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2 | // ******************************************************************** |
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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 | // |
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27 | // $Id: G4ElasticHNScattering.cc,v 1.14 2009/12/16 17:51:13 gunter Exp $ |
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28 | // ------------------------------------------------------------ |
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29 | // GEANT 4 class implemetation file |
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30 | // |
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31 | // ---------------- G4ElasticHNScattering -------------- |
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32 | // by V. Uzhinsky, March 2008. |
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33 | // elastic scattering used by Fritiof model |
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34 | // Take a projectile and a target |
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35 | // scatter the projectile and target |
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36 | // --------------------------------------------------------------------- |
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37 | |
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38 | |
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39 | #include "globals.hh" |
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40 | #include "Randomize.hh" |
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41 | |
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42 | #include "G4ElasticHNScattering.hh" |
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43 | #include "G4LorentzRotation.hh" |
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44 | #include "G4ThreeVector.hh" |
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45 | #include "G4ParticleDefinition.hh" |
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46 | #include "G4VSplitableHadron.hh" |
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47 | #include "G4ExcitedString.hh" |
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48 | #include "G4FTFParameters.hh" |
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49 | //#include "G4ios.hh" |
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50 | |
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51 | G4ElasticHNScattering::G4ElasticHNScattering() |
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52 | { |
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53 | } |
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54 | |
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55 | G4bool G4ElasticHNScattering:: |
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56 | ElasticScattering (G4VSplitableHadron *projectile, |
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57 | G4VSplitableHadron *target, |
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58 | G4FTFParameters *theParameters) const |
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59 | { |
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60 | // -------------------- Projectile parameters ----------------------------------- |
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61 | G4LorentzVector Pprojectile=projectile->Get4Momentum(); |
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62 | |
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63 | if(Pprojectile.z() < 0.) |
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64 | { |
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65 | target->SetStatus(2); |
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66 | return false; |
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67 | } |
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68 | |
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69 | G4bool PutOnMassShell(false); |
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70 | |
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71 | G4double M0projectile = Pprojectile.mag(); |
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72 | if(M0projectile < projectile->GetDefinition()->GetPDGMass()) |
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73 | { |
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74 | PutOnMassShell=true; |
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75 | M0projectile=projectile->GetDefinition()->GetPDGMass(); |
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76 | } |
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77 | |
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78 | G4double Mprojectile2 = M0projectile * M0projectile; |
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79 | |
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80 | G4double AveragePt2=theParameters->GetAvaragePt2ofElasticScattering(); |
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81 | |
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82 | // -------------------- Target parameters ---------------------------------------------- |
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83 | |
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84 | G4LorentzVector Ptarget=target->Get4Momentum(); |
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85 | |
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86 | G4double M0target = Ptarget.mag(); |
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87 | |
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88 | if(M0target < target->GetDefinition()->GetPDGMass()) |
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89 | { |
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90 | PutOnMassShell=true; |
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91 | M0target=target->GetDefinition()->GetPDGMass(); |
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92 | } |
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93 | |
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94 | G4double Mtarget2 = M0target * M0target; |
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95 | |
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96 | // Transform momenta to cms and then rotate parallel to z axis; |
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97 | |
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98 | G4LorentzVector Psum; |
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99 | Psum=Pprojectile+Ptarget; |
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100 | |
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101 | G4LorentzRotation toCms(-1*Psum.boostVector()); |
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102 | |
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103 | G4LorentzVector Ptmp=toCms*Pprojectile; |
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104 | |
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105 | if ( Ptmp.pz() <= 0. ) |
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106 | { |
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107 | // "String" moving backwards in CMS, abort collision !! |
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108 | //G4cout << " abort Collision!! " << G4endl; |
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109 | target->SetStatus(2); |
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110 | return false; |
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111 | } |
