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27 // -------------------------------------------------------------------
28 // GEANT 4 class file
29 //
30 // CERN, Geneva, Switzerland
31 //
32 // File name: G4GammaTransition
33 //
34 // Author V.Ivanchenko 27 February 2015
35 //
36 // -------------------------------------------------------------------
37
38 #include "G4GammaTransition.hh"
39 #include "G4AtomicShells.hh"
40 #include "Randomize.hh"
41 #include "G4RandomDirection.hh"
42 #include "G4Gamma.hh"
43 #include "G4Electron.hh"
44 #include "G4LorentzVector.hh"
45 #include "G4SystemOfUnits.hh"
46 #include "G4PhysicalConstants.hh"
47
48 G4GammaTransition::G4GammaTransition()
49 : polarFlag(false), fDirection(0.,0.,0.), fTwoJMAX(10), fVerbose(0)
50 {}
51
52 G4GammaTransition::~G4GammaTransition()
53 {}
54
55 G4Fragment*
56 G4GammaTransition::SampleTransition(G4Fragment* nucleus,
57 G4double newExcEnergy,
58 G4double mpRatio,
59 G4int JP1,
60 G4int JP2,
61 G4int MP,
62 G4int shell,
63 G4bool isDiscrete,
64 G4bool isGamma)
65 {
66 G4Fragment* result = nullptr;
67 G4double bond_energy = 0.0;
68
69 if (!isGamma) {
70 if(0 <= shell) {
71 G4int Z = nucleus->GetZ_asInt();
72 if(Z <= 104) {
73 G4int idx = std::min(shell, G4AtomicShells::GetNumberOfShells(Z)-1);
74 bond_energy = G4AtomicShells::GetBindingEnergy(Z, idx);
75 }
76 }
77 }
78 G4double etrans = nucleus->GetExcitationEnergy() - newExcEnergy
79 - bond_energy;
80 if(fVerbose > 2) {
81 G4cout << "G4GammaTransition::GenerateGamma - Etrans(MeV)= "
82 << etrans << " Eexnew= " << newExcEnergy
83 << " Ebond= " << bond_energy << G4endl;
84 }
85 if(etrans <= 0.0) {
86 etrans += bond_energy;
87 bond_energy = 0.0;
88 }
89
90 // Do complete Lorentz computation
91 G4LorentzVector lv = nucleus->GetMomentum();
92 G4double mass = nucleus->GetGroundStateMass() + newExcEnergy;
93
94 // select secondary
95 G4ParticleDefinition* part;
96
97 if(isGamma) { part = G4Gamma::Gamma(); }
98 else {
99 part = G4Electron::Electron();
100 G4int ne = std::max(nucleus->GetNumberOfElectrons() - 1, 0);
101 nucleus->SetNumberOfElectrons(ne);
102 }
103
104 if(polarFlag && isDiscrete && JP1 <= fTwoJMAX) {
105 SampleDirection(nucleus, mpRatio, JP1, JP2, MP);
106 } else {
107 fDirection = G4RandomDirection();
108 }
109
110 G4double emass = part->GetPDGMass();
111
112 // 2-body decay in rest frame
113 G4double ecm = lv.mag();
114 G4ThreeVector bst = lv.boostVector();
115 if(!isGamma) { ecm += (CLHEP::electron_mass_c2 - bond_energy); }
116
117 //G4cout << "Ecm= " << ecm << " mass= " << mass << " emass= " << emass << G4endl;
118
119 ecm = std::max(ecm, mass + emass);
120 G4double energy = 0.5*((ecm - mass)*(ecm + mass) + emass*emass)/ecm;
121 G4double mom = (emass > 0.0) ? std::sqrt((energy - emass)*(energy + emass))
122 : energy;
123
124 // emitted gamma or e-
125 G4LorentzVector res4mom(mom * fDirection.x(),
126 mom * fDirection.y(),
127 mom * fDirection.z(), energy);
128 // residual
129 energy = std::max(ecm - energy, mass);
130 lv.set(-mom*fDirection.x(), -mom*fDirection.y(), -mom*fDirection.z(), energy);
131
132 // Lab system transform for short lived level
133 lv.boost(bst);
134
135 // modified primary fragment
136 nucleus->SetExcEnergyAndMomentum(newExcEnergy, lv);
137
138 // gamma or e- are produced
139 res4mom.boost(bst);
140 result = new G4Fragment(res4mom, part);
141
142 //G4cout << " DeltaE= " << e0 - lv.e() - res4mom.e() + emass
143 // << " Emass= " << emass << G4endl;
144 if(fVerbose > 2) {
145 G4cout << "G4GammaTransition::SampleTransition : " << *result << G4endl;
146 G4cout << " Left nucleus: " << *nucleus << G4endl;
147 }
148 return result;
149 }
150
151 void G4GammaTransition::SampleDirection(G4Fragment* nuc, G4double ratio,
152 G4int twoJ1, G4int twoJ2, G4int mp)
153 {
154 G4double cosTheta, phi;
155 G4NuclearPolarization* np = nuc->GetNuclearPolarization();
156 if(fVerbose > 2) {
157 G4cout << "G4GammaTransition::SampleDirection : 2J1= " << twoJ1
158 << " 2J2= " << twoJ2 << " ratio= " << ratio
159 << " mp= " << mp << G4endl;
160 G4cout << " Nucleus: " << *nuc << G4endl;
161 }
162 if(nullptr == np) {
163 cosTheta = 2*G4UniformRand() - 1.0;
164 phi = CLHEP::twopi*G4UniformRand();
165
166 } else {
167 // PhotonEvaporation dataset:
168 // The multipolarity number with 1,2,3,4,5,6,7 representing E0,E1,M1,E2,M2,E3,M3
169 // monopole transition and 100*Nx+Ny representing multipolarity transition with
170 // Ny and Ny taking the value 1,2,3,4,5,6,7 referring to E0,E1,M1,E2,M2,E3,M3,..
171 // For example a M1+E2 transition would be written 304.
172 // M1 is the primary transition (L) and E2 is the secondary (L')
173
174 G4double mpRatio = ratio;
175
176 G4int L0 = 0, Lp = 0;
177 if (mp > 99) {
178 L0 = mp/200;
179 Lp = (mp%100)/2;
180 } else {
181 L0 = mp/2;
182 Lp = 0;
183 mpRatio = 0.;
184 }
185 fPolTrans.SampleGammaTransition(np, twoJ1, twoJ2, L0, Lp, mpRatio, cosTheta, phi);
186 }
187
188 G4double sinTheta = std::sqrt((1.-cosTheta)*(1.+cosTheta));
189 fDirection.set(sinTheta*std::cos(phi),sinTheta*std::sin(phi),cosTheta);
190 if(fVerbose > 3) {
191 G4cout << "G4GammaTransition::SampleDirection done: " << fDirection << G4endl;
192 if(np) { G4cout << *np << G4endl; }
193 }
194 }
195