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27 // 27 //
28 // ------------ G4AnnihiToMuPair physi 28 // ------------ G4AnnihiToMuPair physics process ------
29 // by H.Burkhardt, S. Kelner and R. Ko 29 // by H.Burkhardt, S. Kelner and R. Kokoulin, November 2002
30 // ------------------------------------------- 30 // -----------------------------------------------------------------------------
31 // 31 //
32 //....oooOO0OOooo........oooOO0OOooo........oo 32 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......//
33 // 33 //
34 // 27.01.03 : first implementation (hbu) 34 // 27.01.03 : first implementation (hbu)
35 // 04.02.03 : cosmetic simplifications (mma) 35 // 04.02.03 : cosmetic simplifications (mma)
36 // 25.10.04 : migrade to new interfaces of Par 36 // 25.10.04 : migrade to new interfaces of ParticleChange (vi)
37 // 28.02.18 : cross section now including SSS 37 // 28.02.18 : cross section now including SSS threshold factor
38 // 38 //
39 //....oooOO0OOooo........oooOO0OOooo........oo 39 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
40 40
41 #include "G4AnnihiToMuPair.hh" 41 #include "G4AnnihiToMuPair.hh"
42 42
43 #include "G4Exp.hh" << 43 #include "G4ios.hh"
44 #include "G4LossTableManager.hh" << 44 #include "Randomize.hh"
45 #include "G4Material.hh" <<
46 #include "G4MuonMinus.hh" <<
47 #include "G4MuonPlus.hh" <<
48 #include "G4PhysicalConstants.hh" 45 #include "G4PhysicalConstants.hh"
>> 46 #include "G4SystemOfUnits.hh"
>> 47
49 #include "G4Positron.hh" 48 #include "G4Positron.hh"
>> 49 #include "G4MuonPlus.hh"
>> 50 #include "G4MuonMinus.hh"
>> 51 #include "G4Material.hh"
50 #include "G4Step.hh" 52 #include "G4Step.hh"
51 #include "G4SystemOfUnits.hh" << 53 #include "G4LossTableManager.hh"
52 #include "G4TauMinus.hh" <<
53 #include "G4TauPlus.hh" <<
54 #include "G4ios.hh" <<
55 #include "Randomize.hh" <<
56 54
57 //....oooOO0OOooo........oooOO0OOooo........oo 55 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
58 56
>> 57 using namespace std;
>> 58
59 G4AnnihiToMuPair::G4AnnihiToMuPair(const G4Str 59 G4AnnihiToMuPair::G4AnnihiToMuPair(const G4String& processName,
60 G4ProcessType type):G4VDiscreteProcess (pr 60 G4ProcessType type):G4VDiscreteProcess (processName, type)
61 { 61 {
62 //e+ Energy threshold 62 //e+ Energy threshold
63 if(processName == "AnnihiToTauPair") { << 63 const G4double Mu_massc2 = G4MuonPlus::MuonPlus()->GetPDGMass();
64 SetProcessSubType(fAnnihilationToTauTau); << 64 LowestEnergyLimit = 2.*Mu_massc2*Mu_massc2/electron_mass_c2 - electron_mass_c2;
65 part1 = G4TauPlus::TauPlus(); << 65
66 part2 = G4TauMinus::TauMinus(); << 66 //modele ok up to 1000 TeV due to neglected Z-interference
67 fInfo = "e+e->tau+tau-"; << 67 HighestEnergyLimit = 1000.*TeV;
68 } else { << 68
