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>> 27 // $Id: G4GammaConversionToMuons.cc 66996 2013-01-29 14:50:52Z gcosmo $
>> 28 //
27 // ------------ G4GammaConversionToMuo 29 // ------------ G4GammaConversionToMuons physics process ------
28 // by H.Burkhardt, S. Kelner and R. Ko 30 // by H.Burkhardt, S. Kelner and R. Kokoulin, April 2002
29 // 31 //
30 // 32 //
31 // 07-08-02: missprint in OR condition in DoIt 33 // 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 34 // 25-10-04: migrade to new interfaces of ParticleChange (vi)
33 // ------------------------------------------- 35 // ---------------------------------------------------------------------------
34 36
35 #include "G4GammaConversionToMuons.hh" 37 #include "G4GammaConversionToMuons.hh"
36 <<
37 #include "G4BetheHeitler5DModel.hh" <<
38 #include "G4Electron.hh" <<
39 #include "G4EmParameters.hh" <<
40 #include "G4EmProcessSubType.hh" <<
41 #include "G4Exp.hh" <<
42 #include "G4Gamma.hh" <<
43 #include "G4Log.hh" <<
44 #include "G4LossTableManager.hh" <<
45 #include "G4MuonMinus.hh" <<
46 #include "G4MuonPlus.hh" <<
47 #include "G4NistManager.hh" <<
48 #include "G4PhysicalConstants.hh" 38 #include "G4PhysicalConstants.hh"
49 #include "G4Positron.hh" <<
50 #include "G4ProductionCutsTable.hh" <<
51 #include "G4SystemOfUnits.hh" 39 #include "G4SystemOfUnits.hh"
52 #include "G4UnitsTable.hh" 40 #include "G4UnitsTable.hh"
>> 41 #include "G4MuonPlus.hh"
>> 42 #include "G4MuonMinus.hh"
53 43
54 //....oooOO0OOooo........oooOO0OOooo........oo 44 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
55 45
56 static const G4double sqrte = std::sqrt(std::e << 46 using namespace std;
57 static const G4double PowSat = -0.88; <<
58 47
59 G4GammaConversionToMuons::G4GammaConversionToM 48 G4GammaConversionToMuons::G4GammaConversionToMuons(const G4String& processName,
60 G4ProcessType type) << 49 G4ProcessType type):G4VDiscreteProcess (processName, type),
61 : G4VDiscreteProcess (processName, type), << 50 LowestEnergyLimit (4*G4MuonPlus::MuonPlus()->GetPDGMass()), // 4*Mmuon
62 Mmuon(G4MuonPlus::MuonPlus()->GetPDGMass() << 51 HighestEnergyLimit(1e21*eV), // ok to 1e21eV=1e12GeV, then LPM suppression
63 Rc(CLHEP::elm_coupling / Mmuon), << 52 CrossSecFactor(1.)
64 LimitEnergy(5. * Mmuon), << 53 {
65 LowestEnergyLimit(2. * Mmuon), << 54 SetProcessSubType(15);
66 HighestEnergyLimit(1e12 * CLHEP::GeV), // << 55 MeanFreePath = DBL_MAX;
67 theGamma(G4Gamma::Gamma()), <<
68 theMuonPlus(G4MuonPlus::MuonPlus()), <<
69 theMuonMinus(G4MuonMinus::MuonMinus()) <<
70 { <<
71 SetProcessSubType(fGammaConversionToMuMu); <<
72 fManager = G4LossTableManager::Instance(); <<
73 fManager->Register(this); <<
74 } 56 }
75 57
76 //....oooOO0OOooo........oooOO0OOooo........oo 58 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
77 59
78 G4GammaConversionToMuons::~G4GammaConversionTo << 60 // destructor
79 { << 61
80 fManager->DeRegister(this); << 62 G4GammaConversionToMuons::~G4GammaConversionToMuons() // (empty) destructor
81 } << 63 { }
82 64
83 //....oooOO0OOooo........oooOO0OOooo........oo 65 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
84 66
85 G4bool G4GammaConversionToMuons::IsApplicable( << 67 G4bool G4GammaConversionToMuons::IsApplicable(
>> 68 const G4ParticleDefinition& particle)
86 { 69 {
87 return (&part == theGamma); << 70 return ( &particle == G4Gamma::Gamma() );
88 } 71 }
89 72
90 //....oooOO0OOooo........oooOO0OOooo........oo 73 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
91 74
92 void G4GammaConversionToMuons::BuildPhysicsTab << 75 void G4GammaConversionToMuons::BuildPhysicsTable(const G4ParticleDefinition&)
93 { << 76 // Build cross section and mean free path tables
94 Energy5DLimit = G4EmParameters::Instance()-> << 77 { //here no tables, just calling PrintInfoDefinition
95 << 78 PrintInfoDefinition();
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(); <<
106 f5Dmodel->SetLeptonPair(theMuonPlus, theMu <<
107 const std::size_t numElems = G4ProductionC <<
108 const G4DataVector cuts(numElems); <<
109 f5Dmodel->Initialise(&p, cuts); <<
