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26 // 26 //
27 // ------------ G4GammaConversionToMuo 27 // ------------ G4GammaConversionToMuons physics process ------
28 // by H.Burkhardt, S. Kelner and R. Ko 28 // by H.Burkhardt, S. Kelner and R. Kokoulin, April 2002
29 // 29 //
30 // 30 //
31 // 07-08-02: missprint in OR condition in DoIt 31 // 07-08-02: missprint in OR condition in DoIt : f1<0 || f1>f1_max ..etc ...
32 // 25-10-04: migrade to new interfaces of Part 32 // 25-10-04: migrade to new interfaces of ParticleChange (vi)
33 // ------------------------------------------- 33 // ---------------------------------------------------------------------------
34 34
35 #include "G4GammaConversionToMuons.hh" 35 #include "G4GammaConversionToMuons.hh"
36 << 36 #include "G4PhysicalConstants.hh"
37 #include "G4BetheHeitler5DModel.hh" << 37 #include "G4SystemOfUnits.hh"
38 #include "G4Electron.hh" << 38 #include "G4UnitsTable.hh"
39 #include "G4EmParameters.hh" << 39 #include "G4MuonPlus.hh"
>> 40 #include "G4MuonMinus.hh"
40 #include "G4EmProcessSubType.hh" 41 #include "G4EmProcessSubType.hh"
41 #include "G4Exp.hh" << 42 #include "G4EmParameters.hh"
42 #include "G4Gamma.hh" <<
43 #include "G4Log.hh" <<
44 #include "G4LossTableManager.hh" 43 #include "G4LossTableManager.hh"
45 #include "G4MuonMinus.hh" << 44 #include "G4BetheHeitler5DModel.hh"
46 #include "G4MuonPlus.hh" << 45 #include "G4Gamma.hh"
47 #include "G4NistManager.hh" << 46 #include "G4Electron.hh"
48 #include "G4PhysicalConstants.hh" <<
49 #include "G4Positron.hh" 47 #include "G4Positron.hh"
>> 48 #include "G4NistManager.hh"
>> 49 #include "G4Log.hh"
>> 50 #include "G4Exp.hh"
50 #include "G4ProductionCutsTable.hh" 51 #include "G4ProductionCutsTable.hh"
51 #include "G4SystemOfUnits.hh" <<
52 #include "G4UnitsTable.hh" <<
53 52
54 //....oooOO0OOooo........oooOO0OOooo........oo 53 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
55 54
56 static const G4double sqrte = std::sqrt(std::e << 55 using namespace std;
57 static const G4double PowSat = -0.88; << 56
>> 57 static const G4double sqrte=sqrt(exp(1.));
>> 58 static const G4double PowSat=-0.88;
58 59
59 G4GammaConversionToMuons::G4GammaConversionToM 60 G4GammaConversionToMuons::G4GammaConversionToMuons(const G4String& processName,
60 G4ProcessType type) 61 G4ProcessType type)
61 : G4VDiscreteProcess (processName, type), 62 : G4VDiscreteProcess (processName, type),
62 Mmuon(G4MuonPlus::MuonPlus()->GetPDGMass() 63 Mmuon(G4MuonPlus::MuonPlus()->GetPDGMass()),
63 Rc(CLHEP::elm_coupling / Mmuon), << 64 Rc(CLHEP::elm_coupling/Mmuon),
64 LimitEnergy(5. * Mmuon), << 65 LimitEnergy (5.*Mmuon),
65 LowestEnergyLimit(2. * Mmuon), << 66 LowestEnergyLimit (2.*Mmuon),
66 HighestEnergyLimit(1e12 * CLHEP::GeV), // << 67 HighestEnergyLimit(1e12*CLHEP::GeV), // ok to 1e12GeV, then LPM suppression
67 theGamma(G4Gamma::Gamma()), 68 theGamma(G4Gamma::Gamma()),
68 theMuonPlus(G4MuonPlus::MuonPlus()), 69 theMuonPlus(G4MuonPlus::MuonPlus()),
69 theMuonMinus(G4MuonMinus::MuonMinus()) 70 theMuonMinus(G4MuonMinus::MuonMinus())
70 { << 71 {
71 SetProcessSubType(fGammaConversionToMuMu); 72 SetProcessSubType(fGammaConversionToMuMu);
72 fManager = G4LossTableManager::Instance(); 73 fManager = G4LossTableManager::Instance();
73 fManager->Register(this); 74 fManager->Register(this);
74 } 75 }
75 76
76 //....oooOO0OOooo........oooOO0OOooo........oo 77 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