69 SetProcessSubType(fAnnihilationToMuMu); << 69 CurrentSigma = 0.0;
70 part1 = G4MuonPlus::MuonPlus(); << 70 CrossSecFactor = 1.;
71 part2 = G4MuonMinus::MuonMinus(); << 71 SetProcessSubType(6);
72 } << 72 G4LossTableManager::Instance()->Register(this);
73 fMass = part1->GetPDGMass(); <<
74 fLowEnergyLimit = 2. * fMass * fMass / CLHEP <<
75 <<
76 // model is ok up to 1000 TeV due to neglect <<
77 fHighEnergyLimit = 1000. * TeV; <<
78 <<
79 fCurrentSigma = 0.0; <<
80 fCrossSecFactor = 1.; <<
81 fManager = G4LossTableManager::Instance(); <<
82 fManager->Register(this); <<
83 } 73 }
84 74
85 //....oooOO0OOooo........oooOO0OOooo........oo 75 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
86 76
87 G4AnnihiToMuPair::~G4AnnihiToMuPair() // (empt 77 G4AnnihiToMuPair::~G4AnnihiToMuPair() // (empty) destructor
88 { 78 {
89 fManager->DeRegister(this); << 79 G4LossTableManager::Instance()->DeRegister(this);
90 } 80 }
91 81
92 //....oooOO0OOooo........oooOO0OOooo........oo 82 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
93 83
94 G4bool G4AnnihiToMuPair::IsApplicable(const G4 84 G4bool G4AnnihiToMuPair::IsApplicable(const G4ParticleDefinition& particle)
95 { 85 {
96 return ( &particle == G4Positron::Positron() 86 return ( &particle == G4Positron::Positron() );
97 } 87 }
98 88
99 //....oooOO0OOooo........oooOO0OOooo........oo 89 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
100 90
101 void G4AnnihiToMuPair::BuildPhysicsTable(const 91 void G4AnnihiToMuPair::BuildPhysicsTable(const G4ParticleDefinition&)
>> 92 // Build cross section and mean free path tables
>> 93 //here no tables, just calling PrintInfoDefinition
102 { 94 {
>> 95 CurrentSigma = 0.0;
103 PrintInfoDefinition(); 96 PrintInfoDefinition();
104 } 97 }
105 98
106 //....oooOO0OOooo........oooOO0OOooo........oo 99 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
107 100
108 void G4AnnihiToMuPair::SetCrossSecFactor(G4dou 101 void G4AnnihiToMuPair::SetCrossSecFactor(G4double fac)
109 // Set the factor to artificially increase the 102 // Set the factor to artificially increase the cross section
110 { 103 {
111 fCrossSecFactor = fac; << 104 CrossSecFactor = fac;
112 //G4cout << "The cross section for AnnihiToM << 105 G4cout << "The cross section for AnnihiToMuPair is artificially "
113 // << "increased by the CrossSecFactor << 106 << "increased by the CrossSecFactor=" << CrossSecFactor << G4endl;
114 } 107 }
115 108
116 //....oooOO0OOooo........oooOO0OOooo........oo 109 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
117 110
118 G4double G4AnnihiToMuPair::ComputeCrossSection << 111 G4double G4AnnihiToMuPair::ComputeCrossSectionPerAtom(G4double Epos, G4double Z)
119 // Calculates the microscopic cross section in 112 // Calculates the microscopic cross section in GEANT4 internal units.