110 } <<
111 PrintInfoDefinition(); <<
112 } 79 }
113 80
114 //....oooOO0OOooo........oooOO0OOooo........oo 81 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
115 82
116 G4double G4GammaConversionToMuons::GetMeanFree << 83 G4double G4GammaConversionToMuons::GetMeanFreePath(const G4Track& aTrack,
117 << 84 G4double, G4ForceCondition*)
>> 85
118 // returns the photon mean free path in GEANT4 86 // returns the photon mean free path in GEANT4 internal units
>> 87 // (MeanFreePath is a private member of the class)
>> 88
119 { 89 {
120 const G4DynamicParticle* aDynamicGamma = aTr << 90 const G4DynamicParticle* aDynamicGamma = aTrack.GetDynamicParticle();
121 G4double GammaEnergy = aDynamicGamma->GetKin << 91 G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
122 const G4Material* aMaterial = aTrack.GetMate << 92 G4Material* aMaterial = aTrack.GetMaterial();
123 return ComputeMeanFreePath(GammaEnergy, aMat << 93
>> 94 if (GammaEnergy < LowestEnergyLimit)
>> 95 MeanFreePath = DBL_MAX;
>> 96 else
>> 97 MeanFreePath = ComputeMeanFreePath(GammaEnergy,aMaterial);
>> 98
>> 99 return MeanFreePath;
124 } 100 }
125 101
126 //....oooOO0OOooo........oooOO0OOooo........oo 102 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
127 103
128 G4double << 104 G4double G4GammaConversionToMuons::ComputeMeanFreePath(G4double GammaEnergy,
129 G4GammaConversionToMuons::ComputeMeanFreePath( << 105 G4Material* aMaterial)
130 <<
131 106
132 // computes and returns the photon mean free p 107 // computes and returns the photon mean free path in GEANT4 internal units
133 { 108 {
134 if(GammaEnergy <= LowestEnergyLimit) { retur <<
135 const G4ElementVector* theElementVector = aM 109 const G4ElementVector* theElementVector = aMaterial->GetElementVector();
136 const G4double* NbOfAtomsPerVolume = aMateri 110 const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();
137 111
138 G4double SIGMA = 0.0; << 112 G4double SIGMA = 0 ;
139 G4double fact = 1.0; <<
140 G4double e = GammaEnergy; <<
141 // low energy approximation as in Bethe-Heit <<
142 if(e < LimitEnergy) { <<
143 G4double y = (e - LowestEnergyLimit)/(Limi <<
144 fact = y*y; <<
145 e = LimitEnergy; <<
146 } <<
147 113
148 for ( std::size_t i=0 ; i < aMaterial->GetNu << 114 for ( size_t i=0 ; i < aMaterial->GetNumberOfElements() ; i++ )
149 { 115 {
150 SIGMA += NbOfAtomsPerVolume[i] * fact * << 116 G4double AtomicZ = (*theElementVector)[i]->GetZ();
151 ComputeCrossSectionPerAtom(e, (*theEleme << 117 G4double AtomicA = (*theElementVector)[i]->GetA()/(g/mole);
>> 118 SIGMA += NbOfAtomsPerVolume[i] *
>> 119 ComputeCrossSectionPerAtom(GammaEnergy,AtomicZ,AtomicA);
152 } 120 }
153 return (SIGMA > 0.0) ? 1./SIGMA : DBL_MAX; << 121 return SIGMA > DBL_MIN ? 1./SIGMA : DBL_MAX;
154 } 122 }
155 123
156 //....oooOO0OOooo........oooOO0OOooo........oo 124 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
157 125
158 G4double G4GammaConversionToMuons::GetCrossSec 126 G4double G4GammaConversionToMuons::GetCrossSectionPerAtom(
159 const G4Dyn 127 const G4DynamicParticle* aDynamicGamma,
160 const G4Ele << 128 G4Element* anElement)
161 129
162 // gives the total cross section per atom in G 130 // gives the total cross section per atom in GEANT4 internal units
163 { 131 {
164 return ComputeCrossSectionPerAtom(aDynamicG << 132 G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
165 anElement << 133 G4double AtomicZ = anElement->GetZ();
>> 134 G4double AtomicA = anElement->GetA()/(g/mole);
>> 135 G4double crossSection =
>> 136 ComputeCrossSectionPerAtom(GammaEnergy,AtomicZ,AtomicA);
>> 137 return crossSection;
166 } 138 }
167 139
168 //....oooOO0OOooo........oooOO0OOooo........oo 140 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
169 141
170 G4double G4GammaConversionToMuons::ComputeCros 142 G4double G4GammaConversionToMuons::ComputeCrossSectionPerAtom(
171 G4double Egam, G4int << 143 G4double Egam, G4double Z, G4double A)
172 144
173 // Calculates the microscopic cross section in 145 // Calculates the microscopic cross section in GEANT4 internal units.
