| Geant4 Cross Reference |
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25 //
26 // ------------------------------------------------------------
27 // GEANT 4 class header file
28 //
29 // History:
30 // 17 August 2004 P. Gumplinger, T. MacPhail
31 // 11 April 2008 Kamil Sedlak (PSI), Toni Shiroka (PSI)
32 // ------------------------------------------------------------
33 //
34 #include "G4DecayWithSpin.hh"
35
36 #include "G4Step.hh"
37 #include "G4Track.hh"
38 #include "G4DecayTable.hh"
39 #include "G4MuonDecayChannelWithSpin.hh"
40
41 #include "G4PhysicalConstants.hh"
42 #include "G4SystemOfUnits.hh"
43 #include "G4Vector3D.hh"
44
45 #include "G4TransportationManager.hh"
46 #include "G4PropagatorInField.hh"
47 #include "G4FieldManager.hh"
48 #include "G4Field.hh"
49
50 #include "G4Transform3D.hh"
51
52 G4DecayWithSpin::G4DecayWithSpin(const G4String& processName):G4Decay(processName)
53 {
54 // set Process Sub Type
55 SetProcessSubType(static_cast<int>(DECAY_WithSpin));
56
57 }
58
59 G4DecayWithSpin::~G4DecayWithSpin(){}
60
61 G4VParticleChange* G4DecayWithSpin::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)
62 {
63 if ( (aTrack.GetTrackStatus() == fStopButAlive ) ||
64 (aTrack.GetTrackStatus() == fStopAndKill ) ){
65 fParticleChangeForDecay.Initialize(aTrack);
66 return &fParticleChangeForDecay;
67 }
68
69 // get particle
70 const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
71 const G4ParticleDefinition* aParticleDef = aParticle->GetDefinition();
72
73 // get parent_polarization
74 G4ThreeVector parent_polarization = aParticle->GetPolarization();
75
76 if(parent_polarization == G4ThreeVector(0,0,0)){
77 // Generate random polarization direction
78 G4double cost = 1. - 2.*G4UniformRand();
79 G4double sint = std::sqrt((1.-cost)*(1.+cost));
80
81 G4double phi = twopi*G4UniformRand();
82 G4double sinp = std::sin(phi);
83 G4double cosp = std::cos(phi);
84
85 G4double px = sint*cosp;
86 G4double py = sint*sinp;
87 G4double pz = cost;
88
89 parent_polarization.setX(px);
90 parent_polarization.setY(py);
91 parent_polarization.setZ(pz);
92 }
93
94 // decay table
95 G4DecayTable *decaytable = aParticleDef->GetDecayTable();
96 if (decaytable != nullptr) {
97 for (G4int ip=0; ip<decaytable->entries(); ip++){
98 decaytable->GetDecayChannel(ip)->SetPolarization(parent_polarization);
99 }
100 }
101
102 G4ParticleChangeForDecay* pParticleChangeForDecay;
103 pParticleChangeForDecay = (G4ParticleChangeForDecay*)G4Decay::DecayIt(aTrack,aStep);
104 pParticleChangeForDecay->ProposePolarization(parent_polarization);
105
106 return pParticleChangeForDecay;
107 }
108
109 G4VParticleChange* G4DecayWithSpin::AtRestDoIt(const G4Track& aTrack, const G4Step& aStep)
110 {
111
112 // get particle
113 const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
114 const G4ParticleDefinition* aParticleDef = aParticle->GetDefinition();
115
116 // get parent_polarization
117 G4ThreeVector parent_polarization = aParticle->GetPolarization();
118
119 if(parent_polarization == G4ThreeVector(0,0,0)) {
120 // Generate random polarization direction
121 G4double cost = 1. - 2.*G4UniformRand();
122 G4double sint = std::sqrt((1.-cost)*(1.+cost));
123
124 G4double phi = twopi*G4UniformRand();
125 G4double sinp = std::sin(phi);
126 G4double cosp = std::cos(phi);
127
128 G4double px = sint*cosp;
129 G4double py = sint*sinp;