120 // It gives a good description from threshold 113 // It gives a good description from threshold to 1000 GeV
121 { 114 {
122 G4double rmuon = CLHEP::elm_coupling/fMass; << 115 static const G4double Mmuon = G4MuonPlus::MuonPlus()->GetPDGMass();
123 G4double sig0 = CLHEP::pi*rmuon*rmuon/3.; << 116 static const G4double Rmuon = CLHEP::elm_coupling/Mmuon; //classical particle radius
124 const G4double pial = CLHEP::pi*CLHEP::fine_ << 117 static const G4double Sig0 = CLHEP::pi*Rmuon*Rmuon/3.; //constant in crossSection
>> 118 static const G4double pia = CLHEP::pi * CLHEP::fine_structure_const; // pi * alphaQED
125 119
126 if (e <= fLowEnergyLimit) return 0.0; << 120 G4double CrossSection = 0.;
>> 121 if (Epos < LowestEnergyLimit) return CrossSection;
127 122
128 const G4double xi = fLowEnergyLimit/e; << 123 G4double xi = LowestEnergyLimit/Epos;
129 const G4double piaxi = pial * std::sqrt(xi); << 124 G4double piaxi = pia * sqrt(xi);
130 G4double sigma = sig0 * xi * (1. + xi*0.5); << 125 G4double SigmaEl = Sig0 * xi * (1.+xi/2.) * piaxi;
131 //G4cout << "### xi= " << xi << " piaxi=" << << 126 if( Epos>LowestEnergyLimit+1.e-5 ) SigmaEl /= (1.-std::exp( -piaxi/std::sqrt(1-xi) ));
132 << 127 CrossSection = SigmaEl*Z; // SigmaEl per electron * number of electrons per atom
133 // argument of the exponent below 0.1 or abo << 128 return CrossSection;
134 // Sigma per electron * number of electrons <<
135 if(xi <= 1.0 - 100*piaxi*piaxi) { <<
136 sigma *= std::sqrt(1.0 - xi); <<
137 } <<
138 else if (xi >= 1.0 - 0.01 * piaxi * piaxi) { <<
139 sigma *= piaxi; <<
140 } <<
141 else { <<
142 sigma *= piaxi / (1. - G4Exp(-piaxi / std: <<
143 } <<
144 // G4cout << "### sigma= " << sigma << G4end <<
145 return sigma; <<
146 } 129 }
147 130
148 //....oooOO0OOooo........oooOO0OOooo........oo 131 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
149 132
150 G4double G4AnnihiToMuPair::ComputeCrossSection << 133 G4double G4AnnihiToMuPair::CrossSectionPerVolume(G4double PositronEnergy,
151 << 134 const G4Material* aMaterial)
152 { 135 {
153 return ComputeCrossSectionPerElectron(energy << 136 const G4ElementVector* theElementVector = aMaterial->GetElementVector();
154 } << 137 const G4double* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();
155 138
156 //....oooOO0OOooo........oooOO0OOooo........oo << 139 G4double SIGMA = 0.0;
157 140
158 G4double G4AnnihiToMuPair::CrossSectionPerVolu << 141 for ( size_t i=0 ; i < aMaterial->GetNumberOfElements() ; ++i )
159 const G4Material* aMaterial) << 142 {
160 { << 143 G4double AtomicZ = (*theElementVector)[i]->GetZ();
161 return ComputeCrossSectionPerElectron(energy << 144 SIGMA += NbOfAtomsPerVolume[i] *
>> 145 ComputeCrossSectionPerAtom(PositronEnergy,AtomicZ);
>> 146 }
>> 147 return SIGMA;
162 } 148 }
163 149
164 //....oooOO0OOooo........oooOO0OOooo........oo 150 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
165 151
166 G4double G4AnnihiToMuPair::GetMeanFreePath(con 152 G4double G4AnnihiToMuPair::GetMeanFreePath(const G4Track& aTrack,
167 G4d 153 G4double, G4ForceCondition*)
>> 154
168 // returns the positron mean free path in GEAN 155 // returns the positron mean free path in GEANT4 internal units
>> 156
169 { 157 {
170 const G4DynamicParticle* aDynamicPositron = 158 const G4DynamicParticle* aDynamicPositron = aTrack.GetDynamicParticle();
171 G4double energy = aDynamicPositron->GetTotal << 159 G4double PositronEnergy = aDynamicPositron->GetKineticEnergy()
