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25 // 25 //
>> 26 // $Id: G4eeToTwoGammaModel.cc,v 1.15 2009-04-09 18:41:18 vnivanch Exp $
>> 27 // GEANT4 tag $Name: not supported by cvs2svn $
26 // 28 //
27 // ------------------------------------------- 29 // -------------------------------------------------------------------
28 // 30 //
29 // GEANT4 Class file 31 // GEANT4 Class file
30 // 32 //
31 // 33 //
32 // File name: G4eeToTwoGammaModel 34 // File name: G4eeToTwoGammaModel
33 // 35 //
34 // Author: Vladimir Ivanchenko on base 36 // Author: Vladimir Ivanchenko on base of Michel Maire code
35 // 37 //
36 // Creation date: 02.08.2004 38 // Creation date: 02.08.2004
37 // 39 //
38 // Modifications: 40 // Modifications:
39 // 08-04-05 Major optimisation of internal int 41 // 08-04-05 Major optimisation of internal interfaces (V.Ivanchenko)
40 // 18-04-05 Compute CrossSectionPerVolume (V.I 42 // 18-04-05 Compute CrossSectionPerVolume (V.Ivanchenko)
41 // 06-02-06 ComputeCrossSectionPerElectron, Co 43 // 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
42 // 29-06-06 Fix problem for zero energy incide 44 // 29-06-06 Fix problem for zero energy incident positron (V.Ivanchenko)
43 // 20-10-06 Add theGamma as a member (V.Ivanch 45 // 20-10-06 Add theGamma as a member (V.Ivanchenko)
44 // 18-01-20 Introduce thermal model of annihil <<
45 // 46 //
46 // 47 //
47 // Class Description: 48 // Class Description:
48 // 49 //
49 // Implementation of e+ annihilation into 2 ga 50 // Implementation of e+ annihilation into 2 gamma
50 // 51 //
51 // The secondaries Gamma energies are sampled 52 // The secondaries Gamma energies are sampled using the Heitler cross section.
52 // 53 //
53 // A modified version of the random number tec 54 // A modified version of the random number techniques of Butcher & Messel
54 // is used (Nuc Phys 20(1960),15). 55 // is used (Nuc Phys 20(1960),15).
55 // 56 //
56 // GEANT4 internal units. 57 // GEANT4 internal units.
57 // 58 //
58 // Note 1: The initial electron is assumed fre << 59 // Note 1: The initial electron is assumed free and at rest.
59 // is not defined <<
60 // 60 //
61 // Note 2: The annihilation processes producin 61 // Note 2: The annihilation processes producing one or more than two photons are
62 // ignored, as negligible compared to 62 // ignored, as negligible compared to the two photons process.
63 63
>> 64
>> 65
64 // 66 //
65 // ------------------------------------------- 67 // -------------------------------------------------------------------
66 // 68 //
67 //....oooOO0OOooo........oooOO0OOooo........oo 69 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
68 //....oooOO0OOooo........oooOO0OOooo........oo 70 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
69 71
70 #include "G4eeToTwoGammaModel.hh" 72 #include "G4eeToTwoGammaModel.hh"
71 #include "G4PhysicalConstants.hh" <<
72 #include "G4SystemOfUnits.hh" <<
73 #include "G4TrackStatus.hh" 73 #include "G4TrackStatus.hh"
74 #include "G4Electron.hh" 74 #include "G4Electron.hh"
75 #include "G4Positron.hh" 75 #include "G4Positron.hh"
76 #include "G4Gamma.hh" 76 #include "G4Gamma.hh"
77 #include "Randomize.hh" 77 #include "Randomize.hh"