77 78
78 G4GammaConversionToMuons::~G4GammaConversionTo << 79 G4GammaConversionToMuons::~G4GammaConversionToMuons()
79 { 80 {
80 fManager->DeRegister(this); 81 fManager->DeRegister(this);
81 } 82 }
82 83
83 //....oooOO0OOooo........oooOO0OOooo........oo 84 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
84 85
85 G4bool G4GammaConversionToMuons::IsApplicable( 86 G4bool G4GammaConversionToMuons::IsApplicable(const G4ParticleDefinition& part)
86 { 87 {
87 return (&part == theGamma); 88 return (&part == theGamma);
88 } 89 }
89 90
90 //....oooOO0OOooo........oooOO0OOooo........oo 91 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
91 92
92 void G4GammaConversionToMuons::BuildPhysicsTab 93 void G4GammaConversionToMuons::BuildPhysicsTable(const G4ParticleDefinition& p)
93 { << 94 // Build cross section and mean free path tables
>> 95 { //here no tables, just calling PrintInfoDefinition
94 Energy5DLimit = G4EmParameters::Instance()-> 96 Energy5DLimit = G4EmParameters::Instance()->MaxEnergyFor5DMuPair();
95 << 97 if(Energy5DLimit > 0.0 && nullptr != f5Dmodel) {
96 auto table = G4Material::GetMaterialTable(); <<
97 std::size_t nelm = 0; <<
98 for (auto const& mat : *table) { <<
99 std::size_t n = mat->GetNumberOfElements() <<
100 nelm = std::max(nelm, n); <<
101 } <<
102 temp.resize(nelm, 0); <<
103 <<
104 if (Energy5DLimit > 0.0 && nullptr != f5Dmod <<
105 f5Dmodel = new G4BetheHeitler5DModel(); 98 f5Dmodel = new G4BetheHeitler5DModel();
106 f5Dmodel->SetLeptonPair(theMuonPlus, theMu 99 f5Dmodel->SetLeptonPair(theMuonPlus, theMuonMinus);
107 const std::size_t numElems = G4ProductionC << 100 const size_t numElems = G4ProductionCutsTable::GetProductionCutsTable()->GetTableSize();
108 const G4DataVector cuts(numElems); 101 const G4DataVector cuts(numElems);
109 f5Dmodel->Initialise(&p, cuts); 102 f5Dmodel->Initialise(&p, cuts);
110 } 103 }
111 PrintInfoDefinition(); 104 PrintInfoDefinition();
112 } 105 }
113 106
114 //....oooOO0OOooo........oooOO0OOooo........oo 107 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
115 108
116 G4double G4GammaConversionToMuons::GetMeanFree << 109 G4double G4GammaConversionToMuons::GetMeanFreePath(const G4Track& aTrack,
117 << 110 G4double, G4ForceCondition*)
>> 111
118 // returns the photon mean free path in GEANT4 112 // returns the photon mean free path in GEANT4 internal units
>> 113 // (MeanFreePath is a private member of the class)
>> 114
119 { 115 {
120 const G4DynamicParticle* aDynamicGamma = aTr << 116 const G4DynamicParticle* aDynamicGamma = aTrack.GetDynamicParticle();
121 G4double GammaEnergy = aDynamicGamma->GetKin << 117 G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
122 const G4Material* aMaterial = aTrack.GetMate << 118 const G4Material* aMaterial = aTrack.GetMaterial();
123 return ComputeMeanFreePath(GammaEnergy, aMat << 119 return ComputeMeanFreePath(GammaEnergy, aMaterial);
124 } 120 }
125 121
126 //....oooOO0OOooo........oooOO0OOooo........oo 122 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
127 123
128 G4double 124 G4double
129 G4GammaConversionToMuons::ComputeMeanFreePath( 125 G4GammaConversionToMuons::ComputeMeanFreePath(G4double GammaEnergy,
130 126 const G4Material* aMaterial)
131 127
132 // computes and returns the photon mean free p 128 // computes and returns the photon mean free path in GEANT4 internal units
133 { 129 {
