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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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13 | // * work make any representation or warranty, express or implied, * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4eeTo3PiModel.cc,v 1.2 2009/02/20 16:38:33 vnivanch Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-03-beta-cand-01 $ |
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28 | // |
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29 | // ------------------------------------------------------------------- |
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30 | // |
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31 | // GEANT4 Class header file |
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32 | // |
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33 | // |
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34 | // File name: G4eeTo3PiModel |
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35 | // |
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36 | // Author: Vladimir Ivanchenko |
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37 | // |
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38 | // Creation date: 25.10.2003 |
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39 | // |
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40 | // Modifications: |
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41 | // |
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42 | // |
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43 | // ------------------------------------------------------------------- |
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44 | // |
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45 | |
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46 | |
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47 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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48 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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49 | |
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50 | #include "G4eeTo3PiModel.hh" |
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51 | #include "Randomize.hh" |
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52 | #include "G4PionPlus.hh" |
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53 | #include "G4PionMinus.hh" |
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54 | #include "G4PionZero.hh" |
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55 | #include "G4DynamicParticle.hh" |
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56 | #include "G4PhysicsVector.hh" |
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57 | #include "G4PhysicsLinearVector.hh" |
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58 | #include "G4eeCrossSections.hh" |
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59 | #include "G4RandomDirection.hh" |
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60 | #include <complex> |
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61 | |
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62 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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63 | |
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64 | using namespace std; |
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65 | |
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66 | G4eeTo3PiModel::G4eeTo3PiModel(G4eeCrossSections* cr): |
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67 | cross(cr) |
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68 | { |
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69 | massPi = G4PionPlus::PionPlus()->GetPDGMass(); |
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70 | massPi0 = G4PionZero::PionZero()->GetPDGMass(); |
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71 | massOm = 782.62*MeV; |
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72 | massPhi = 1019.46*MeV; |
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73 | gcash = 0.0; |
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74 | gmax = 1.0; |
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75 | } |
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76 | |
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77 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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78 | |
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79 | G4eeTo3PiModel::~G4eeTo3PiModel() |
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80 | { |
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81 | G4cout << "### G4eeTo3PiModel::~G4eeTo3PiModel: gmax= " |
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82 | << gmax << " gcash= " << gcash << G4endl; |
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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 | G4double G4eeTo3PiModel::ThresholdEnergy() const |
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88 | { |
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89 | return std::max(LowEnergy(),2.0*massPi + massPi0); |
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90 | } |
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91 | |
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92 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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93 | |
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94 | G4double G4eeTo3PiModel::PeakEnergy() const |
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95 | { |
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96 | G4double e = massOm; |
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97 | if(HighEnergy() > massPhi) e = massPhi; |
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98 | return e; |
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99 | } |
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100 | |
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101 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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102 | |
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103 | G4double G4eeTo3PiModel::ComputeCrossSection(G4double e) const |
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104 | { |
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105 | G4double ee = std::min(HighEnergy(),e); |
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106 | return cross->CrossSection3pi(ee); |
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107 | } |
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108 | |
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109 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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110 | |
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111 | G4PhysicsVector* G4eeTo3PiModel::PhysicsVector(G4double emin, |
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112 | G4double emax) const |
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113 | { |
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114 | G4double tmin = std::max(emin, ThresholdEnergy()); |
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115 | G4double tmax = std::max(tmin, emax); |
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116 | G4int nbins = (G4int)((tmax - tmin)/(1.*MeV)); |
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117 | G4PhysicsVector* v = new G4PhysicsLinearVector(emin,emax,nbins); |
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118 | v->SetSpline(true); |
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119 | return v; |
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120 | } |
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121 | |
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122 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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123 | |
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124 | void G4eeTo3PiModel::SampleSecondaries(std::vector<G4DynamicParticle*>* newp, |
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125 | G4double e, const G4ThreeVector& direction) |
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126 | { |
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127 | if(e < ThresholdEnergy()) return; |
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128 | |
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129 | G4double x0 = massPi0/e; |
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130 | G4double x1 = massPi/e; |
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131 | |
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132 | G4LorentzVector w0, w1, w2; |
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133 | G4ThreeVector dir0, dir1, mom, mom1, mom2; |
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134 | G4double e0, p0, e2, p, g, m01, m02, m12; |
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135 | |
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136 | // max pi0 energy |
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137 | G4double edel = 0.5*e*(1.0 + x0*x0 - 4.0*x1*x1) - massPi0; |
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138 | |
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139 | do { |
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140 | // pi0 sample |
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141 | e0 = edel*G4UniformRand() + massPi0; |
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142 | p0 = sqrt(e0 - massPi0*massPi0); |
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143 | dir0 = G4RandomDirection(); |
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144 | w0 = G4LorentzVector(p0*dir0.x(),p0*dir0.y(),p0*dir0.z(),e0); |
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145 | |
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146 | // pi+pi- pair |
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147 | w1 = G4LorentzVector(-p0*dir0.x(),-p0*dir0.y(),-p0*dir0.z(),e-e0); |
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148 | G4ThreeVector bst = w1.boostVector(); |
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149 | e2 = 0.25*w1.m2(); |
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150 | |
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151 | // pi+ |
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152 | p = sqrt(e2 - massPi*massPi); |
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153 | dir1 = G4RandomDirection(); |
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154 | w2 = G4LorentzVector(p*dir1.x(),p*dir1.y(),p*dir1.z(),sqrt(e2)); |
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155 | w2.boost(bst); |
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156 | mom2 = w2.vect(); |
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157 | |
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158 | // pi- |
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159 | w1 -= w2; |
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160 | mom1 = w2.vect(); |
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161 | |
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162 | m01 = w0*w1; |
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163 | m02 = w0*w2; |
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164 | m12 = w1*w2; |
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165 | |
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166 | mom = mom1*mom2; |
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167 | g = mom.mag2()*norm( 1.0/cross->DpRho(m01) + 1.0/cross->DpRho(m02) |
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168 | + 1.0/cross->DpRho(m12) ); |
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169 | if(g > gmax) { |
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170 | G4cout << "G4eeTo3PiModel::SampleSecondaries WARNING matrix element g= " |
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171 | << g << " > " << gmax << " (majoranta)" << G4endl; |
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172 | } |
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173 | if(g > gcash) gcash = g; |
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174 | |
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175 | } while( gmax*G4UniformRand() > g ); |
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176 | |
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177 | w0.rotateUz(direction); |
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178 | w1.rotateUz(direction); |
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179 | w2.rotateUz(direction); |
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180 | |
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181 | // create G4DynamicParticle objects |
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182 | G4DynamicParticle* dp0 = |
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183 | new G4DynamicParticle(G4PionZero::PionZero(), w0); |
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184 | G4DynamicParticle* dp1 = |
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185 | new G4DynamicParticle(G4PionPlus::PionPlus(), w1); |
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186 | G4DynamicParticle* dp2 = |
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187 | new G4DynamicParticle(G4PionMinus::PionMinus(), w2); |
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188 | newp->push_back(dp0); |
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189 | newp->push_back(dp1); |
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190 | newp->push_back(dp2); |
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191 | } |
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192 | |
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193 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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194 | |
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