78 #include "G4RandomDirection.hh" <<
79 #include "G4ParticleChangeForGamma.hh" 78 #include "G4ParticleChangeForGamma.hh"
80 #include "G4EmParameters.hh" <<
81 #include "G4Log.hh" <<
82 #include "G4Exp.hh" <<
83 79
84 //....oooOO0OOooo........oooOO0OOooo........oo 80 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
85 81
>> 82 using namespace std;
>> 83
86 G4eeToTwoGammaModel::G4eeToTwoGammaModel(const 84 G4eeToTwoGammaModel::G4eeToTwoGammaModel(const G4ParticleDefinition*,
87 const 85 const G4String& nam)
88 : G4VEmModel(nam), 86 : G4VEmModel(nam),
89 pi_rcl2(CLHEP::pi*CLHEP::classic_electr_ra << 87 pi_rcl2(pi*classic_electr_radius*classic_electr_radius),
>> 88 isInitialised(false)
90 { 89 {
91 theGamma = G4Gamma::Gamma(); 90 theGamma = G4Gamma::Gamma();
92 fParticleChange = nullptr; <<
93 } 91 }
94 92
95 //....oooOO0OOooo........oooOO0OOooo........oo 93 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
96 94
97 G4eeToTwoGammaModel::~G4eeToTwoGammaModel() = << 95 G4eeToTwoGammaModel::~G4eeToTwoGammaModel()
>> 96 {}
98 97
99 //....oooOO0OOooo........oooOO0OOooo........oo 98 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
100 99
101 void G4eeToTwoGammaModel::Initialise(const G4P 100 void G4eeToTwoGammaModel::Initialise(const G4ParticleDefinition*,
102 const G4D 101 const G4DataVector&)
103 { 102 {
104 if (nullptr != fParticleChange) { return; } << 103 if(isInitialised) return;
105 fParticleChange = GetParticleChangeForGamma( 104 fParticleChange = GetParticleChangeForGamma();
>> 105 isInitialised = true;
106 } 106 }
107 107
108 //....oooOO0OOooo........oooOO0OOooo........oo 108 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
109 109
110 G4double << 110 G4double G4eeToTwoGammaModel::ComputeCrossSectionPerElectron(
111 G4eeToTwoGammaModel::ComputeCrossSectionPerEle << 111 const G4ParticleDefinition*,
>> 112 G4double kineticEnergy,
>> 113 G4double, G4double)
112 { 114 {
113 // Calculates the cross section per electron 115 // Calculates the cross section per electron of annihilation into two photons
114 // from the Heilter formula. 116 // from the Heilter formula.
115 << 117
116 G4double ekin = std::max(CLHEP::eV, kinetic << 118 G4double tau = kineticEnergy/electron_mass_c2;
117 <<
118 G4double tau = ekin/CLHEP::electron_mass_c <<
119 G4double gam = tau + 1.0; 119 G4double gam = tau + 1.0;
120 G4double gamma2= gam*gam; 120 G4double gamma2= gam*gam;
121 G4double bg2 = tau * (tau+2.0); 121 G4double bg2 = tau * (tau+2.0);
122 G4double bg = std::sqrt(bg2); << 122 G4double bg = sqrt(bg2);
123 123
124 G4double cross = pi_rcl2*((gamma2+4*gam+1.)* << 124 G4double cross = pi_rcl2*((gamma2+4*gam+1.)*log(gam+bg) - (gam+3.)*bg)
125 / (bg2*(gam+1.)); 125 / (bg2*(gam+1.));
126 return cross; 126 return cross;
127 } 127 }
128 128
129 //....oooOO0OOooo........oooOO0OOooo........oo 129 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
130 130
131 G4double G4eeToTwoGammaModel::ComputeCrossSect 131 G4double G4eeToTwoGammaModel::ComputeCrossSectionPerAtom(
132 const G4Pa << 132 const G4ParticleDefinition* p,
133 G4double k 133 G4double kineticEnergy, G4double Z,
134 G4double, G4double, G4double) 134 G4double, G4double, G4double)
