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 | // |
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28 | |
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29 | #include "G4PionDecayMakeSpin.hh" |
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30 | |
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31 | #include "G4Decay.hh" |
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32 | #include "G4DecayProducts.hh" |
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33 | |
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34 | #include "G4RandomDirection.hh" |
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35 | |
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36 | // constructor |
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37 | |
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38 | G4PionDecayMakeSpin::G4PionDecayMakeSpin(const G4String& processName) |
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39 | : G4Decay(processName) |
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40 | { |
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41 | // set Process Sub Type |
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42 | SetProcessSubType(static_cast<int>(DECAY_PionMakeSpin)); |
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43 | |
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44 | } |
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45 | |
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46 | G4PionDecayMakeSpin::~G4PionDecayMakeSpin() { } |
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47 | |
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48 | void G4PionDecayMakeSpin::DaughterPolarization(const G4Track& aTrack, |
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49 | G4DecayProducts* products) |
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50 | { |
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51 | // This routine deals only with particles that can decay into a muon |
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52 | // pi+, pi-, K+, K- and K0_long |
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53 | |
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54 | // get particle |
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55 | |
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56 | const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle(); |
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57 | const G4ParticleDefinition* aParticleDef = aParticle->GetDefinition(); |
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58 | |
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59 | G4ParticleDefinition* aMuonPlus = |
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60 | G4ParticleTable::GetParticleTable()->FindParticle("mu+"); |
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61 | G4ParticleDefinition* aMuonMinus = |
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62 | G4ParticleTable::GetParticleTable()->FindParticle("mu-"); |
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63 | G4ParticleDefinition* aPionPlus = |
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64 | G4ParticleTable::GetParticleTable()->FindParticle("pi+"); |
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65 | G4ParticleDefinition* aPionMinus = |
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66 | G4ParticleTable::GetParticleTable()->FindParticle("pi-"); |
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67 | G4ParticleDefinition* aKaonPlus = |
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68 | G4ParticleTable::GetParticleTable()->FindParticle("kaon+"); |
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69 | G4ParticleDefinition* aKaonMinus = |
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70 | G4ParticleTable::GetParticleTable()->FindParticle("kaon-"); |
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71 | G4ParticleDefinition* aKaon0Long = |
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72 | G4ParticleTable::GetParticleTable()->FindParticle("kaon0L"); |
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73 | G4ParticleDefinition* aNeutrinoMu = |
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74 | G4ParticleTable::GetParticleTable()->FindParticle("nu_mu"); |
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75 | G4ParticleDefinition* aAntiNeutrinoMu = |
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76 | G4ParticleTable::GetParticleTable()->FindParticle("anti_nu_mu"); |
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77 | |
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78 | if( aParticleDef == aPionPlus || |
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79 | aParticleDef == aPionMinus || |
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80 | aParticleDef == aKaonPlus || |
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81 | aParticleDef == aKaonMinus || |
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82 | aParticleDef == aKaon0Long ) { |
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83 | } else { |
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84 | return; |
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85 | } |
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86 | |
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87 | G4DynamicParticle* aMuon = NULL; |
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88 | |
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89 | G4double emu(0), eneutrino(0); |
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90 | G4ThreeVector p_muon, p_neutrino; |
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91 | |
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92 | G4int numberOfSecondaries = products->entries(); |
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93 | |
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94 | if (numberOfSecondaries > 0) { |
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95 | for (G4int index=0; index < numberOfSecondaries; index++) |
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96 | { |
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97 | G4DynamicParticle* aSecondary = (*products)[index]; |
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98 | G4ParticleDefinition* aSecondaryDef = aSecondary->GetDefinition(); |
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99 | |
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100 | if (aSecondaryDef == aMuonPlus || |
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101 | aSecondaryDef == aMuonMinus ) { |
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102 | // Muon+ or Muon- |
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103 | aMuon = aSecondary; |
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104 | emu = aSecondary->GetTotalEnergy(); |
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105 | p_muon = aSecondary->GetMomentum(); |
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106 | } else if (aSecondaryDef == aNeutrinoMu || |
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107 | aSecondaryDef == aAntiNeutrinoMu ) { |
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108 | // Muon-Neutrino / Muon-Anti-Neutrino |
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109 | eneutrino = aSecondary->GetTotalEnergy(); |
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110 | p_neutrino = aSecondary->GetMomentum(); |
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111 | } |
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112 | } |
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113 | } |
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114 | |
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115 | // This routine deals only with decays with a |
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116 | // muon and mu-(anti)neutrinos in the final state |
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117 | |
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118 | if (!aMuon) return; |
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119 | if (eneutrino==0||emu==0) return; |
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120 | |
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121 | G4ThreeVector spin(0,0,0); |
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122 | |
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123 | const G4DynamicParticle* theParentParticle = products->GetParentParticle(); |
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124 | |
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125 | G4double amass = theParentParticle->GetMass(); |
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126 | G4double emmu = aMuonPlus->GetPDGMass(); |
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127 | |
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128 | if (numberOfSecondaries == 2 ) { |
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129 | |
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130 | G4double scale = - (eneutrino - ( p_muon * p_neutrino )/(emu+emmu)); |
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131 | |
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132 | p_muon = scale * p_muon; |
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133 | p_neutrino = emmu * p_neutrino; |
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134 | spin = p_muon + p_neutrino; |
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135 | |
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136 | scale = 2./(amass*amass-emmu*emmu); |
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137 | spin = scale * spin; |
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138 | |
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139 | if (aParticle->GetCharge() < 0.0) spin = -spin; |
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140 | |
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141 | } else { |
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142 | |
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143 | spin = G4RandomDirection(); |
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144 | |
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145 | } |
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146 | |
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147 | spin = spin.unit(); |
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148 | |
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149 | aMuon->SetPolarization(spin.x(),spin.y(),spin.z()); |
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150 | |
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151 | return; |
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152 | } |
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