174 // Total cross section parametrisation from H. 146 // Total cross section parametrisation from H.Burkhardt
175 // It gives a good description at any energy ( 147 // It gives a good description at any energy (from 0 to 10**21 eV)
176 { << 148 { static const G4double Mmuon=G4MuonPlus::MuonPlus()->GetPDGMass();
177 if(Egam <= LowestEnergyLimit) { return 0.0; << 149 static const G4double Mele=electron_mass_c2;
178 << 150 static const G4double Rc=elm_coupling/Mmuon; // classical particle radius
179 G4NistManager* nist = G4NistManager::Instanc << 151 static const G4double sqrte=sqrt(exp(1.));
>> 152 static const G4double PowSat=-0.88;
180 153
181 G4double PowThres, Ecor, B, Dn, Zthird, Winf << 154 static G4double CrossSection = 0.0 ;
182 155
183 if (Z == 1) { // special case of Hydrogen << 156 if ( A < 1. ) return 0;
184 B = 202.4; << 157 if ( Egam < 4*Mmuon ) return 0 ; // below threshold return 0
185 Dn = 1.49; <<
186 } <<
187 else { <<
188 B = 183.; <<
189 Dn = 1.54 * nist->GetA27(Z); <<
190 } <<
191 Zthird = 1. / nist->GetZ13(Z); // Z**(-1/3) <<
192 Winfty = B * Zthird * Mmuon / (Dn * electron <<
193 WMedAppr = 1. / (4. * Dn * sqrte * Mmuon); <<
194 Wsatur = Winfty / WMedAppr; <<
195 sigfac = 4. * fine_structure_const * Z * Z * <<
196 PowThres = 1.479 + 0.00799 * Dn; <<
197 Ecor = -18. + 4347. / (B * Zthird); <<
198 <<
199 G4double CorFuc = 1. + .04 * G4Log(1. + Ecor <<
200 G4double Eg = <<
201 G4Exp(G4Log(1. - 4. * Mmuon / Egam) * PowT <<
202 * G4Exp(G4Log(G4Exp(G4Log(Wsatur) * PowSat <<
203 158
204 G4double CrossSection = 7. / 9. * sigfac * G << 159 static G4double EgamLast=0,Zlast=0,PowThres,Ecor,B,Dn,Zthird,Winfty,WMedAppr,
205 CrossSection *= CrossSecFactor; // increase << 160 Wsatur,sigfac;
>> 161
>> 162 if(Zlast==Z && Egam==EgamLast) return CrossSection; // already calculated
>> 163 EgamLast=Egam;
>> 164
>> 165 if(Zlast!=Z) // new element
>> 166 { Zlast=Z;
>> 167 if(Z==1) // special case of Hydrogen
>> 168 { B=202.4;
>> 169 Dn=1.49;
>> 170 }
>> 171 else
>> 172 { B=183.;
>> 173 Dn=1.54*pow(A,0.27);
>> 174 }
>> 175 Zthird=pow(Z,-1./3.); // Z**(-1/3)
>> 176 Winfty=B*Zthird*Mmuon/(Dn*Mele);
>> 177 WMedAppr=1./(4.*Dn*sqrte*Mmuon);
>> 178 Wsatur=Winfty/WMedAppr;
>> 179 sigfac=4.*fine_structure_const*Z*Z*Rc*Rc;
>> 180 PowThres=1.479+0.00799*Dn;
>> 181 Ecor=-18.+4347./(B*Zthird);
>> 182 }
>> 183 G4double CorFuc=1.+.04*log(1.+Ecor/Egam);
>> 184 G4double Eg=pow(1.-4.*Mmuon/Egam,PowThres)*pow( pow(Wsatur,PowSat)+
>> 185 pow(Egam,PowSat),1./PowSat); // threshold and saturation
>> 186 CrossSection=7./9.*sigfac*log(1.+WMedAppr*CorFuc*Eg);
>> 187 CrossSection*=CrossSecFactor; // increase the CrossSection by (by default 1)
206 return CrossSection; 188 return CrossSection;
207 } 189 }
208 190
209 //....oooOO0OOooo........oooOO0OOooo........oo 191 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
210 192
211 void G4GammaConversionToMuons::SetCrossSecFact 193 void G4GammaConversionToMuons::SetCrossSecFactor(G4double fac)
212 // Set the factor to artificially increase the 194 // Set the factor to artificially increase the cross section
213 { << 195 { CrossSecFactor=fac;
