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25 | // |
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26 | // |
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27 | // $Id: G4SingleDiffractiveExcitation.cc,v 1.1 2007/05/25 07:30:47 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 | // ---------------- G4SingleDiffractiveExcitation -------------- |
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32 | // by Gunter Folger, October 1998. |
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33 | // diffractive Excitation used by strings models |
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34 | // Take a projectile and a target |
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35 | // excite 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 "G4SingleDiffractiveExcitation.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 "G4ios.hh" |
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49 | |
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50 | G4SingleDiffractiveExcitation::G4SingleDiffractiveExcitation(G4double sigmaPt, G4double minextraMass,G4double x0mass) |
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51 | : |
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52 | widthOfPtSquare(-2*sqr(sigmaPt)) , minExtraMass(minextraMass), |
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53 | minmass(x0mass) |
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54 | { |
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55 | } |
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56 | |
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57 | G4bool G4SingleDiffractiveExcitation:: |
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58 | ExciteParticipants(G4VSplitableHadron *projectile, G4VSplitableHadron *target) const |
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59 | { |
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60 | |
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61 | G4LorentzVector Pprojectile=projectile->Get4Momentum(); |
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62 | G4double Mprojectile2=sqr(projectile->GetDefinition()->GetPDGMass() + minExtraMass); |
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63 | |
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64 | G4LorentzVector Ptarget=target->Get4Momentum(); |
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65 | G4double Mtarget2=sqr(target->GetDefinition()->GetPDGMass() + minExtraMass); |
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66 | // G4cout << "E proj, target :" << Pprojectile.e() << ", " << |
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67 | // Ptarget.e() << G4endl; |
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68 | |
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69 | G4bool KeepProjectile= G4UniformRand() > 0.5; |
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70 | |
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71 | // reset the min.mass of the non diffractive particle to its value, ( minus a bit for rounding...) |
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72 | if ( KeepProjectile ) |
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73 | { |
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74 | // cout << " Projectile fix" << G4endl; |
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75 | Mprojectile2 = sqr(projectile->GetDefinition()->GetPDGMass() * (1-perCent) ); |
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76 | } else { |
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77 | // cout << " Target fix" << G4endl; |
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78 | Mtarget2=sqr(target->GetDefinition()->GetPDGMass() * (1-perCent) ); |
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79 | } |
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80 | |
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81 | // Transform momenta to cms and then rotate parallel to z axis; |
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82 | |
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83 | G4LorentzVector Psum; |
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84 | Psum=Pprojectile+Ptarget; |
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85 | |
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86 | G4LorentzRotation toCms(-1*Psum.boostVector()); |
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87 | |
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88 | G4LorentzVector Ptmp=toCms*Pprojectile; |
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89 | |
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90 | if ( Ptmp.pz() <= 0. ) |
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91 | { |
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92 | // "String" moving backwards in CMS, abort collision !! |
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93 | // G4cout << " abort Collision!! " << G4endl; |
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94 | return false; |
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95 | } |
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96 | |
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97 | toCms.rotateZ(-1*Ptmp.phi()); |
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98 | toCms.rotateY(-1*Ptmp.theta()); |
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99 | |
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100 | // G4cout << "Pprojectile be4 boost " << Pprojectile << G4endl; |
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101 | // G4cout << "Ptarget be4 boost : " << Ptarget << G4endl; |
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102 | |
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103 | |
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104 | |
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105 | G4LorentzRotation toLab(toCms.inverse()); |
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106 | |
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107 | Pprojectile.transform(toCms); |
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108 | Ptarget.transform(toCms); |
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109 | |
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110 | G4LorentzVector Qmomentum; |
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111 | G4int whilecount=0; |
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112 | do { |
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113 | // Generate pt |
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114 | |
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115 | G4double maxPtSquare=sqr(Ptarget.pz()); |
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116 | if (whilecount++ >= 500 && (whilecount%100)==0) |
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117 | // G4cout << "G4SingleDiffractiveExcitation::ExciteParticipants possibly looping" |
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118 | // << ", loop count/ maxPtSquare : " |