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112 | |
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113 | toCms.rotateZ(-1*Ptmp.phi()); |
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114 | toCms.rotateY(-1*Ptmp.theta()); |
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115 | |
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116 | G4LorentzRotation toLab(toCms.inverse()); |
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117 | |
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118 | Pprojectile.transform(toCms); |
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119 | Ptarget.transform(toCms); |
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120 | |
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121 | // ---------------------- Putting on mass-on-shell, if needed ------------------------ |
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122 | G4double PZcms2, PZcms; |
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123 | |
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124 | G4double S=Psum.mag2(); |
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125 | // G4double SqrtS=std::sqrt(S); |
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126 | |
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127 | PZcms2=(S*S+Mprojectile2*Mprojectile2+Mtarget2*Mtarget2- |
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128 | 2*S*Mprojectile2-2*S*Mtarget2-2*Mprojectile2*Mtarget2)/4./S; |
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129 | |
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130 | if(PZcms2 < 0.) |
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131 | { // It can be in an interaction with off-shell nuclear nucleon |
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132 | if(M0projectile > projectile->GetDefinition()->GetPDGMass()) |
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133 | { // An attempt to de-excite the projectile |
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134 | // It is assumed that the target is in the ground state |
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135 | M0projectile = projectile->GetDefinition()->GetPDGMass(); |
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136 | Mprojectile2=M0projectile*M0projectile; |
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137 | PZcms2=(S*S+Mprojectile2*Mprojectile2+Mtarget2*Mtarget2- |
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138 | 2*S*Mprojectile2 - 2*S*Mtarget2 - 2*Mprojectile2*Mtarget2) |
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139 | /4./S; |
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140 | if(PZcms2 < 0.){ return false;} // Non succesful attempt after the de-excitation |
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141 | } |
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142 | else // if(M0projectile > projectile->GetDefinition()->GetPDGMass()) |
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143 | { |
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144 | target->SetStatus(2); |
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145 | return false; // The projectile was not excited, |
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146 | // but the energy was too low to put |
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147 | // the target nucleon on mass-shell |
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148 | } // end of if(M0projectile > projectile->GetDefinition()->GetPDGMass()) |
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149 | } // end of if(PZcms2 < 0.) |
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150 | |
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151 | PZcms = std::sqrt(PZcms2); |
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152 | |
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153 | if(PutOnMassShell) |
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154 | { |
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155 | if(Pprojectile.z() > 0.) |
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156 | { |
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157 | Pprojectile.setPz( PZcms); |
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158 | Ptarget.setPz( -PZcms); |
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159 | } |
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160 | else // if(Pprojectile.z() > 0.) |
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161 | { |
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162 | Pprojectile.setPz(-PZcms); |
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163 | Ptarget.setPz( PZcms); |
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164 | }; |
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165 | |
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166 | Pprojectile.setE(std::sqrt(Mprojectile2+ |
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167 | Pprojectile.x()*Pprojectile.x()+ |
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168 | Pprojectile.y()*Pprojectile.y()+ |
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169 | PZcms2)); |
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170 | Ptarget.setE(std::sqrt( Mtarget2 + |
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171 | Ptarget.x()*Ptarget.x()+ |
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172 | Ptarget.y()*Ptarget.y()+ |
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173 | PZcms2)); |
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174 | } // end of if(PutOnMassShell) |
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175 | |
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176 | G4double maxPtSquare = PZcms2; |
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177 | |
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178 | // ------ Now we can calculate the transfered Pt -------------------------- |
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179 | G4double Pt2; |
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180 | G4double ProjMassT2, ProjMassT; |
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181 | G4double TargMassT2, TargMassT; |
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182 | |
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183 | G4LorentzVector Qmomentum; |
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184 | |
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185 | Qmomentum=G4LorentzVector(GaussianPt(AveragePt2,maxPtSquare),0); |
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186 | |
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187 | Pt2=G4ThreeVector(Qmomentum.vect()).mag2(); |
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188 | |
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189 | ProjMassT2=Mprojectile2+Pt2; |
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190 | ProjMassT =std::sqrt(ProjMassT2); |
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191 | |
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192 | TargMassT2=Mtarget2+Pt2; |
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193 | TargMassT =std::sqrt(TargMassT2); |
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194 | |
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195 | PZcms2=(S*S+ProjMassT2*ProjMassT2+ |
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196 | TargMassT2*TargMassT2- |
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197 | 2.*S*ProjMassT2-2.*S*TargMassT2- |