214 if (fac < 0.0) return; << 196 G4cout << "The cross section for GammaConversionToMuons is artificially "
215 CrossSecFactor = fac; << 197 << "increased by the CrossSecFactor=" << CrossSecFactor << G4endl;
216 if (verboseLevel > 1) { <<
217 G4cout << "The cross section for GammaConv <<
218 << "increased by the CrossSecFactor <<
219 } <<
220 } 198 }
221 199
222 //....oooOO0OOooo........oooOO0OOooo........oo 200 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
223 201
224 G4VParticleChange* G4GammaConversionToMuons::P 202 G4VParticleChange* G4GammaConversionToMuons::PostStepDoIt(
225 203 const G4Track& aTrack,
226 204 const G4Step& aStep)
227 // 205 //
228 // generation of gamma->mu+mu- 206 // generation of gamma->mu+mu-
229 // 207 //
230 { 208 {
231 aParticleChange.Initialize(aTrack); 209 aParticleChange.Initialize(aTrack);
232 const G4Material* aMaterial = aTrack.GetMate << 210 G4Material* aMaterial = aTrack.GetMaterial();
>> 211
>> 212 static const G4double Mmuon=G4MuonPlus::MuonPlus()->GetPDGMass();
>> 213 static const G4double Mele=electron_mass_c2;
>> 214 static const G4double sqrte=sqrt(exp(1.));
233 215
234 // current Gamma energy and direction, retur 216 // current Gamma energy and direction, return if energy too low
235 const G4DynamicParticle* aDynamicGamma = aTr << 217 const G4DynamicParticle *aDynamicGamma = aTrack.GetDynamicParticle();
236 G4double Egam = aDynamicGamma->GetKineticEne 218 G4double Egam = aDynamicGamma->GetKineticEnergy();
237 if (Egam <= LowestEnergyLimit) { << 219 if (Egam < 4*Mmuon) return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
238 return G4VDiscreteProcess::PostStepDoIt(aT <<
239 } <<
240 // <<
241 // Kill the incident photon <<
242 // <<
243 aParticleChange.ProposeMomentumDirection( 0. <<
244 aParticleChange.ProposeEnergy( 0. ) ; <<
245 aParticleChange.ProposeTrackStatus( fStopAnd <<
246 <<
247 if (Egam <= Energy5DLimit) { <<
248 std::vector<G4DynamicParticle*> fvect; <<
249 f5Dmodel->SampleSecondaries(&fvect, aTrack <<
250 aTrack.GetDynamicParticle(), 0.0, DBL_ <<
251 for(auto dp : fvect) { aParticleChange.Add <<
252 return G4VDiscreteProcess::PostStepDoIt(aT <<
253 } <<
254 <<
255 G4ParticleMomentum GammaDirection = aDynamic 220 G4ParticleMomentum GammaDirection = aDynamicGamma->GetMomentumDirection();
256 221
257 // select randomly one element constituting 222 // select randomly one element constituting the material
258 const G4Element* anElement = SelectRandomAto << 223 const G4Element& anElement = *SelectRandomAtom(aDynamicGamma, aMaterial);
259 G4int Z = anElement->GetZasInt(); << 224 G4double Z = anElement.GetZ();
260 G4NistManager* nist = G4NistManager::Instanc << 225 G4double A = anElement.GetA()/(g/mole);
261 << 226
262 G4double B, Dn; << 227 static G4double Zlast=0,B,Dn,Zthird,Winfty,A027,C1Num2,C2Term2;
263 G4double A027 = nist->GetA27(Z); << 228 if(Zlast!=Z) // the element has changed
264 << 229 { Zlast=Z;
265 if (Z == 1) { // special case of Hydrogen << 230 if(Z==1) // special case of Hydrogen
266 B = 202.4; << 231 { B=202.4;
267 Dn = 1.49; << 232 Dn=1.49;
268 } << 233 }
269 else { << 234 else
270 B = 183.; << 235 { B=183.;