134 if(GammaEnergy <= LowestEnergyLimit) { retur 130 if(GammaEnergy <= LowestEnergyLimit) { return DBL_MAX; }
135 const G4ElementVector* theElementVector = aM 131 const G4ElementVector* theElementVector = aMaterial->GetElementVector();
136 const G4double* NbOfAtomsPerVolume = aMateri 132 const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();
137 133
138 G4double SIGMA = 0.0; 134 G4double SIGMA = 0.0;
139 G4double fact = 1.0; 135 G4double fact = 1.0;
140 G4double e = GammaEnergy; 136 G4double e = GammaEnergy;
141 // low energy approximation as in Bethe-Heit 137 // low energy approximation as in Bethe-Heitler model
142 if(e < LimitEnergy) { 138 if(e < LimitEnergy) {
143 G4double y = (e - LowestEnergyLimit)/(Limi 139 G4double y = (e - LowestEnergyLimit)/(LimitEnergy - LowestEnergyLimit);
144 fact = y*y; 140 fact = y*y;
145 e = LimitEnergy; 141 e = LimitEnergy;
146 } 142 }
147 143
148 for ( std::size_t i=0 ; i < aMaterial->GetNu << 144 for ( size_t i=0 ; i < aMaterial->GetNumberOfElements(); ++i)
149 { 145 {
150 SIGMA += NbOfAtomsPerVolume[i] * fact * 146 SIGMA += NbOfAtomsPerVolume[i] * fact *
151 ComputeCrossSectionPerAtom(e, (*theEleme 147 ComputeCrossSectionPerAtom(e, (*theElementVector)[i]->GetZasInt());
152 } 148 }
153 return (SIGMA > 0.0) ? 1./SIGMA : DBL_MAX; 149 return (SIGMA > 0.0) ? 1./SIGMA : DBL_MAX;
154 } 150 }
155 151
156 //....oooOO0OOooo........oooOO0OOooo........oo 152 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
157 153
158 G4double G4GammaConversionToMuons::GetCrossSec 154 G4double G4GammaConversionToMuons::GetCrossSectionPerAtom(
159 const G4Dyn 155 const G4DynamicParticle* aDynamicGamma,
160 const G4Ele 156 const G4Element* anElement)
161 157
162 // gives the total cross section per atom in G 158 // gives the total cross section per atom in GEANT4 internal units
163 { 159 {
164 return ComputeCrossSectionPerAtom(aDynamicG 160 return ComputeCrossSectionPerAtom(aDynamicGamma->GetKineticEnergy(),
165 anElement 161 anElement->GetZasInt());
166 } 162 }
167 163
168 //....oooOO0OOooo........oooOO0OOooo........oo 164 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
169 165
170 G4double G4GammaConversionToMuons::ComputeCros 166 G4double G4GammaConversionToMuons::ComputeCrossSectionPerAtom(
171 G4double Egam, G4int 167 G4double Egam, G4int Z)
172 168
173 // Calculates the microscopic cross section in 169 // Calculates the microscopic cross section in GEANT4 internal units.
174 // Total cross section parametrisation from H. 170 // Total cross section parametrisation from H.Burkhardt
175 // It gives a good description at any energy ( 171 // It gives a good description at any energy (from 0 to 10**21 eV)
176 { 172 {
177 if(Egam <= LowestEnergyLimit) { return 0.0; 173 if(Egam <= LowestEnergyLimit) { return 0.0; }
178 174
179 G4NistManager* nist = G4NistManager::Instanc 175 G4NistManager* nist = G4NistManager::Instance();
180 176
181 G4double PowThres, Ecor, B, Dn, Zthird, Winf << 177 G4double PowThres,Ecor,B,Dn,Zthird,Winfty,WMedAppr,
182 << 178 Wsatur,sigfac;
183 if (Z == 1) { // special case of Hydrogen << 179
184 B = 202.4; << 180 if(Z==1) // special case of Hydrogen
185 Dn = 1.49; << 181 { B=202.4;
186 } << 182 Dn=1.49;
187 else { << 183 }
188 B = 183.; << 184 else
189 Dn = 1.54 * nist->GetA27(Z); << 185 { B=183.;
190 } << 186 Dn=1.54*nist->GetA27(Z);
191 Zthird = 1. / nist->GetZ13(Z); // Z**(-1/3) << 187 }
192 Winfty = B * Zthird * Mmuon / (Dn * electron << 188 Zthird=1./nist->GetZ13(Z); // Z**(-1/3)