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198 | 2.*ProjMassT2*TargMassT2)/4./S; |
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199 | if(PZcms2 < 0 ) {PZcms2=0;};// to avoid the exactness problem |
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200 | PZcms =std::sqrt(PZcms2); |
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201 | |
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202 | Pprojectile.setPz( PZcms); |
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203 | Ptarget.setPz( -PZcms); |
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204 | |
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205 | Pprojectile += Qmomentum; |
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206 | Ptarget -= Qmomentum; |
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207 | |
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208 | // Transform back and update SplitableHadron Participant. |
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209 | Pprojectile.transform(toLab); |
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210 | Ptarget.transform(toLab); |
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211 | /* // Maybe it will be needed for an exact calculations-------------------- |
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212 | G4double TargetMomentum=std::sqrt(Ptarget.x()*Ptarget.x()+ |
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213 | Ptarget.y()*Ptarget.y()+ |
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214 | Ptarget.z()*Ptarget.z()); |
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215 | */ |
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216 | |
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217 | // Calculation of the creation time --------------------- |
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218 | projectile->SetTimeOfCreation(target->GetTimeOfCreation()); |
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219 | projectile->SetPosition(target->GetPosition()); |
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220 | // Creation time and position of target nucleon were determined at |
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221 | // ReggeonCascade() of G4FTFModel |
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222 | // ------------------------------------------------------ |
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223 | |
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224 | projectile->Set4Momentum(Pprojectile); |
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225 | target->Set4Momentum(Ptarget); |
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226 | |
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227 | projectile->IncrementCollisionCount(1); |
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228 | target->IncrementCollisionCount(1); |
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229 | |
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230 | return true; |
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231 | } |
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232 | |
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233 | |
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234 | // --------- private methods ---------------------- |
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235 | |
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236 | G4ThreeVector G4ElasticHNScattering::GaussianPt(G4double AveragePt2, G4double maxPtSquare) const |
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237 | { // @@ this method is used in FTFModel as well. Should go somewhere common! |
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238 | |
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239 | G4double Pt2(0.); |
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240 | if(AveragePt2 <= 0.) {Pt2=0.;} |
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241 | else |
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242 | { |
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243 | Pt2 = -AveragePt2 * std::log(1. + G4UniformRand() * |
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244 | (std::exp(-maxPtSquare/AveragePt2)-1.)); |
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245 | } |
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246 | G4double Pt=std::sqrt(Pt2); |
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247 | G4double phi=G4UniformRand() * twopi; |
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248 | |
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249 | return G4ThreeVector (Pt*std::cos(phi), Pt*std::sin(phi), 0.); |
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250 | } |
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251 | |
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252 | G4ElasticHNScattering::G4ElasticHNScattering(const G4ElasticHNScattering &) |
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253 | { |
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254 | throw G4HadronicException(__FILE__, __LINE__, "G4ElasticHNScattering copy contructor not meant to be called"); |
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255 | } |
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256 | |
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257 | |
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258 | G4ElasticHNScattering::~G4ElasticHNScattering() |
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259 | { |
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260 | } |
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261 | |
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262 | |
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263 | const G4ElasticHNScattering & G4ElasticHNScattering::operator=(const G4ElasticHNScattering &) |
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264 | { |
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265 | throw G4HadronicException(__FILE__, __LINE__, "G4ElasticHNScattering = operator meant to be called"); |
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266 | return *this; |
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267 | } |
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268 | |
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269 | |
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270 | int G4ElasticHNScattering::operator==(const G4ElasticHNScattering &) const |
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271 | { |
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272 | throw G4HadronicException(__FILE__, __LINE__, "G4ElasticHNScattering == operator meant to be called"); |
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273 | return false; |
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274 | } |
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275 | |
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276 | int G4ElasticHNScattering::operator!=(const G4ElasticHNScattering &) const |
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277 | { |
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278 | throw G4HadronicException(__FILE__, __LINE__, "G4ElasticHNScattering != operator meant to be called"); |
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279 | return true; |
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280 | } |
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