271 Dn = 1.54 * A027; << 236 Dn=1.54*pow(A,0.27);
>> 237 }
>> 238 Zthird=pow(Z,-1./3.); // Z**(-1/3)
>> 239 Winfty=B*Zthird*Mmuon/(Dn*Mele);
>> 240 A027=pow(A,0.27);
>> 241 G4double C1Num=0.35*A027;
>> 242 C1Num2=C1Num*C1Num;
>> 243 C2Term2=Mele/(183.*Zthird*Mmuon);
272 } 244 }
273 G4double Zthird = 1. / nist->GetZ13(Z); // <<
274 G4double Winfty = B * Zthird * Mmuon / (Dn * <<
275 <<
276 G4double C1Num = 0.138 * A027; <<
277 G4double C1Num2 = C1Num * C1Num; <<
278 G4double C2Term2 = electron_mass_c2 / (183. <<
279 245
280 G4double GammaMuonInv = Mmuon / Egam; << 246 G4double GammaMuonInv=Mmuon/Egam;
>> 247 G4double sqrtx=sqrt(.25-GammaMuonInv);
>> 248 G4double xmax=.5+sqrtx;
>> 249 G4double xmin=.5-sqrtx;
281 250
282 // generate xPlus according to the different 251 // generate xPlus according to the differential cross section by rejection
283 G4double xmin = (Egam <= LimitEnergy) ? 0.5 << 252 G4double Ds2=(Dn*sqrte-2.);
284 G4double xmax = 1. - xmin; << 253 G4double sBZ=sqrte*B*Zthird/Mele;
285 << 254 G4double LogWmaxInv=1./log(Winfty*(1.+2.*Ds2*GammaMuonInv)
286 G4double Ds2 = (Dn * sqrte - 2.); << 255 /(1.+2.*sBZ*Mmuon*GammaMuonInv));
287 G4double sBZ = sqrte * B * Zthird / electron << 256 G4double xPlus,xMinus,xPM,result,W;
288 G4double LogWmaxInv = << 257 do
289 1. / G4Log(Winfty * (1. + 2. * Ds2 * Gamma << 258 { xPlus=xmin+G4UniformRand()*(xmax-xmin);
290 G4double xPlus = 0.5; << 259 xMinus=1.-xPlus;
291 G4double xMinus = 0.5; << 260 xPM=xPlus*xMinus;
292 G4double xPM = 0.25; << 261 G4double del=Mmuon*Mmuon/(2.*Egam*xPM);
293 << 262 W=Winfty*(1.+Ds2*del/Mmuon)/(1.+sBZ*del);
294 G4int nn = 0; << 263 if(W<1.) W=1.; // to avoid negative cross section at xmin
295 const G4int nmax = 1000; << 264 G4double xxp=1.-4./3.*xPM; // the main xPlus dependence
296 << 265 result=xxp*log(W)*LogWmaxInv;
297 // sampling for Egam > LimitEnergy << 266 if(result>1.) {
298 if (xmin < 0.5) { << 267 G4cout << "G4GammaConversionToMuons::PostStepDoIt WARNING:"
299 G4double result, W; << 268 << " in dSigxPlusGen, result=" << result << " > 1" << G4endl;
300 do { <<
301 xPlus = xmin + G4UniformRand() * (xmax - <<
302 xMinus = 1. - xPlus; <<
303 xPM = xPlus * xMinus; <<
304 G4double del = Mmuon * Mmuon / (2. * Ega <<
305 W = Winfty * (1. + Ds2 * del / Mmuon) / <<
306 G4double xxp = 1. - 4. / 3. * xPM; // t <<
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 } 269 }
315 // Loop checking, 07-Aug-2015, Vladimir Iv <<
316 while (G4UniformRand() > result); <<
317 } 270 }
>> 271 while (G4UniformRand() > result);
318 272
319 // now generate the angular variables via th 273 // now generate the angular variables via the auxilary variables t,psi,rho
320 G4double t; 274 G4double t;
321 G4double psi; 275 G4double psi;
322 G4double rho; 276 G4double rho;
323 277
324 G4double a3 = (GammaMuonInv / (2. * xPM)); <<
325 G4double a33 = a3 * a3; <<
326 G4double f1; <<
327 G4double b1 = 1./(4.*C1Num2); <<
328 G4double b3 = b1*b1*b1; <<
329 G4double a21 = a33 + b1; <<
330 <<
331 G4double f1_max=-(1.-xPM)*(2.*b1+(a21+a33)*G <<
332 <<
333 G4double thetaPlus,thetaMinus,phiHalf; // fi 278 G4double thetaPlus,thetaMinus,phiHalf; // final angular variables