193 WMedAppr = 1. / (4. * Dn * sqrte * Mmuon); << 189 Winfty=B*Zthird*Mmuon/(Dn*electron_mass_c2);
194 Wsatur = Winfty / WMedAppr; << 190 WMedAppr=1./(4.*Dn*sqrte*Mmuon);
195 sigfac = 4. * fine_structure_const * Z * Z * << 191 Wsatur=Winfty/WMedAppr;
196 PowThres = 1.479 + 0.00799 * Dn; << 192 sigfac=4.*fine_structure_const*Z*Z*Rc*Rc;
197 Ecor = -18. + 4347. / (B * Zthird); << 193 PowThres=1.479+0.00799*Dn;
198 << 194 Ecor=-18.+4347./(B*Zthird);
199 G4double CorFuc = 1. + .04 * G4Log(1. + Ecor << 195
200 G4double Eg = << 196 G4double CorFuc=1.+.04*G4Log(1.+Ecor/Egam);
201 G4Exp(G4Log(1. - 4. * Mmuon / Egam) * PowT << 197 //G4double Eg=pow(1.-4.*Mmuon/Egam,PowThres)*pow( pow(Wsatur,PowSat)+
202 * G4Exp(G4Log(G4Exp(G4Log(Wsatur) * PowSat << 198 // pow(Egam,PowSat),1./PowSat); // threshold and saturation
203 << 199 G4double Eg=G4Exp(G4Log(1.-4.*Mmuon/Egam)*PowThres)*
204 G4double CrossSection = 7. / 9. * sigfac * G << 200 G4Exp(G4Log( G4Exp(G4Log(Wsatur)*PowSat)+G4Exp(G4Log(Egam)*PowSat))/PowSat);
205 CrossSection *= CrossSecFactor; // increase << 201 G4double CrossSection=7./9.*sigfac*G4Log(1.+WMedAppr*CorFuc*Eg);
>> 202 CrossSection *= CrossSecFactor; // increase the CrossSection by (by default 1)
206 return CrossSection; 203 return CrossSection;
207 } 204 }
208 205
209 //....oooOO0OOooo........oooOO0OOooo........oo 206 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
210 207
211 void G4GammaConversionToMuons::SetCrossSecFact 208 void G4GammaConversionToMuons::SetCrossSecFactor(G4double fac)
212 // Set the factor to artificially increase the 209 // Set the factor to artificially increase the cross section
213 { << 210 {
214 if (fac < 0.0) return; << 211 if(fac < 0.0) return;
215 CrossSecFactor = fac; << 212 CrossSecFactor=fac;
216 if (verboseLevel > 1) { << 213 G4cout << "The cross section for GammaConversionToMuons is artificially "
217 G4cout << "The cross section for GammaConv << 214 << "increased by the CrossSecFactor=" << CrossSecFactor << G4endl;
218 << "increased by the CrossSecFactor <<
219 } <<
220 } 215 }
221 216
222 //....oooOO0OOooo........oooOO0OOooo........oo 217 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
223 218
224 G4VParticleChange* G4GammaConversionToMuons::P 219 G4VParticleChange* G4GammaConversionToMuons::PostStepDoIt(
225 220 const G4Track& aTrack,
226 221 const G4Step& aStep)
227 // 222 //
228 // generation of gamma->mu+mu- 223 // generation of gamma->mu+mu-
229 // 224 //
230 { 225 {
231 aParticleChange.Initialize(aTrack); 226 aParticleChange.Initialize(aTrack);
232 const G4Material* aMaterial = aTrack.GetMate 227 const G4Material* aMaterial = aTrack.GetMaterial();
233 228
234 // current Gamma energy and direction, retur 229 // current Gamma energy and direction, return if energy too low
235 const G4DynamicParticle* aDynamicGamma = aTr << 230 const G4DynamicParticle *aDynamicGamma = aTrack.GetDynamicParticle();
236 G4double Egam = aDynamicGamma->GetKineticEne 231 G4double Egam = aDynamicGamma->GetKineticEnergy();
237 if (Egam <= LowestEnergyLimit) { 232 if (Egam <= LowestEnergyLimit) {
238 return G4VDiscreteProcess::PostStepDoIt(aT 233 return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
239 } 234 }
240 // 235 //
241 // Kill the incident photon 236 // Kill the incident photon
242 // 237 //
243 aParticleChange.ProposeMomentumDirection( 0. 238 aParticleChange.ProposeMomentumDirection( 0., 0., 0. ) ;
