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25 //
26 ////////////////////////////////////////////////////////////////////////////////
27 // //
28 // File: G4BetaPlusDecay.cc //
29 // Author: D.H. Wright (SLAC) //
30 // Date: 14 November 2014 //
31 // Modifications: //
32 // 23.08.2023 V.Ivanchenko //
33 // //
34 ////////////////////////////////////////////////////////////////////////////////
35
36 #include "G4BetaPlusDecay.hh"
37 #include "G4BetaDecayCorrections.hh"
38 #include "G4IonTable.hh"
39 #include "G4ThreeVector.hh"
40 #include "G4LorentzVector.hh"
41 #include "G4DynamicParticle.hh"
42 #include "G4DecayProducts.hh"
43 #include "G4PhysicalConstants.hh"
44 #include "G4SystemOfUnits.hh"
45 #include "G4Positron.hh"
46 #include "G4NeutrinoE.hh"
47 #include "G4RandomDirection.hh"
48 #include "G4BetaSpectrumSampler.hh"
49 #include <iostream>
50 #include <iomanip>
51
52 namespace {
53 const G4double eMass = CLHEP::electron_mass_c2;
54 }
55
56 G4BetaPlusDecay::G4BetaPlusDecay(const G4ParticleDefinition* theParentNucleus,
57 const G4double& branch, const G4double& e0,
58 const G4double& excitationE,
59 const G4Ions::G4FloatLevelBase& flb,
60 const G4BetaDecayType& betaType)
61 : G4NuclearDecay("beta+ decay", BetaPlus, excitationE, flb),
62 maxEnergy(e0/eMass - 2.0),
63 estep(maxEnergy/(G4double)(npti - 1))
64 {
65 SetParent(theParentNucleus); // Store name of parent nucleus, delete G4MT_parent
66 SetBR(branch);
67 SetNumberOfDaughters(3);
68
69 fPrimaryIon = theParentNucleus;
70 fLepton = G4Positron::Positron();
71 fNeutrino = G4NeutrinoE::NeutrinoE();
72
73 G4IonTable* theIonTable = G4ParticleTable::GetParticleTable()->GetIonTable();
74 G4int daughterZ = theParentNucleus->GetAtomicNumber() - 1;
75 G4int daughterA = theParentNucleus->GetAtomicMass();
76 fResIon = const_cast<const G4ParticleDefinition*>(theIonTable->GetIon(daughterZ, daughterA,
77 excitationE, flb));
78
79 parentMass = theParentNucleus->GetPDGMass();
80 resMass = fResIon->GetPDGMass();
81
82 SetUpBetaSpectrumSampler(daughterZ, daughterA, betaType);
83
84 SetDaughter(0, fResIon);
85 SetDaughter(1, fLepton);
86 SetDaughter(2, fNeutrino);
87
88 // Fill G4MT_parent with theParentNucleus (stored by SetParent in ctor)
89 CheckAndFillParent();
90
91 // Fill G4MT_daughters with e+, nu and residual nucleus (stored by SetDaughter)
92 CheckAndFillDaughters();
93 }
94
95 G4DecayProducts* G4BetaPlusDecay::DecayIt(G4double)
96 {
97 // Set up final state
98 // parentParticle is set at rest here because boost with correct momentum
99 // is done later
100 G4DynamicParticle prim(fPrimaryIon, G4ThreeVector(0,0,1), 0.0);
101 G4DecayProducts* products = new G4DecayProducts(prim);
102
103 // Generate positron isotropic in angle, with energy from stored spectrum
104 const G4double eKE = eMass*G4BetaSpectrumSampler::shoot(npti, cdf, estep);
105
106 G4double eMomentum = std::sqrt(eKE*(eKE + 2.*eMass));
107 G4ThreeVector dir = G4RandomDirection();
108 G4DynamicParticle* dp = new G4DynamicParticle(fLepton, dir, eKE);
109 products->PushProducts(dp);
110 /*
111 G4cout << "G4BetaPlusDecay::DecayIt: " << fPrimaryIon->GetParticleName()
112 << " -> " << fResIon->GetParticleName() << " + " << fLepton->GetParticleName()
113 << " + " << fNeutrino->GetParticleName() << " Ee(MeV)=" << eKE
114 << G4endl;
115 */
116 // 4-momentum of residual ion and neutrino
117 G4LorentzVector lv(-eMomentum*dir.x(), -eMomentum*dir.y(), -eMomentum*dir.z(),
118 parentMass - eKE - eMass);
119
120 const G4double elim = CLHEP::eV;
121 // centrum of mass system
122 G4double M = lv.mag();
123 G4double edel = M - resMass;
124 // Free energy should be above limit
125 if (edel >= elim) {
126 // neutrino
127 G4double eNu = 0.5*(M - resMass*resMass/M);
128 G4LorentzVector lvnu(eNu*G4RandomDirection(), eNu);
129 lvnu.boost(lv.boostVector());
130 dir = lvnu.vect().unit();
131 dp = new G4DynamicParticle(fNeutrino, dir, lvnu.e());
132 products->PushProducts(dp);
133
134 // residual
135 lv -= lvnu;
136 dir = lv.vect().unit();
137 G4double ekin = std::max(lv.e() - resMass, 0.0);
138 dp = new G4DynamicParticle(fResIon, dir, ekin);
139 products->PushProducts(dp);
140
141 } else {
142 // neglecting relativistic kinematic and giving all energy to neutrino
143 dp = new G4DynamicParticle(fNeutrino, G4RandomDirection(), elim);
144 products->PushProducts(dp);
145 dp = new G4DynamicParticle(fResIon, G4ThreeVector(0.0,0.0,1.0), 0.0);
146 products->PushProducts(dp);
147 }
148
149 return products;
150 }
151
152
153 void
154 G4BetaPlusDecay::SetUpBetaSpectrumSampler(const G4int& daughterZ,
155 const G4int& daughterA,
156 const G4BetaDecayType& betaType)
157 {
158 cdf[0] = 0.0;
159
160 // Check for cases in which Q < 2Me (e.g. z67.a162)
161 if (maxEnergy > 0.) {
162 G4BetaDecayCorrections corrections(-daughterZ, daughterA);
163
164 // Fill array to store cumulative spectrum
165 G4double ex; // Positron kinetic energy
166 G4double p; // Positron momentum in units of electron mass
167 G4double f; // Spectral shape function
168 G4double f0 = 0.0;
169 G4double sum = 0.0;
170 for (G4int i = 1; i < npti-1; ++i) {
171 ex = estep*i;
172 p = std::sqrt(ex*(ex + 2.));
173 f = p*(1. + ex)*(maxEnergy - ex)*(maxEnergy - ex);
174
175 // Apply Fermi factor to get allowed shape
176 f *= corrections.FermiFunction(1. + ex);
177
178 // Apply shape factor for forbidden transitions
179 f *= corrections.ShapeFactor(betaType, p, maxEnergy - ex);
180 sum += f + f0;
181 cdf[i] = sum;
182 f0 = f;
183 }
184 cdf[npti-1] = sum + f0;
185 } else {
186 for (G4int i = 0; i < npti; ++i) { cdf[i] = 0.0; }
187 }
188 }
189
190 void G4BetaPlusDecay::DumpNuclearInfo()
191 {
192 G4cout << " G4BetaPlusDecay " << fPrimaryIon->GetParticleName()
193 << " -> " << fResIon->GetParticleName() << " + " << fLepton->GetParticleName()
194 << " + " << fNeutrino->GetParticleName() << " Eemax(MeV)="
195 << maxEnergy*eMass << " BR=" << GetBR() << "%" << G4endl;
196 }
197