334 nn = 0; << 279
335 // t, psi, rho generation start (while angl << 280 do // t, psi, rho generation start (while angle < pi)
336 do { << 281 {
337 //generate t by the rejection method 282 //generate t by the rejection method
338 do { << 283 G4double C1=C1Num2* GammaMuonInv/xPM;
339 ++nn; << 284 G4double f1_max=(1.-xPM) / (1.+C1);
340 t=G4UniformRand(); << 285 G4double f1; // the probability density
341 G4double a34=a33/(t*t); << 286 do
342 G4double a22 = a34 + b1; << 287 { t=G4UniformRand();
343 if(std::abs(b1)<0.0001*a34) { << 288 f1=(1.-2.*xPM+4.*xPM*t*(1.-t)) / (1.+C1/(t*t));
344 // special case of a34=a22 because of << 289 if(f1<0 || f1> f1_max) // should never happend
345 f1=(1.-2.*xPM+4.*xPM*t*(1.-t))/(12.*a3 << 290 {
346 } << 291 G4cout << "G4GammaConversionToMuons::PostStepDoIt WARNING:"
347 else { << 292 << "outside allowed range f1=" << f1 << " is set to zero"
348 f1=-(1.-2.*xPM+4.*xPM*t*(1.-t))*(2.*b1 << 293 << G4endl;
349 } << 294 f1 = 0.0;
350 if (f1 < 0.0 || f1 > f1_max) { // shoul << 295 }
351 G4cout << "G4GammaConversionToMuons::P << 296 }
352 << "outside allowed range f1=" << f1 << 297 while ( G4UniformRand()*f1_max > f1);
353 << " is set to zero, a34 = "<< a34 << <<
354 << G4endl; <<
355 f1 = 0.0; <<
356 } <<
357 if(nn > nmax) { break; } <<
358 // Loop checking, 07-Aug-2015, Vladimir <<
359 } while ( G4UniformRand()*f1_max > f1); <<
360 // generate psi by the rejection method 298 // generate psi by the rejection method
361 G4double f2_max=1.-2.*xPM*(1.-4.*t*(1.-t)) 299 G4double f2_max=1.-2.*xPM*(1.-4.*t*(1.-t));
>> 300
362 // long version 301 // long version
363 G4double f2; 302 G4double f2;
364 do { << 303 do
365 ++nn; << 304 { psi=2.*pi*G4UniformRand();
366 psi=twopi*G4UniformRand(); << 305 f2=1.-2.*xPM+4.*xPM*t*(1.-t)*(1.+cos(2.*psi));
367 f2=1.-2.*xPM+4.*xPM*t*(1.-t)*(1.+std::co << 306 if(f2<0 || f2> f2_max) // should never happend
368 if(f2<0 || f2> f2_max) { // should never << 307 {
369 G4cout << "G4GammaConversionToMuons::P << 308 G4cout << "G4GammaConversionToMuons::PostStepDoIt WARNING:"
370 << "outside allowed range f2=" << 309 << "outside allowed range f2=" << f2 << " is set to zero"
371 f2 = 0.0; << 310 << G4endl;
372 } << 311 f2 = 0.0;
373 if(nn >= nmax) { break; } << 312 }
374 // Loop checking, 07-Aug-2015, Vladimir << 313 }
375 } while ( G4UniformRand()*f2_max > f2); << 314 while ( G4UniformRand()*f2_max > f2);
376 315
377 // generate rho by direct transformation 316 // generate rho by direct transformation
378 G4double C2Term1=GammaMuonInv/(2.*xPM*t); 317 G4double C2Term1=GammaMuonInv/(2.*xPM*t);
379 G4double C22 = C2Term1*C2Term1+C2Term2*C2T << 318 G4double C2=4./sqrt(xPM)*pow(C2Term1*C2Term1+C2Term2*C2Term2,2.);
380 G4double C2=4.*C22*C22/std::sqrt(xPM); << 319 G4double rhomax=1.9/A027*(1./t-1.);
381 G4double rhomax=(1./t-1.)*1.9/A027; << 320 G4double beta=log( (C2+pow(rhomax,4.))/C2 );
382 G4double beta=G4Log( (C2+rhomax*rhomax*rho << 321 rho=pow(C2 *( exp(beta*G4UniformRand())-1. ) ,0.25);
383 rho=G4Exp(G4Log(C2 *( G4Exp(beta*G4Uniform <<
384 322
385 //now get from t and psi the kinematical v 323 //now get from t and psi the kinematical variables