244 aParticleChange.ProposeEnergy( 0. ) ; 239 aParticleChange.ProposeEnergy( 0. ) ;
245 aParticleChange.ProposeTrackStatus( fStopAnd 240 aParticleChange.ProposeTrackStatus( fStopAndKill ) ;
246 241
247 if (Egam <= Energy5DLimit) { 242 if (Egam <= Energy5DLimit) {
248 std::vector<G4DynamicParticle*> fvect; 243 std::vector<G4DynamicParticle*> fvect;
249 f5Dmodel->SampleSecondaries(&fvect, aTrack 244 f5Dmodel->SampleSecondaries(&fvect, aTrack.GetMaterialCutsCouple(),
250 aTrack.GetDynamicParticle(), 0.0, DBL_ 245 aTrack.GetDynamicParticle(), 0.0, DBL_MAX);
>> 246 aParticleChange.SetNumberOfSecondaries(fvect.size());
251 for(auto dp : fvect) { aParticleChange.Add 247 for(auto dp : fvect) { aParticleChange.AddSecondary(dp); }
252 return G4VDiscreteProcess::PostStepDoIt(aT 248 return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
253 } 249 }
254 250
255 G4ParticleMomentum GammaDirection = aDynamic 251 G4ParticleMomentum GammaDirection = aDynamicGamma->GetMomentumDirection();
256 252
257 // select randomly one element constituting 253 // select randomly one element constituting the material
258 const G4Element* anElement = SelectRandomAto 254 const G4Element* anElement = SelectRandomAtom(aDynamicGamma, aMaterial);
259 G4int Z = anElement->GetZasInt(); 255 G4int Z = anElement->GetZasInt();
260 G4NistManager* nist = G4NistManager::Instanc 256 G4NistManager* nist = G4NistManager::Instance();
261 257
262 G4double B, Dn; << 258 G4double B,Dn;
263 G4double A027 = nist->GetA27(Z); 259 G4double A027 = nist->GetA27(Z);
264 260
265 if (Z == 1) { // special case of Hydrogen << 261 if(Z==1) // special case of Hydrogen
266 B = 202.4; << 262 { B=202.4;
267 Dn = 1.49; << 263 Dn=1.49;
268 } << 264 }
269 else { << 265 else
270 B = 183.; << 266 { B=183.;
271 Dn = 1.54 * A027; << 267 Dn=1.54*A027;
272 } << 268 }
273 G4double Zthird = 1. / nist->GetZ13(Z); // << 269 G4double Zthird=1./nist->GetZ13(Z); // Z**(-1/3)
274 G4double Winfty = B * Zthird * Mmuon / (Dn * << 270 G4double Winfty=B*Zthird*Mmuon/(Dn*electron_mass_c2);
275 271
276 G4double C1Num = 0.138 * A027; << 272 G4double C1Num=0.138*A027;
277 G4double C1Num2 = C1Num * C1Num; << 273 G4double C1Num2=C1Num*C1Num;
278 G4double C2Term2 = electron_mass_c2 / (183. << 274 G4double C2Term2=electron_mass_c2/(183.*Zthird*Mmuon);
279 275
280 G4double GammaMuonInv = Mmuon / Egam; << 276 G4double GammaMuonInv=Mmuon/Egam;
281 277
282 // generate xPlus according to the different 278 // generate xPlus according to the differential cross section by rejection
283 G4double xmin = (Egam <= LimitEnergy) ? 0.5 << 279 G4double xmin=(Egam < LimitEnergy) ? GammaMuonInv : .5-sqrt(.25-GammaMuonInv);
284 G4double xmax = 1. - xmin; << 280 G4double xmax=1.-xmin;
285 <<
286 G4double Ds2 = (Dn * sqrte - 2.); <<
287 G4double sBZ = sqrte * B * Zthird / electron <<
288 G4double LogWmaxInv = <<
289 1. / G4Log(Winfty * (1. + 2. * Ds2 * Gamma <<
290 G4double xPlus = 0.5; <<
291 G4double xMinus = 0.5; <<
292 G4double xPM = 0.25; <<
293 281
>> 282 G4double Ds2=(Dn*sqrte-2.);
>> 283 G4double sBZ=sqrte*B*Zthird/electron_mass_c2;
>> 284 G4double LogWmaxInv=1./G4Log(Winfty*(1.+2.*Ds2*GammaMuonInv)
>> 285 /(1.+2.*sBZ*Mmuon*GammaMuonInv));
>> 286 G4double xPlus,xMinus,xPM,result,W;
294 G4int nn = 0; 287 G4int nn = 0;
295 const G4int nmax = 1000; 288 const G4int nmax = 1000;
296 << 289 do {
297 // sampling for Egam > LimitEnergy << 290 xPlus=xmin+G4UniformRand()*(xmax-xmin);
