[819] | 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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[961] | 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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[819] | 43 | |
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[961] | 44 | } |
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| 45 | |
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[819] | 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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