386 G4double u=std::sqrt(1./t-1.); << 324 G4double u=sqrt(1./t-1.);
387 G4double xiHalf=0.5*rho*std::cos(psi); << 325 G4double xiHalf=0.5*rho*cos(psi);
388 phiHalf=0.5*rho/u*std::sin(psi); << 326 phiHalf=0.5*rho/u*sin(psi);
389 327
390 thetaPlus =GammaMuonInv*(u+xiHalf)/xPlus; 328 thetaPlus =GammaMuonInv*(u+xiHalf)/xPlus;
391 thetaMinus=GammaMuonInv*(u-xiHalf)/xMinus; 329 thetaMinus=GammaMuonInv*(u-xiHalf)/xMinus;
392 330
393 // protection against infinite loop <<
394 if(nn > nmax) { <<
395 if(std::abs(thetaPlus)>pi) { thetaPlus = <<
396 if(std::abs(thetaMinus)>pi) { thetaMinus <<
397 } <<
398 <<
399 // Loop checking, 07-Aug-2015, Vladimir Iv <<
400 } while ( std::abs(thetaPlus)>pi || std::abs 331 } while ( std::abs(thetaPlus)>pi || std::abs(thetaMinus) >pi);
401 332
402 // now construct the vectors 333 // now construct the vectors
403 // azimuthal symmetry, take phi0 at random b 334 // azimuthal symmetry, take phi0 at random between 0 and 2 pi
404 G4double phi0=twopi*G4UniformRand(); << 335 G4double phi0=2.*pi*G4UniformRand();
405 G4double EPlus=xPlus*Egam; 336 G4double EPlus=xPlus*Egam;
406 G4double EMinus=xMinus*Egam; 337 G4double EMinus=xMinus*Egam;
407 338
408 // mu+ mu- directions for gamma in z-directi 339 // mu+ mu- directions for gamma in z-direction
409 G4ThreeVector MuPlusDirection ( std::sin(th << 340 G4ThreeVector MuPlusDirection ( sin(thetaPlus) *cos(phi0+phiHalf),
410 std::sin(thetaPlus) *std:: << 341 sin(thetaPlus) *sin(phi0+phiHalf), cos(thetaPlus) );
411 G4ThreeVector MuMinusDirection (-std::sin(th << 342 G4ThreeVector MuMinusDirection (-sin(thetaMinus)*cos(phi0-phiHalf),
412 -std::sin(thetaMinus) *std:: << 343 -sin(thetaMinus) *sin(phi0-phiHalf), cos(thetaMinus) );
413 // rotate to actual gamma direction 344 // rotate to actual gamma direction
414 MuPlusDirection.rotateUz(GammaDirection); 345 MuPlusDirection.rotateUz(GammaDirection);
415 MuMinusDirection.rotateUz(GammaDirection); 346 MuMinusDirection.rotateUz(GammaDirection);
416 << 347 aParticleChange.SetNumberOfSecondaries(2);
417 // create G4DynamicParticle object for the p 348 // create G4DynamicParticle object for the particle1
418 auto aParticle1 = new G4DynamicParticle(theM << 349 G4DynamicParticle* aParticle1= new G4DynamicParticle(
>> 350 G4MuonPlus::MuonPlus(),MuPlusDirection,EPlus-Mmuon);
419 aParticleChange.AddSecondary(aParticle1); 351 aParticleChange.AddSecondary(aParticle1);
420 // create G4DynamicParticle object for the p 352 // create G4DynamicParticle object for the particle2
421 auto aParticle2 = new G4DynamicParticle(theM << 353 G4DynamicParticle* aParticle2= new G4DynamicParticle(
>> 354 G4MuonMinus::MuonMinus(),MuMinusDirection,EMinus-Mmuon);
422 aParticleChange.AddSecondary(aParticle2); 355 aParticleChange.AddSecondary(aParticle2);
>> 356 //
>> 357 // Kill the incident photon
>> 358 //
>> 359 aParticleChange.ProposeMomentumDirection( 0., 0., 0. ) ;
>> 360 aParticleChange.ProposeEnergy( 0. ) ;
>> 361 aParticleChange.ProposeTrackStatus( fStopAndKill ) ;
423 // Reset NbOfInteractionLengthLeft and retu 362 // Reset NbOfInteractionLengthLeft and return aParticleChange