298 if (xmin < 0.5) { << 291 xMinus=1.-xPlus;
299 G4double result, W; << 292 xPM=xPlus*xMinus;
300 do { << 293 G4double del=Mmuon*Mmuon/(2.*Egam*xPM);
301 xPlus = xmin + G4UniformRand() * (xmax - << 294 W=Winfty*(1.+Ds2*del/Mmuon)/(1.+sBZ*del);
302 xMinus = 1. - xPlus; << 295 G4double xxp=1.-4./3.*xPM; // the main xPlus dependence
303 xPM = xPlus * xMinus; << 296 result=(xxp > 0.) ? xxp*G4Log(W)*LogWmaxInv : 0.0;
304 G4double del = Mmuon * Mmuon / (2. * Ega << 297 if(result>1.) {
305 W = Winfty * (1. + Ds2 * del / Mmuon) / << 298 G4cout << "G4GammaConversionToMuons::PostStepDoIt WARNING:"
306 G4double xxp = 1. - 4. / 3. * xPM; // t << 299 << " in dSigxPlusGen, result=" << result << " > 1" << G4endl;
307 result = (xxp > 0.) ? xxp * G4Log(W) * L <<
308 if (result > 1.) { <<
309 G4cout << "G4GammaConversionToMuons::P <<
310 << " in dSigxPlusGen, result=" <<
311 } <<
312 ++nn; <<
313 if(nn >= nmax) { break; } <<
314 } 300 }
315 // Loop checking, 07-Aug-2015, Vladimir Iv << 301 ++nn;
316 while (G4UniformRand() > result); << 302 if(nn >= nmax) { break; }
317 } 303 }
>> 304 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
>> 305 while (G4UniformRand() > result);
318 306
319 // now generate the angular variables via th 307 // now generate the angular variables via the auxilary variables t,psi,rho
320 G4double t; 308 G4double t;
321 G4double psi; 309 G4double psi;
322 G4double rho; 310 G4double rho;
323 311
324 G4double a3 = (GammaMuonInv / (2. * xPM)); << 312 G4double a3 = (GammaMuonInv/(2.*xPM));
325 G4double a33 = a3 * a3; << 313 G4double a33 = a3*a3;
326 G4double f1; 314 G4double f1;
327 G4double b1 = 1./(4.*C1Num2); 315 G4double b1 = 1./(4.*C1Num2);
328 G4double b3 = b1*b1*b1; 316 G4double b3 = b1*b1*b1;
329 G4double a21 = a33 + b1; 317 G4double a21 = a33 + b1;
330 318
331 G4double f1_max=-(1.-xPM)*(2.*b1+(a21+a33)*G 319 G4double f1_max=-(1.-xPM)*(2.*b1+(a21+a33)*G4Log(a33/a21))/(2*b3);
332 320
333 G4double thetaPlus,thetaMinus,phiHalf; // fi 321 G4double thetaPlus,thetaMinus,phiHalf; // final angular variables
334 nn = 0; 322 nn = 0;
335 // t, psi, rho generation start (while angl 323 // t, psi, rho generation start (while angle < pi)
336 do { 324 do {
337 //generate t by the rejection method 325 //generate t by the rejection method
338 do { 326 do {
339 ++nn; 327 ++nn;
340 t=G4UniformRand(); 328 t=G4UniformRand();
341 G4double a34=a33/(t*t); 329 G4double a34=a33/(t*t);
342 G4double a22 = a34 + b1; 330 G4double a22 = a34 + b1;
343 if(std::abs(b1)<0.0001*a34) { << 331 if(std::abs(b1)<0.0001*a34)
344 // special case of a34=a22 because of << 332 // special case of a34=a22 because of logarithm accuracy
345 f1=(1.-2.*xPM+4.*xPM*t*(1.-t))/(12.*a3 << 333 {
346 } << 334 f1=(1.-2.*xPM+4.*xPM*t*(1.-t))/(12.*a34*a34*a34*a34);
347 else { << 335 }
348 f1=-(1.-2.*xPM+4.*xPM*t*(1.-t))*(2.*b1 << 336 else
349 } << 337 {
350 if (f1 < 0.0 || f1 > f1_max) { // shoul << 338 f1=-(1.-2.*xPM+4.*xPM*t*(1.-t))*(2.*b1+(a22+a34)*G4Log(a34/a22))/(2*b3);
351 G4cout << "G4GammaConversionToMuons::P << 339 }
352 << "outside allowed range f1=" << f1 << 340 if(f1<0.0 || f1> f1_max) // should never happend
353 << " is set to zero, a34 = "<< a34 << << 341 {
354 << G4endl; << 342 G4cout << "G4GammaConversionToMuons::PostStepDoIt WARNING:"
355 f1 = 0.0; << 343 << "outside allowed range f1=" << f1
356 } << 344 << " is set to zero, a34 = "<< a34 << " a22 = "<<a22<<"."
