 | |
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92 | } |
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93 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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94 | |
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95 | G4IonCoulombCrossSection::~G4IonCoulombCrossSection() |
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96 | {} |
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97 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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98 | |
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99 | void G4IonCoulombCrossSection::Initialise(const G4ParticleDefinition* p, |
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100 | G4double CosThetaLim) |
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101 | { |
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102 | |
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103 | SetupParticle(p); |
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104 | nucXSection = 0.0; |
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105 | tkin = targetZ = mom2 = DBL_MIN; |
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106 | ecut = etag = DBL_MAX; |
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107 | particle = p; |
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108 | |
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109 | |
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110 | cosThetaMin = CosThetaLim; |
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111 | |
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112 | } |
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113 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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114 | |
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115 | void G4IonCoulombCrossSection::SetupKinematic(G4double ekin, |
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116 | G4double cut,G4int iz ) |
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117 | { |
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118 | if(ekin != tkinLab || ecut != cut) { |
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119 | |
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120 | // lab |
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121 | tkinLab = ekin; |
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122 | momLab2 = tkinLab*(tkinLab + 2.0*mass); |
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123 | invbetaLab2 = 1.0 + mass*mass/momLab2; |
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124 | |
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125 | G4double etot = tkinLab + mass; |
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126 | G4double ptot = sqrt(momLab2); |
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127 | G4double m12 = mass*mass; |
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128 | |
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129 | targetMass=fNistManager->GetAtomicMassAmu(iz)*amu_c2; |
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130 | G4double m2 = targetMass; |
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131 | |
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132 | // relativistic reduced mass from publucation |
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133 | // A.P. Martynenko, R.N. Faustov, Teoret. mat. Fiz. 64 (1985) 179 |
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134 | |
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135 | //incident particle & target nucleus |
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136 | G4double Ecm=sqrt(m12 + m2*m2 + 2.0*etot*m2); |
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137 | G4double mu_rel=mass*m2/Ecm; |
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138 | G4double momCM= ptot*m2/Ecm; |
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139 | // relative system |
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140 | mom2 = momCM*momCM; |
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141 | invbeta2 = 1.0 + mu_rel*mu_rel/mom2; |
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142 | tkin = momCM*sqrt(invbeta2) - mu_rel;//Ekin of mu_rel |
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143 | //......................................................... |
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144 | |
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145 | cosTetMinNuc = cosThetaMin; |
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146 | cosTetMaxNuc = cosThetaMax; |
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147 | |
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148 | } |
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149 | |
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150 | } |
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151 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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152 | |
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153 | |
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154 | void G4IonCoulombCrossSection::SetupTarget(G4double Z, G4double e, G4int heavycorr) |
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155 | { |
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156 | if(Z != targetZ || e != etag) { |
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157 | etag = e; |
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158 | targetZ = Z; |
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159 | G4int iz= G4int(Z); |
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160 | |
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161 | SetScreenRSquare(iz); |
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162 | screenZ =0; |
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163 | screenZ = ScreenRSquare/mom2; |
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164 | |
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165 | // G4cout<< "heavycorr "<<heavycorr<<G4endl; |
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166 | |
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167 | if(heavycorr!=0 && particle != theProton){ |
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168 | G4double corr=5.*twopi*Z*std::sqrt(chargeSquare*alpha2); |
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169 | corr=std::pow(corr,0.12); |
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170 | screenZ *=(1.13 + corr*3.76*Z*Z*chargeSquare*invbeta2*alpha2)/2.; |
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171 | // G4cout<<" heavycorr Z e corr....2As "<< heavycorr << "\t" |
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172 | // <<Z <<"\t"<<e/MeV <<"\t"<<screenZ<<G4endl; |
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173 | |
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174 | }else{ screenZ *=(1.13 + 3.76*Z*Z*chargeSquare*invbeta2*alpha2)/2.; |
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175 | // G4cout<<" heavycorr Z e....2As "<< heavycorr << "\t" |
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176 | // <<Z <<"\t"<< e/MeV <<"\t" <<screenZ<<G4endl; |
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177 | } |
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178 | |
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179 | if(1 == iz && particle == theProton && cosTetMaxNuc < 0.0) { |
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180 | cosTetMaxNuc = 0.0; |
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181 | } |
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182 | |
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183 | } |
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184 | } |
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185 | |
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186 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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187 | void G4IonCoulombCrossSection::SetScreenRSquare(G4int iz){ |
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188 | |
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189 | G4double a0 = electron_mass_c2/0.88534; |
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190 | |
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191 | //target nucleus |
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192 | G4double Z1=std::sqrt(chargeSquare); |
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193 | G4double Z2=targetZ; |
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194 | |
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195 | G4double Z1023=std::pow(Z1,0.23); |
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196 | G4double Z2023=std::pow(Z2,0.23); |
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197 | |
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198 | // Universal screening length |
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199 | G4double x=a0*(Z1023+Z2023); |
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200 | |
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201 | //for proton Thomas-Fermi screening length |
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202 | if(particle == theProton){ |
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203 | x = a0*fNistManager->GetZ13(iz); |
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204 | } |
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205 | ScreenRSquare = alpha2*x*x; |
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206 | |
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207 | |
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208 | } |
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209 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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210 | |
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211 | G4double G4IonCoulombCrossSection::NuclearCrossSection() |
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212 | { |
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213 | // This method needs initialisation before be called |
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214 | |
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215 | // scattering with target nucleus |
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216 | G4double fac = coeff*targetZ*targetZ*chargeSquare*invbeta2/mom2; |
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217 | |
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218 | nucXSection = 0.0; |
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219 | |
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220 | G4double x = 1.0 - cosTetMinNuc; |
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221 | G4double x1 = x + screenZ; |
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222 | |
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223 | // scattering with nucleus |
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224 | if(cosTetMaxNuc < cosTetMinNuc) { |
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225 | |
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226 | nucXSection =fac*(cosTetMinNuc - cosTetMaxNuc)/ |
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227 | (x1*(1.0 - cosTetMaxNuc + screenZ)); |
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228 | |
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229 | } |
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230 | |
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231 | return nucXSection; |
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232 | } |
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233 | |
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234 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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235 | |
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236 | G4double G4IonCoulombCrossSection::SampleCosineTheta() |
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237 | { |
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238 | |
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239 | if(cosTetMaxNuc >= cosTetMinNuc) return 0.0; |
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240 | |
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241 | G4double x1 = 1. - cosTetMinNuc + screenZ; |
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242 | G4double x2 = 1. - cosTetMaxNuc + screenZ; |
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243 | G4double dx = cosTetMinNuc - cosTetMaxNuc; |
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244 | G4double grej, z1; |
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245 | |
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246 | z1 = x1*x2/(x1 + G4UniformRand()*dx) - screenZ; |
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247 | grej = 1.0/(1.0 + z1); |
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248 | |
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249 | |
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250 | return z1; |
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251 | } |
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252 | |
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253 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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254 | |
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255 | |
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256 | |
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257 | |
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