135 { 135 {
136 // Calculates the cross section per atom of 136 // Calculates the cross section per atom of annihilation into two photons
137 return Z*ComputeCrossSectionPerElectron(kine << 137
>> 138 G4double cross = Z*ComputeCrossSectionPerElectron(p,kineticEnergy);
>> 139 return cross;
138 } 140 }
139 141
140 //....oooOO0OOooo........oooOO0OOooo........oo 142 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
141 143
142 G4double G4eeToTwoGammaModel::CrossSectionPerV 144 G4double G4eeToTwoGammaModel::CrossSectionPerVolume(
143 const G4Material* material, 145 const G4Material* material,
144 const G4ParticleDefinition*, << 146 const G4ParticleDefinition* p,
145 G4double kineticEnergy, 147 G4double kineticEnergy,
146 G4double, G4double) 148 G4double, G4double)
147 { 149 {
148 // Calculates the cross section per volume o 150 // Calculates the cross section per volume of annihilation into two photons
149 return material->GetElectronDensity()*Comput << 151
>> 152 G4double eDensity = material->GetElectronDensity();
>> 153 G4double cross = eDensity*ComputeCrossSectionPerElectron(p,kineticEnergy);
>> 154 return cross;
150 } 155 }
151 156
152 //....oooOO0OOooo........oooOO0OOooo........oo 157 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
153 158
154 // Polarisation of gamma according to M.H.L.Pr << 159 void G4eeToTwoGammaModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
155 // Nature 4065 (1947) 435. <<
156 <<
157 void G4eeToTwoGammaModel::SampleSecondaries(st <<
158 const G4MaterialCutsCouple*, 160 const G4MaterialCutsCouple*,
159 const G4DynamicParticle* dp, 161 const G4DynamicParticle* dp,
160 G4double, 162 G4double,
161 G4double) 163 G4double)
162 { 164 {
163 // kill primary positron << 165 G4double PositKinEnergy = dp->GetKineticEnergy();
164 fParticleChange->SetProposedKineticEnergy(0. <<
165 fParticleChange->ProposeTrackStatus(fStopAnd <<
166 <<
167 // Case at rest not considered anymore insid <<
168 G4LorentzVector lv(dp->GetMomentum(), <<
169 dp->GetKineticEnergy() + 2*CLHEP::ele <<
170 G4double eGammaCMS = 0.5 * lv.mag(); <<
171 <<
172 G4ThreeVector dir1 = G4RandomDirection(); <<
173 G4double phi = CLHEP::twopi * G4UniformRand( <<
174 G4double cosphi = std::cos(phi); <<
175 G4double sinphi = std::sin(phi); <<
176 G4ThreeVector pol1(cosphi, sinphi, 0.0); <<
177 pol1.rotateUz(dir1); <<
178 G4LorentzVector lv1(eGammaCMS*dir1, eGammaCM <<
179 <<
180 G4ThreeVector pol2(-sinphi, cosphi, 0.0); <<
181 pol2.rotateUz(dir1); <<
182 <<
183 // transformation to lab system <<
184 lv1.boost(lv.boostVector()); <<
185 lv -= lv1; <<
186 166
187 //!!! boost of polarisation vector is not ye << 167 // Case at rest
188 << 168 if(PositKinEnergy == 0.0) {
189 // use constructors optimal for massless par << 169 G4double cost = 2.*G4UniformRand()-1.;
190 auto aGamma1 = new G4DynamicParticle(G4Gamma << 170 G4double sint = sqrt((1. - cost)*(1. + cost));
191 aGamma1->SetPolarization(pol1); << 171 G4double phi = twopi * G4UniformRand();
192 auto aGamma2 = new G4DynamicParticle(G4Gamma << 172 G4ThreeVector dir (sint*cos(phi), sint*sin(phi), cost);
193 aGamma2->SetPolarization(pol2); << 173 G4DynamicParticle* aGamma1 = new G4DynamicParticle(theGamma,