>> 345 << G4endl;
>> 346 f1 = 0.0;
>> 347 }
357 if(nn > nmax) { break; } 348 if(nn > nmax) { break; }
358 // Loop checking, 07-Aug-2015, Vladimir 349 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
359 } while ( G4UniformRand()*f1_max > f1); 350 } while ( G4UniformRand()*f1_max > f1);
360 // generate psi by the rejection method 351 // generate psi by the rejection method
361 G4double f2_max=1.-2.*xPM*(1.-4.*t*(1.-t)) 352 G4double f2_max=1.-2.*xPM*(1.-4.*t*(1.-t));
362 // long version 353 // long version
363 G4double f2; 354 G4double f2;
364 do { 355 do {
365 ++nn; 356 ++nn;
366 psi=twopi*G4UniformRand(); 357 psi=twopi*G4UniformRand();
367 f2=1.-2.*xPM+4.*xPM*t*(1.-t)*(1.+std::co << 358 f2=1.-2.*xPM+4.*xPM*t*(1.-t)*(1.+cos(2.*psi));
368 if(f2<0 || f2> f2_max) { // should never << 359 if(f2<0 || f2> f2_max) // should never happend
369 G4cout << "G4GammaConversionToMuons::P << 360 {
370 << "outside allowed range f2=" << 361 G4cout << "G4GammaConversionToMuons::PostStepDoIt WARNING:"
371 f2 = 0.0; << 362 << "outside allowed range f2=" << f2 << " is set to zero"
372 } << 363 << G4endl;
>> 364 f2 = 0.0;
>> 365 }
373 if(nn >= nmax) { break; } 366 if(nn >= nmax) { break; }
374 // Loop checking, 07-Aug-2015, Vladimir 367 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
375 } while ( G4UniformRand()*f2_max > f2); 368 } while ( G4UniformRand()*f2_max > f2);
376 369
377 // generate rho by direct transformation 370 // generate rho by direct transformation
378 G4double C2Term1=GammaMuonInv/(2.*xPM*t); 371 G4double C2Term1=GammaMuonInv/(2.*xPM*t);
379 G4double C22 = C2Term1*C2Term1+C2Term2*C2T 372 G4double C22 = C2Term1*C2Term1+C2Term2*C2Term2;
380 G4double C2=4.*C22*C22/std::sqrt(xPM); << 373 G4double C2=4.*C22*C22/sqrt(xPM);
381 G4double rhomax=(1./t-1.)*1.9/A027; 374 G4double rhomax=(1./t-1.)*1.9/A027;
382 G4double beta=G4Log( (C2+rhomax*rhomax*rho 375 G4double beta=G4Log( (C2+rhomax*rhomax*rhomax*rhomax)/C2 );
383 rho=G4Exp(G4Log(C2 *( G4Exp(beta*G4Uniform 376 rho=G4Exp(G4Log(C2 *( G4Exp(beta*G4UniformRand())-1. ))*0.25);
384 377
385 //now get from t and psi the kinematical v 378 //now get from t and psi the kinematical variables
386 G4double u=std::sqrt(1./t-1.); << 379 G4double u=sqrt(1./t-1.);
387 G4double xiHalf=0.5*rho*std::cos(psi); << 380 G4double xiHalf=0.5*rho*cos(psi);
388 phiHalf=0.5*rho/u*std::sin(psi); << 381 phiHalf=0.5*rho/u*sin(psi);
389 382
390 thetaPlus =GammaMuonInv*(u+xiHalf)/xPlus; 383 thetaPlus =GammaMuonInv*(u+xiHalf)/xPlus;
391 thetaMinus=GammaMuonInv*(u-xiHalf)/xMinus; 384 thetaMinus=GammaMuonInv*(u-xiHalf)/xMinus;
392 385
393 // protection against infinite loop 386 // protection against infinite loop
394 if(nn > nmax) { 387 if(nn > nmax) {
395 if(std::abs(thetaPlus)>pi) { thetaPlus = 388 if(std::abs(thetaPlus)>pi) { thetaPlus = 0.0; }
396 if(std::abs(thetaMinus)>pi) { thetaMinus 389 if(std::abs(thetaMinus)>pi) { thetaMinus = 0.0; }
397 } 390 }
398 391
399 // Loop checking, 07-Aug-2015, Vladimir Iv 392 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
400 } while ( std::abs(thetaPlus)>pi || std::abs 393 } while ( std::abs(thetaPlus)>pi || std::abs(thetaMinus) >pi);
401 394
402 // now construct the vectors 395 // now construct the vectors
403 // azimuthal symmetry, take phi0 at random b 396 // azimuthal symmetry, take phi0 at random between 0 and 2 pi
404 G4double phi0=twopi*G4UniformRand(); 397 G4double phi0=twopi*G4UniformRand();
405 G4double EPlus=xPlus*Egam; 398 G4double EPlus=xPlus*Egam;
406 G4double EMinus=xMinus*Egam; 399 G4double EMinus=xMinus*Egam;
407 400
408 // mu+ mu- directions for gamma in z-directi 401 // mu+ mu- directions for gamma in z-direction
409 G4ThreeVector MuPlusDirection ( std::sin(th << 402 G4ThreeVector MuPlusDirection ( sin(thetaPlus) *cos(phi0+phiHalf),
410 std::sin(thetaPlus) *std:: << 403 sin(thetaPlus) *sin(phi0+phiHalf), cos(thetaPlus) );
411 G4ThreeVector MuMinusDirection (-std::sin(th << 404 G4ThreeVector MuMinusDirection (-sin(thetaMinus)*cos(phi0-phiHalf),
412 -std::sin(thetaMinus) *std:: << 405 -sin(thetaMinus) *sin(phi0-phiHalf), cos(thetaMinus) );