130 G4double pz = cost;
131
132 parent_polarization.setX(px);
133 parent_polarization.setY(py);
134 parent_polarization.setZ(pz);
135
136 }else{
137
138 G4FieldManager* fieldMgr = aStep.GetTrack()->GetVolume()->
139 GetLogicalVolume()->GetFieldManager();
140 if (fieldMgr == nullptr) {
141 G4TransportationManager *transportMgr =
142 G4TransportationManager::GetTransportationManager();
143 G4PropagatorInField* fFieldPropagator =
144 transportMgr->GetPropagatorInField();
145 if (fFieldPropagator) fieldMgr =
146 fFieldPropagator->GetCurrentFieldManager();
147 }
148
149 const G4Field* field = nullptr;
150 if (fieldMgr != nullptr) field = fieldMgr->GetDetectorField();
151
152 if ( field != nullptr ) {
153 G4double point[4];
154 point[0] = (aStep.GetPostStepPoint()->GetPosition())[0];
155 point[1] = (aStep.GetPostStepPoint()->GetPosition())[1];
156 point[2] = (aStep.GetPostStepPoint()->GetPosition())[2];
157 point[3] = aTrack.GetGlobalTime();
158
159 G4double fieldValue[6] ={ 0., 0., 0., 0., 0., 0.};
160 field -> GetFieldValue(point,fieldValue);
161 G4ThreeVector B(fieldValue[0],fieldValue[1],fieldValue[2]);
162
163 // Call the spin precession only for non-zero mag. field
164 if (B.mag2() > 0.) parent_polarization =
165 Spin_Precession(aStep,B,fRemainderLifeTime);
166
167 }
168 }
169
170 // decay table
171 G4DecayTable *decaytable = aParticleDef->GetDecayTable();
172 if ( decaytable != nullptr) {
173 for (G4int ip=0; ip<decaytable->entries(); ip++){
174 decaytable->GetDecayChannel(ip)->SetPolarization(parent_polarization);
175 }
176 }
177
178 G4ParticleChangeForDecay* pParticleChangeForDecay;
179 pParticleChangeForDecay = (G4ParticleChangeForDecay*)G4Decay::DecayIt(aTrack,aStep);
180 pParticleChangeForDecay->ProposePolarization(parent_polarization);
181
182 return pParticleChangeForDecay;
183
184 }
185
186 G4ThreeVector G4DecayWithSpin::Spin_Precession( const G4Step& aStep,
187 G4ThreeVector B, G4double deltatime )
188 {
189 G4double Bnorm = std::sqrt(sqr(B[0]) + sqr(B[1]) +sqr(B[2]) );
190
191 G4double q = aStep.GetTrack()->GetDefinition()->GetPDGCharge();
192 G4double a = 1.165922e-3;
193 G4double s_omega = 8.5062e+7*rad/(s*kilogauss);
194
195 G4double omega = -(q*s_omega)*(1.+a) * Bnorm;
196
197 G4double rotationangle = deltatime * omega;
198
199 G4Transform3D SpinRotation = G4Rotate3D(rotationangle,B.unit());
200
201 G4Vector3D Spin = aStep.GetTrack() -> GetPolarization();
202
203 G4Vector3D newSpin = SpinRotation * Spin;
204
205 #ifdef G4VERBOSE
206 if (GetVerboseLevel()>2) {
207 G4double normspin = std::sqrt(Spin*Spin);
208 G4double normnewspin = std::sqrt(newSpin*newSpin);
209 //G4double cosalpha = Spin*newSpin/normspin/normnewspin;
210 //G4double alpha = std::acos(cosalpha);
211
212 G4cout << "AT REST::: PARAMETERS " << G4endl;
213 G4cout << "Initial spin : " << Spin << G4endl;
214 G4cout << "Delta time : " << deltatime << G4endl;
215 G4cout << "Rotation angle: " << rotationangle/rad << G4endl;
216 G4cout << "New spin : " << newSpin << G4endl;
217 G4cout << "Checked norms : " << normspin <<" " << normnewspin << G4endl;
218 }
219 #endif
220
221 return newSpin;
222
223 }
224
225 void G4DecayWithSpin::ProcessDescription(std::ostream& outFile) const
226 {
227 outFile << GetProcessName()
228 << ": Decay of particles considering parent polarization \n"
229 << "kinematics of daughters are dertermined by DecayChannels \n";
230 }
231