194 << 174 dir, electron_mass_c2);
195 vdp->push_back(aGamma1); << 175 G4DynamicParticle* aGamma2 = new G4DynamicParticle(theGamma,
196 vdp->push_back(aGamma2); << 176 -dir, electron_mass_c2);
>> 177 vdp->push_back(aGamma1);
>> 178 vdp->push_back(aGamma2);
>> 179
>> 180 } else {
>> 181
>> 182 G4ThreeVector PositDirection = dp->GetMomentumDirection();
>> 183
>> 184 G4double tau = PositKinEnergy/electron_mass_c2;
>> 185 G4double gam = tau + 1.0;
>> 186 G4double tau2 = tau + 2.0;
>> 187 G4double sqgrate = sqrt(tau/tau2)*0.5;
>> 188 G4double sqg2m1 = sqrt(tau*tau2);
>> 189
>> 190 // limits of the energy sampling
>> 191 G4double epsilmin = 0.5 - sqgrate;
>> 192 G4double epsilmax = 0.5 + sqgrate;
>> 193 G4double epsilqot = epsilmax/epsilmin;
>> 194
>> 195 //
>> 196 // sample the energy rate of the created gammas
>> 197 //
>> 198 G4double epsil, greject;
>> 199
>> 200 do {
>> 201 epsil = epsilmin*pow(epsilqot,G4UniformRand());
>> 202 greject = 1. - epsil + (2.*gam*epsil-1.)/(epsil*tau2*tau2);
>> 203 } while( greject < G4UniformRand() );
>> 204
>> 205 //
>> 206 // scattered Gamma angles. ( Z - axis along the parent positron)
>> 207 //
>> 208
>> 209 G4double cost = (epsil*tau2-1.)/(epsil*sqg2m1);
>> 210 if(std::abs(cost) > 1.0) {
>> 211 G4cout << "### G4eeToTwoGammaModel WARNING cost= " << cost
>> 212 << " positron Ekin(MeV)= " << PositKinEnergy
>> 213 << " gamma epsil= " << epsil
>> 214 << G4endl;
>> 215 if(cost > 1.0) cost = 1.0;
>> 216 else cost = -1.0;
>> 217 }
>> 218 G4double sint = sqrt((1.+cost)*(1.-cost));
>> 219 G4double phi = twopi * G4UniformRand();
>> 220
>> 221 G4double dirx = sint*cos(phi) , diry = sint*sin(phi) , dirz = cost;
>> 222
>> 223 //
>> 224 // kinematic of the created pair
>> 225 //
>> 226
>> 227 G4double TotalAvailableEnergy = PositKinEnergy + 2.0*electron_mass_c2;
>> 228 G4double Phot1Energy = epsil*TotalAvailableEnergy;
>> 229
>> 230 G4ThreeVector Phot1Direction (dirx, diry, dirz);
>> 231 Phot1Direction.rotateUz(PositDirection);
>> 232 G4DynamicParticle* aGamma1 =
>> 233 new G4DynamicParticle (theGamma,Phot1Direction, Phot1Energy);
>> 234 vdp->push_back(aGamma1);
>> 235
>> 236 G4double Phot2Energy =(1.-epsil)*TotalAvailableEnergy;
>> 237 G4double PositP= sqrt(PositKinEnergy*(PositKinEnergy+2.*electron_mass_c2));
>> 238 G4ThreeVector dir = PositDirection*PositP - Phot1Direction*Phot1Energy;
>> 239 G4ThreeVector Phot2Direction = dir.unit();
>> 240
>> 241 // create G4DynamicParticle object for the particle2
>> 242 G4DynamicParticle* aGamma2=
>> 243 new G4DynamicParticle (theGamma,Phot2Direction, Phot2Energy);
>> 244 vdp->push_back(aGamma2);
>> 245 /*
>> 246 G4cout << "Annihilation in fly: e0= " << PositKinEnergy
>> 247 << " m= " << electron_mass_c2
>> 248 << " e1= " << Phot1Energy
>> 249 << " e2= " << Phot2Energy << " dir= " << dir
>> 250 << " -> " << Phot1Direction << " "
>> 251 << Phot2Direction << G4endl;
>> 252 */
>> 253 }
>> 254 fParticleChange->SetProposedKineticEnergy(0.);
>> 255 fParticleChange->ProposeTrackStatus(fStopAndKill);
197 } 256 }
198 257
199 //....oooOO0OOooo........oooOO0OOooo........oo 258 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
200 259