413 // rotate to actual gamma direction 406 // rotate to actual gamma direction
414 MuPlusDirection.rotateUz(GammaDirection); 407 MuPlusDirection.rotateUz(GammaDirection);
415 MuMinusDirection.rotateUz(GammaDirection); 408 MuMinusDirection.rotateUz(GammaDirection);
416 << 409 aParticleChange.SetNumberOfSecondaries(2);
417 // create G4DynamicParticle object for the p 410 // create G4DynamicParticle object for the particle1
418 auto aParticle1 = new G4DynamicParticle(theM << 411 G4DynamicParticle* aParticle1 =
>> 412 new G4DynamicParticle(theMuonPlus,MuPlusDirection,EPlus-Mmuon);
419 aParticleChange.AddSecondary(aParticle1); 413 aParticleChange.AddSecondary(aParticle1);
420 // create G4DynamicParticle object for the p 414 // create G4DynamicParticle object for the particle2
421 auto aParticle2 = new G4DynamicParticle(theM << 415 G4DynamicParticle* aParticle2 =
>> 416 new G4DynamicParticle(theMuonMinus,MuMinusDirection,EMinus-Mmuon);
422 aParticleChange.AddSecondary(aParticle2); 417 aParticleChange.AddSecondary(aParticle2);
423 // Reset NbOfInteractionLengthLeft and retu 418 // Reset NbOfInteractionLengthLeft and return aParticleChange
424 return G4VDiscreteProcess::PostStepDoIt( aTr 419 return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep );
425 } 420 }
426 421
427 //....oooOO0OOooo........oooOO0OOooo........oo 422 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
428 423
429 const G4Element* G4GammaConversionToMuons::Sel 424 const G4Element* G4GammaConversionToMuons::SelectRandomAtom(
430 const G4DynamicParticle* aDynamicGamma, 425 const G4DynamicParticle* aDynamicGamma,
431 const G4Material* aMaterial) 426 const G4Material* aMaterial)
432 { 427 {
433 // select randomly 1 element within the mate 428 // select randomly 1 element within the material, invoked by PostStepDoIt
434 429
435 const std::size_t NumberOfElements = aM << 430 const G4int NumberOfElements = aMaterial->GetNumberOfElements();
436 const G4ElementVector* theElementVector = aM 431 const G4ElementVector* theElementVector = aMaterial->GetElementVector();
437 const G4Element* elm = (*theElementVector)[0 432 const G4Element* elm = (*theElementVector)[0];
438 433
439 if (NumberOfElements > 1) { << 434 if (NumberOfElements > 1) {
440 G4double e = std::max(aDynamicGamma->GetKi << 435 const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();
441 const G4double* natom = aMaterial->GetVecN << 436
>> 437 G4double PartialSumSigma = 0.;
>> 438 G4double rval = G4UniformRand()/MeanFreePath;
442 439
443 G4double sum = 0.; << 440 for (G4int i=0; i<NumberOfElements; ++i)
444 for (std::size_t i=0; i<NumberOfElements; << 441 {
445 elm = (*theElementVector)[i]; 442 elm = (*theElementVector)[i];
446 sum += natom[i]*ComputeCrossSectionPerAt << 443 PartialSumSigma += NbOfAtomsPerVolume[i]
447 temp[i] = sum; << 444 *GetCrossSectionPerAtom(aDynamicGamma, elm);
448 } << 445 if (rval <= PartialSumSigma) { break; }
449 sum *= G4UniformRand(); <<
450 for (std::size_t i=0; i<NumberOfElements; <<
451 if(sum <= temp[i]) { <<
452 elm = (*theElementVector)[i]; <<
453 break; <<
454 } <<
455 } 446 }
456 } 447 }
457 return elm; 448 return elm;
458 } 449 }
459 450
460 //....oooOO0OOooo........oooOO0OOooo........oo 451 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
461 452
462 void G4GammaConversionToMuons::PrintInfoDefini 453 void G4GammaConversionToMuons::PrintInfoDefinition()
463 { 454 {
464 G4String comments = "gamma->mu+mu- Bethe Hei << 455 G4String comments ="gamma->mu+mu- Bethe Heitler process, SubType= ";
465 G4cout << G4endl << GetProcessName() << ": << 456 G4cout << G4endl << GetProcessName() << ": " << comments
>> 457 << GetProcessSubType() << G4endl;
466 G4cout << " good cross section parame 458 G4cout << " good cross section parametrization from "
467 << G4BestUnit(LowestEnergyLimit, "Ene << 459 << G4BestUnit(LowestEnergyLimit,"Energy")
468 << " GeV for all Z." << G4endl; << 460 << " to " << HighestEnergyLimit/GeV << " GeV for all Z." << G4endl;
469 G4cout << " cross section factor: " < <<
470 } 461 }
471 462
472 //....oooOO0OOooo........oooOO0OOooo........oo 463 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
473 464