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 | // -- Bogus -- BaBar Object-Oriented Geant-based Unified Simulation |
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28 | // |
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29 | // NTSTLooperDeath |
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30 | // |
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31 | // Description: |
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32 | // This is a simple GEANT4 process that destroys any particle below |
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33 | // the specified total kinetic energy that reverse direction (loops 180 |
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34 | // degress) in the x/y plane. |
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35 | // |
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36 | // Based on BgsChargedLowEnergyDeath |
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37 | // |
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38 | // Author List: |
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39 | // David Williams |
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40 | // |
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41 | // Modification History: |
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42 | // |
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43 | //----------------------------------------------------------------------------- |
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44 | |
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45 | #include "NTSTLooperDeath.hh" |
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46 | |
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47 | #include "G4TransportationManager.hh" |
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48 | #include "G4FieldManager.hh" |
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49 | #include "G4MagneticField.hh" |
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50 | |
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51 | // |
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52 | // Constructor |
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53 | // |
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54 | NTSTLooperDeath::NTSTLooperDeath( G4double theMinMomentum, |
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55 | const char* name, |
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56 | G4ProcessType type ) |
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57 | : G4VProcess( name, type ), minMomentum( theMinMomentum ) |
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58 | {;} |
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59 | |
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60 | NTSTLooperDeath::~NTSTLooperDeath(){;} |
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61 | // |
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62 | // PostStepGetPhysicalInteractionLength |
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63 | // |
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64 | G4double NTSTLooperDeath::PostStepGetPhysicalInteractionLength( |
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65 | const G4Track& track, |
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66 | G4double , // previousStepSize, |
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67 | G4ForceCondition* condition ) |
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68 | { |
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69 | const G4DynamicParticle *particle = track.GetDynamicParticle(); |
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70 | |
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71 | *condition = NotForced; |
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72 | |
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73 | // |
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74 | // We don't touch any particle above the cut momentum |
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75 | // |
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76 | if (particle->GetTotalMomentum() > minMomentum) return DBL_MAX; |
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77 | |
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78 | // |
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79 | // Nor do we touch any particle with small transverse component |
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80 | // to their momentum. Here the cutoff is somewhat arbitrary. |
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81 | // |
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82 | G4double vperp = track.GetMomentumDirection().perp(); |
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83 | if (vperp < 0.1) return DBL_MAX; |
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84 | |
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85 | // |
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86 | // How far in azimuthal angle do we need to go before the |
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87 | // particle loops back on itself? |
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88 | // |
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89 | G4ThreeVector initialDir(track.GetVertexMomentumDirection()); |
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90 | G4ThreeVector dx = track.GetPosition() - track.GetVertexPosition(); |
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91 | G4double dxPerp = dx.perp(); |
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92 | if (dxPerp < 1E-6) return DBL_MAX; |
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93 | |
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94 | G4double dot = ( initialDir.x()*dx.x() + initialDir.y()*dx.y() )/dxPerp; |
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95 | |
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96 | if (dot < 0) return 0; // Already done so |
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97 | |
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98 | G4double phi = pi - std::acos(dot); |
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99 | |
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100 | if (phi < 0) return 0; |
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101 | |
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102 | // |
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103 | // What is the radius of curvature? |
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104 | // |
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105 | // Only use the z component of the field to calculate this. |
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106 | // |
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107 | G4FieldManager *fieldManager = G4TransportationManager::GetTransportationManager()->GetFieldManager(); |
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108 | |
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109 | if (!fieldManager->DoesFieldExist()) return DBL_MAX; |
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110 | |
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111 | // |
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112 | // Assume the field is a magnetic field (i.e. returns |
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113 | // a vector of three doubles of unit Telsa). |
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114 | // |
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115 | // There is no good way I know to confirm this, so it is purely |
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116 | // a matter of faith. *** BEWARE *** |
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117 | // |
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118 | G4MagneticField *field = (G4MagneticField *)fieldManager->GetDetectorField(); |
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119 | G4double b[3]; |
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120 | G4ThreeVector pos(track.GetPosition()); |
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121 | G4double posv[3] = { pos.x(), pos.y(), pos.z() }; |
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122 | field->GetFieldValue( posv, b ); |
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123 | |
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124 | // |
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125 | // No field? Forget it! |
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126 | // |
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127 | if (std::fabs(b[2]) < 0.00001) return DBL_MAX; |
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128 | |
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129 | // |
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130 | // Calculate radius of curvature, the usual way. |
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131 | // Note G4 default units: mm, Telsa, MeV |
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132 | // |
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133 | // G4 suggestion: the constant below should be added to |
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134 | // the geant4 list. |
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135 | // |
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136 | G4double radius = std::fabs(track.GetMomentum().perp()/299.79251/b[2]); |
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137 | |
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138 | // |
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139 | // Convert this to a distance |
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140 | // |
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141 | return radius*phi/vperp; |
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142 | } |
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143 | |
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144 | |
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145 | // |
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146 | // PostStepDoit |
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147 | // |
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148 | G4VParticleChange * |
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149 | NTSTLooperDeath::PostStepDoIt( const G4Track &track, const G4Step & ) // step ) |
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150 | { |
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151 | pParticleChange->Initialize(track); |
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152 | |
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153 | // |
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154 | // This is a tough one. What should happen when we kill off a looper? |
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155 | // For now: just deposit remaining energy (including mass). |
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156 | // |
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157 | const G4DynamicParticle *particle = track.GetDynamicParticle(); |
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158 | G4double energyDeposited = particle->GetTotalEnergy(); |
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159 | |
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160 | pParticleChange->ProposeTrackStatus( fStopAndKill ); |
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161 | pParticleChange->SetNumberOfSecondaries( 0 ); |
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162 | pParticleChange->ProposeLocalEnergyDeposit( energyDeposited ); |
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163 | ClearNumberOfInteractionLengthLeft(); |
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164 | |
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165 | return pParticleChange; |
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166 | } |
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167 | |
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168 | |
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169 | |
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170 | |
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171 | |
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172 | |
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