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 | // GEANT 4 class header file |
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28 | // |
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29 | // History: |
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30 | // 17 August 2004 P. Gumplinger, T. MacPhail |
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31 | // ------------------------------------------------------------ |
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32 | // |
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33 | #include "G4DecayWithSpin.hh" |
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34 | |
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35 | #include "G4Step.hh" |
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36 | #include "G4Track.hh" |
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37 | #include "G4DecayTable.hh" |
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38 | #include "G4MuonDecayChannelWithSpin.hh" |
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39 | |
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40 | #include "G4Vector3D.hh" |
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41 | |
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42 | #include "G4TransportationManager.hh" |
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43 | #include "G4PropagatorInField.hh" |
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44 | #include "G4FieldManager.hh" |
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45 | #include "G4Field.hh" |
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46 | |
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47 | #include "G4Transform3D.hh" |
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48 | |
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49 | G4DecayWithSpin::G4DecayWithSpin(const G4String& processName):G4Decay(processName){} |
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50 | |
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51 | G4DecayWithSpin::~G4DecayWithSpin(){} |
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52 | |
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53 | G4VParticleChange* G4DecayWithSpin::DecayIt(const G4Track& aTrack, const G4Step& aStep) |
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54 | { |
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55 | |
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56 | // get particle |
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57 | const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle(); |
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58 | G4ParticleDefinition* aParticleDef = aParticle->GetDefinition(); |
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59 | |
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60 | // get parent_polarization |
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61 | G4ThreeVector parent_polarization = aParticle->GetPolarization(); |
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62 | |
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63 | if(parent_polarization == G4ThreeVector(0,0,0)) |
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64 | { |
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65 | // Generate random polarization direction |
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66 | |
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67 | G4double cost = 1. - 2.*G4UniformRand(); |
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68 | G4double sint = std::sqrt((1.-cost)*(1.+cost)); |
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69 | |
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70 | G4double phi = twopi*G4UniformRand(); |
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71 | G4double sinp = std::sin(phi); |
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72 | G4double cosp = std::cos(phi); |
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73 | |
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74 | G4double px = sint*cosp; |
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75 | G4double py = sint*sinp; |
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76 | G4double pz = cost; |
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77 | |
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78 | parent_polarization.setX(px); |
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79 | parent_polarization.setY(py); |
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80 | parent_polarization.setZ(pz); |
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81 | |
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82 | }else{ |
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83 | |
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84 | G4FieldManager* fieldMgr = aStep.GetTrack()->GetVolume()-> |
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85 | GetLogicalVolume()->GetFieldManager(); |
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86 | |
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87 | if (!fieldMgr) { |
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88 | G4TransportationManager *transportMgr = |
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89 | G4TransportationManager::GetTransportationManager(); |
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90 | G4PropagatorInField* fFieldPropagator = |
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91 | transportMgr->GetPropagatorInField(); |
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92 | if (fFieldPropagator) fieldMgr = |
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93 | fFieldPropagator->GetCurrentFieldManager(); |
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94 | } |
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95 | |
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96 | const G4Field* field = NULL; |
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97 | if(fieldMgr)field = fieldMgr->GetDetectorField(); |
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98 | |
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99 | if (field && !(fieldMgr->DoesFieldChangeEnergy())) { |
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100 | |
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101 | G4double point[4]; |
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102 | point[0] = (aStep.GetPostStepPoint()->GetPosition())[0]; |
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103 | point[1] = (aStep.GetPostStepPoint()->GetPosition())[1]; |
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104 | point[2] = (aStep.GetPostStepPoint()->GetPosition())[2]; |
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105 | point[3] = aTrack.GetGlobalTime(); |
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106 | |
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107 | G4double fieldValue[3]; |
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108 | field -> GetFieldValue(point,fieldValue); |
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109 | |
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110 | G4ThreeVector B(fieldValue[0],fieldValue[1],fieldValue[2]); |
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111 | |
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112 | parent_polarization = Spin_Precession(aStep,B,fRemainderLifeTime); |
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113 | |
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114 | } |
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115 | } |
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116 | |
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117 | // decay table |
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118 | G4DecayTable *decaytable = aParticleDef->GetDecayTable(); |
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119 | |
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120 | if (decaytable) { |
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121 | G4MuonDecayChannelWithSpin *decaychannel; |
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122 | decaychannel = (G4MuonDecayChannelWithSpin*)decaytable->SelectADecayChannel(); |
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123 | if (decaychannel) decaychannel->SetPolarization(parent_polarization); |
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124 | } |
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125 | |
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126 | G4ParticleChangeForDecay* pParticleChangeForDecay; |
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127 | |
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128 | pParticleChangeForDecay = (G4ParticleChangeForDecay*)G4Decay::DecayIt(aTrack,aStep); |
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129 | |
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130 | pParticleChangeForDecay->ProposePolarization(parent_polarization); |
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131 | |
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132 | return pParticleChangeForDecay; |
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133 | |
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134 | } |
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135 | |
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136 | G4ThreeVector G4DecayWithSpin::Spin_Precession( const G4Step& aStep, |
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137 | G4ThreeVector B, G4double deltatime ) |
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138 | { |
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139 | G4double Bnorm = std::sqrt(sqr(B[0]) + sqr(B[1]) +sqr(B[2]) ); |
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140 | |
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141 | G4double q = aStep.GetTrack()->GetDefinition()->GetPDGCharge(); |
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142 | G4double a = 1.165922e-3; |
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143 | G4double s_omega = 8.5062e+7*rad/(s*kilogauss); |
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144 | |
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145 | G4double omega = -(q*s_omega)*(1.+a) * Bnorm; |
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146 | |
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147 | G4double rotationangle = deltatime * omega; |
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148 | |
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149 | G4Transform3D SpinRotation = G4Rotate3D(rotationangle,B.unit()); |
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150 | |
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151 | G4Vector3D Spin = aStep.GetTrack() -> GetPolarization(); |
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152 | |
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153 | G4Vector3D newSpin = SpinRotation * Spin; |
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154 | |
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155 | #ifdef G4VERBOSE |
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156 | if (GetVerboseLevel()>2) { |
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157 | G4double normspin = std::sqrt(Spin*Spin); |
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158 | G4double normnewspin = std::sqrt(newSpin*newSpin); |
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159 | //G4double cosalpha = Spin*newSpin/normspin/normnewspin; |
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160 | //G4double alpha = std::acos(cosalpha); |
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161 | |
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162 | G4cout << "AT REST::: PARAMETERS " << G4endl; |
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163 | G4cout << "Initial spin : " << Spin << G4endl; |
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164 | G4cout << "Delta time : " << deltatime << G4endl; |
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165 | G4cout << "Rotation angle: " << rotationangle/rad << G4endl; |
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166 | G4cout << "New spin : " << newSpin << G4endl; |
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167 | G4cout << "Checked norms : " << normspin <<" " << normnewspin << G4endl; |
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168 | } |
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169 | #endif |
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170 | |
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171 | return newSpin; |
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172 | |
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173 | } |
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