424 return G4VDiscreteProcess::PostStepDoIt( aTr 363 return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep );
425 } 364 }
426 365
427 //....oooOO0OOooo........oooOO0OOooo........oo 366 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
428 367
429 const G4Element* G4GammaConversionToMuons::Sel << 368 G4Element* G4GammaConversionToMuons::SelectRandomAtom(
430 const G4DynamicParticle* aDynamicGamma, << 369 const G4DynamicParticle* aDynamicGamma,
431 const G4Material* aMaterial) << 370 G4Material* aMaterial)
432 { 371 {
433 // select randomly 1 element within the mate 372 // select randomly 1 element within the material, invoked by PostStepDoIt
434 373
435 const std::size_t NumberOfElements = aM << 374 const G4int NumberOfElements = aMaterial->GetNumberOfElements();
436 const G4ElementVector* theElementVector = aM 375 const G4ElementVector* theElementVector = aMaterial->GetElementVector();
437 const G4Element* elm = (*theElementVector)[0 << 376 if (NumberOfElements == 1) return (*theElementVector)[0];
438 377
439 if (NumberOfElements > 1) { << 378 const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();
440 G4double e = std::max(aDynamicGamma->GetKi << 379
441 const G4double* natom = aMaterial->GetVecN << 380 G4double PartialSumSigma = 0. ;
442 << 381 G4double rval = G4UniformRand()/MeanFreePath;
443 G4double sum = 0.; << 382
444 for (std::size_t i=0; i<NumberOfElements; << 383
445 elm = (*theElementVector)[i]; << 384 for ( G4int i=0 ; i < NumberOfElements ; i++ )
446 sum += natom[i]*ComputeCrossSectionPerAt << 385 { PartialSumSigma += NbOfAtomsPerVolume[i] *
447 temp[i] = sum; << 386 GetCrossSectionPerAtom(aDynamicGamma, (*theElementVector)[i]);
448 } << 387 if (rval <= PartialSumSigma) return ((*theElementVector)[i]);
449 sum *= G4UniformRand(); <<
450 for (std::size_t i=0; i<NumberOfElements; <<
451 if(sum <= temp[i]) { <<
452 elm = (*theElementVector)[i]; <<
453 break; <<
454 } 388 }
455 } << 389 G4cout << " WARNING !!! - The Material '"<< aMaterial->GetName()
456 } << 390 << "' has no elements, NULL pointer returned." << G4endl;
457 return elm; << 391 return NULL;
458 } 392 }
459 393
460 //....oooOO0OOooo........oooOO0OOooo........oo 394 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
461 395
462 void G4GammaConversionToMuons::PrintInfoDefini 396 void G4GammaConversionToMuons::PrintInfoDefinition()
463 { 397 {
464 G4String comments = "gamma->mu+mu- Bethe Hei << 398 G4String comments ="gamma->mu+mu- Bethe Heitler process, SubType= ";
465 G4cout << G4endl << GetProcessName() << ": << 399 G4cout << G4endl << GetProcessName() << ": " << comments
>> 400 << GetProcessSubType() << G4endl;
466 G4cout << " good cross section parame 401 G4cout << " good cross section parametrization from "
467 << G4BestUnit(LowestEnergyLimit, "Ene << 402 << G4BestUnit(LowestEnergyLimit,"Energy")
468 << " GeV for all Z." << G4endl; << 403 << " to " << HighestEnergyLimit/GeV << " GeV for all Z." << G4endl;
469 G4cout << " cross section factor: " < <<
470 } 404 }
471 405
472 //....oooOO0OOooo........oooOO0OOooo........oo 406 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
473 407