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119 | // << whilecount << " / " << maxPtSquare << G4endl; |
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120 | if (whilecount > 1000 ) |
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121 | { |
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122 | Qmomentum=G4LorentzVector(0.,0.,0.,0.); |
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123 | // G4cout << "G4SingleDiffractiveExcitation::ExciteParticipants: Aborting loop!" << G4endl; |
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124 | return false; // Ignore this interaction |
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125 | } |
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126 | Qmomentum=G4LorentzVector(GaussianPt(widthOfPtSquare,maxPtSquare),0); |
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127 | |
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128 | |
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129 | // Momentum transfer |
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130 | G4double Xmin = minmass / ( Pprojectile.e() + Ptarget.e() ); |
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131 | G4double Xmax=1.; |
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132 | G4double Xplus =ChooseX(Xmin,Xmax); |
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133 | G4double Xminus=ChooseX(Xmin,Xmax); |
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134 | |
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135 | G4double pt2=G4ThreeVector(Qmomentum.vect()).mag2(); |
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136 | G4double Qplus =-1 * pt2 / Xminus/Ptarget.minus(); |
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137 | G4double Qminus= pt2 / Xplus /Pprojectile.plus(); |
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138 | |
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139 | if ( KeepProjectile ) |
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140 | { |
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141 | Qminus = (sqr(projectile->GetDefinition()->GetPDGMass()) + pt2 ) |
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142 | / (Pprojectile.plus() + Qplus ) |
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143 | - Pprojectile.minus(); |
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144 | } else |
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145 | { |
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146 | Qplus = Ptarget.plus() |
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147 | - (sqr(target->GetDefinition()->GetPDGMass()) + pt2 ) |
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148 | / (Ptarget.minus() - Qminus ); |
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149 | } |
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150 | |
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151 | Qmomentum.setPz( (Qplus-Qminus)/2 ); |
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152 | Qmomentum.setE( (Qplus+Qminus)/2 ); |
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153 | |
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154 | // G4cout << "Qplus / Qminus " << Qplus << " / " << Qminus<<G4endl; |
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155 | // G4cout << "pt2 " << pt2 << G4endl; |
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156 | // G4cout << "Qmomentum " << Qmomentum << G4endl; |
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157 | // G4cout << " Masses (P/T) : " << (Pprojectile+Qmomentum).mag() << |
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158 | // " / " << (Ptarget-Qmomentum).mag() << G4endl; |
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159 | |
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160 | } while ( (Ptarget-Qmomentum).mag2() <= Mtarget2 |
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161 | || (Pprojectile+Qmomentum).mag2() <= Mprojectile2 |
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162 | || (Ptarget-Qmomentum).e() < 0. |
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163 | || (Pprojectile+Qmomentum).e() < 0. ); |
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164 | |
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165 | |
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166 | // G4double Ecms=Pprojectile.e() + Ptarget.e(); |
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167 | |
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168 | Pprojectile += Qmomentum; |
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169 | |
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170 | Ptarget -= Qmomentum; |
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171 | |
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172 | // G4cout << "Pprojectile.e() : " << Pprojectile.e() << G4endl; |
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173 | // G4cout << "Ptarget.e() : " << Ptarget.e() << G4endl; |
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174 | |
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175 | // G4cout << "end event_______________________________________________"<<G4endl; |
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176 | // |
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177 | |
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178 | |
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179 | // G4cout << "Pprojectile with Q : " << Pprojectile << G4endl; |
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180 | // G4cout << "Ptarget with Q : " << Ptarget << G4endl; |
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181 | // G4cout << "Projectile back: " << toLab * Pprojectile << G4endl; |
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182 | // G4cout << "Target back: " << toLab * Ptarget << G4endl; |
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183 | |
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184 | // Transform back and update SplitableHadron Participant. |
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185 | Pprojectile.transform(toLab); |
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186 | Ptarget.transform(toLab); |
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187 | |
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188 | // G4cout << "G4SingleDiffractiveExcitation- Target mass " << Ptarget.mag() << G4endl; |
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189 | // G4cout << "G4SingleDiffractiveExcitation- Projectile mass " << Pprojectile.mag() << G4endl; |
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190 | |
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191 | target->Set4Momentum(Ptarget); |
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192 | projectile->Set4Momentum(Pprojectile); |
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193 | |
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194 | |
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195 | return true; |
