| Geant4 Cross Reference |
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25 //
26 //
27 //
28
29 #include "G4PionDecayMakeSpin.hh"
30
31 #include "G4Decay.hh"
32 #include "G4DecayProducts.hh"
33
34 #include "G4RandomDirection.hh"
35
36 // constructor
37
38 G4PionDecayMakeSpin::G4PionDecayMakeSpin(const G4String& processName)
39 : G4Decay(processName)
40 {
41 // set Process Sub Type
42 SetProcessSubType(static_cast<int>(DECAY_PionMakeSpin));
43
44 }
45
46 G4PionDecayMakeSpin::~G4PionDecayMakeSpin() { }
47
48 void G4PionDecayMakeSpin::DaughterPolarization(const G4Track& aTrack,
49 G4DecayProducts* products)
50 {
51 // This routine deals only with particles that can decay into a muon
52 // pi+, pi-, K+, K- and K0_long
53
54 // get particle
55
56 const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
57 const G4ParticleDefinition* aParticleDef = aParticle->GetDefinition();
58
59 G4ParticleDefinition* aMuonPlus =
60 G4ParticleTable::GetParticleTable()->FindParticle("mu+");
61 G4ParticleDefinition* aMuonMinus =
62 G4ParticleTable::GetParticleTable()->FindParticle("mu-");
63 G4ParticleDefinition* aPionPlus =
64 G4ParticleTable::GetParticleTable()->FindParticle("pi+");
65 G4ParticleDefinition* aPionMinus =
66 G4ParticleTable::GetParticleTable()->FindParticle("pi-");
67 G4ParticleDefinition* aKaonPlus =
68 G4ParticleTable::GetParticleTable()->FindParticle("kaon+");
69 G4ParticleDefinition* aKaonMinus =
70 G4ParticleTable::GetParticleTable()->FindParticle("kaon-");
71 G4ParticleDefinition* aKaon0Long =
72 G4ParticleTable::GetParticleTable()->FindParticle("kaon0L");
73 G4ParticleDefinition* aNeutrinoMu =
74 G4ParticleTable::GetParticleTable()->FindParticle("nu_mu");
75 G4ParticleDefinition* aAntiNeutrinoMu =
76 G4ParticleTable::GetParticleTable()->FindParticle("anti_nu_mu");
77
78 if( aParticleDef == aPionPlus ||
79 aParticleDef == aPionMinus ||
80 aParticleDef == aKaonPlus ||
81 aParticleDef == aKaonMinus ||
82 aParticleDef == aKaon0Long ) {
83 } else {
84 return;
85 }
86
87 G4DynamicParticle* aMuon = nullptr;
88
89 G4double emu(0), eneutrino(0);
90 G4ThreeVector p_muon, p_neutrino;
91
92 G4int numberOfSecondaries = products->entries();
93
94 if (numberOfSecondaries > 0) {
95 for (G4int index=0; index < numberOfSecondaries; index++){
96 G4DynamicParticle* aSecondary = (*products)[index];
97 const G4ParticleDefinition* aSecondaryDef = aSecondary->GetDefinition();
98
99 if (aSecondaryDef == aMuonPlus ||
100 aSecondaryDef == aMuonMinus ) {
101 // Muon+ or Muon-
102 aMuon = aSecondary;
103 emu = aSecondary->GetTotalEnergy();
104 p_muon = aSecondary->GetMomentum();
105 } else if (aSecondaryDef == aNeutrinoMu ||
106 aSecondaryDef == aAntiNeutrinoMu ) {
107 // Muon-Neutrino / Muon-Anti-Neutrino
108 eneutrino = aSecondary->GetTotalEnergy();
109 p_neutrino = aSecondary->GetMomentum();
110 }
111 }
112 }
113
114 // This routine deals only with decays with a
115 // muon and mu-(anti)neutrinos in the final state
116 if (aMuon == nullptr) return;
117 if (eneutrino==0||emu==0) return;
118
119 G4ThreeVector spin(0,0,0);
120
121 const G4DynamicParticle* theParentParticle = products->GetParentParticle();
122
123 G4double amass = theParentParticle->GetMass();
124 G4double emmu = aMuonPlus->GetPDGMass();
125
126 if (numberOfSecondaries == 2 ) {
127 G4double scale = - (eneutrino - ( p_muon * p_neutrino )/(emu+emmu));
128
129 p_muon = scale * p_muon;
130 p_neutrino = emmu * p_neutrino;
131 spin = p_muon + p_neutrino;
132
133 scale = 2./(amass*amass-emmu*emmu);
134 spin = scale * spin;
135
136 if (aParticle->GetCharge() < 0.0) spin = -spin;
137
138 } else {
139 spin = G4RandomDirection();
140
141 }
142
143 spin = spin.unit();
144
145 aMuon->SetPolarization(spin.x(),spin.y(),spin.z());
146
147 return;
148 }
149
150 void G4PionDecayMakeSpin::ProcessDescription(std::ostream& outFile) const
151 {
152 outFile << GetProcessName()
153 << ": Decay of mesons that can decay into a muon \n"
154 << " i.e. pi+, pi-, K+, K- and K0_long \n"
155 << " kinematics of daughters are dertermined by DecayChannels \n"
156 << " polarization of daughter particles are take into account. \n";
157 }
158
159