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196 | } |
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197 | |
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198 | |
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199 | |
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200 | |
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201 | // --------- private methods ---------------------- |
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202 | |
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203 | G4double G4SingleDiffractiveExcitation::ChooseX(G4double Xmin, G4double Xmax) const |
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204 | { |
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205 | // choose an x between Xmin and Xmax with P(x) ~ 1/x |
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206 | |
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207 | // to be improved... |
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208 | |
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209 | G4double range=Xmax-Xmin; |
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210 | |
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211 | if ( Xmin <= 0. || range <=0. ) |
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212 | { |
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213 | G4cout << " Xmin, range : " << Xmin << " , " << range << G4endl; |
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214 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation::ChooseX : Invalid arguments "); |
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215 | } |
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216 | |
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217 | G4double x; |
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218 | do { |
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219 | x=Xmin + G4UniformRand() * range; |
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220 | } while ( Xmin/x < G4UniformRand() ); |
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221 | |
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222 | // cout << "DiffractiveX "<<x<<G4endl; |
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223 | return x; |
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224 | } |
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225 | |
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226 | G4ThreeVector G4SingleDiffractiveExcitation::GaussianPt(G4double widthSquare, G4double maxPtSquare) const |
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227 | { // @@ this method is used in FTFModel as well. Should go somewhere common! |
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228 | |
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229 | G4double pt2; |
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230 | |
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231 | do { |
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232 | pt2=widthSquare * std::log( G4UniformRand() ); |
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233 | } while ( pt2 > maxPtSquare); |
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234 | |
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235 | pt2=std::sqrt(pt2); |
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236 | |
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237 | G4double phi=G4UniformRand() * twopi; |
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238 | |
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239 | return G4ThreeVector (pt2*std::cos(phi), pt2*std::sin(phi), 0.); |
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240 | } |
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241 | |
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242 | G4SingleDiffractiveExcitation::G4SingleDiffractiveExcitation(const G4SingleDiffractiveExcitation &) |
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243 | : G4QGSDiffractiveExcitation(), |
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244 | widthOfPtSquare(0) , minExtraMass(0), |
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245 | minmass(0) |
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246 | { |
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247 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation copy contructor not meant to be called"); |
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248 | } |
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249 | |
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250 | |
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251 | G4SingleDiffractiveExcitation::~G4SingleDiffractiveExcitation() |
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252 | { |
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253 | } |
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254 | |
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255 | |
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256 | const G4SingleDiffractiveExcitation & G4SingleDiffractiveExcitation::operator=(const G4SingleDiffractiveExcitation &) |
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257 | { |
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258 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation = operator meant to be called"); |
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259 | return *this; |
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260 | } |
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261 | |
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262 | |
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263 | int G4SingleDiffractiveExcitation::operator==(const G4SingleDiffractiveExcitation &) const |
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264 | { |
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265 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation == operator meant to be called"); |
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266 | return false; |
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267 | } |
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268 | |
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269 | int G4SingleDiffractiveExcitation::operator!=(const G4SingleDiffractiveExcitation &) const |
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270 | { |
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271 | throw G4HadronicException(__FILE__, __LINE__, "G4SingleDiffractiveExcitation != operator meant to be called"); |
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272 | return true; |
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273 | } |
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274 | |
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275 | |
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276 | |
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277 | |
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278 | |
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