172 const G4Material* aMaterial = aTrack.GetMate << 160 +electron_mass_c2;
173 << 161 G4Material* aMaterial = aTrack.GetMaterial();
174 // cross section before step << 162 CurrentSigma = CrossSectionPerVolume(PositronEnergy, aMaterial);
175 fCurrentSigma = CrossSectionPerVolume(energy <<
176 163
177 // increase the CrossSection by CrossSecFact 164 // increase the CrossSection by CrossSecFactor (default 1)
178 return (fCurrentSigma > 0.0) ? 1.0/(fCurrent << 165 G4double mfp = DBL_MAX;
>> 166 if(CurrentSigma > DBL_MIN) mfp = 1.0/(CurrentSigma*CrossSecFactor);
>> 167
>> 168 return mfp;
179 } 169 }
180 170
181 //....oooOO0OOooo........oooOO0OOooo........oo 171 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
182 172
183 G4VParticleChange* G4AnnihiToMuPair::PostStepD 173 G4VParticleChange* G4AnnihiToMuPair::PostStepDoIt(const G4Track& aTrack,
184 174 const G4Step& aStep)
185 // 175 //
186 // generation of e+e- -> mu+mu- 176 // generation of e+e- -> mu+mu-
187 // 177 //
188 { 178 {
>> 179
189 aParticleChange.Initialize(aTrack); 180 aParticleChange.Initialize(aTrack);
>> 181 static const G4double Mele=electron_mass_c2;
>> 182 static const G4double Mmuon=G4MuonPlus::MuonPlus()->GetPDGMass();
190 183
191 // current Positron energy and direction, re 184 // current Positron energy and direction, return if energy too low
192 const G4DynamicParticle *aDynamicPositron = 185 const G4DynamicParticle *aDynamicPositron = aTrack.GetDynamicParticle();
193 const G4double Mele = CLHEP::electron_mass_c << 186 G4double Epos = aDynamicPositron->GetKineticEnergy() + Mele;
194 G4double Epos = aDynamicPositron->GetTotalEn <<
195 G4double xs = CrossSectionPerVolume(Epos, aT <<
196 187
197 // test of cross section 188 // test of cross section
198 if(xs > 0.0 && fCurrentSigma*G4UniformRand() << 189 if(CurrentSigma*G4UniformRand() >
199 return G4VDiscreteProcess::PostStepDoIt(aT << 190 CrossSectionPerVolume(Epos, aTrack.GetMaterial()))
>> 191 {
>> 192 return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
>> 193 }
>> 194
>> 195 if (Epos < LowestEnergyLimit) {
>> 196 return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
200 } 197 }
201 198
202 const G4ThreeVector PosiDirection = aDynamic << 199 G4ParticleMomentum PositronDirection =
203 G4double xi = fLowEnergyLimit/Epos; // xi is << 200 aDynamicPositron->GetMomentumDirection();
204 // goes << 201 G4double xi = LowestEnergyLimit/Epos; // xi is always less than 1,
>> 202 // goes to 0 at high Epos
205 203
206 // generate cost; probability function 1+cos << 204 // generate cost
207 // 205 //
208 G4double cost; 206 G4double cost;
209 do { cost = 2.*G4UniformRand()-1.; } 207 do { cost = 2.*G4UniformRand()-1.; }
210 // Loop checking, 07-Aug-2015, Vladimir Ivan 208 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
211 while (2.*G4UniformRand() > 1.+xi+cost*cost* 209 while (2.*G4UniformRand() > 1.+xi+cost*cost*(1.-xi) );
212 G4double sint = std::sqrt(1.-cost*cost); << 210 //1+cost**2 at high Epos
>> 211 G4double sint = sqrt(1.-cost*cost);
213 212
214 // generate phi 213 // generate phi
215 // 214 //
216 G4double phi = 2.*CLHEP::pi*G4UniformRand(); << 215 G4double phi=2.*pi*G4UniformRand();
217 216
218 G4double Ecm = std::sqrt(0.5*Mele*(Epos+Me << 217 G4double Ecm = sqrt(0.5*Mele*(Epos+Mele));
219 G4double Pcm = std::sqrt(Ecm*Ecm - fMass*f << 218 G4double Pcm = sqrt(Ecm*Ecm-Mmuon*Mmuon);
220 G4double beta = std::sqrt((Epos-Mele)/(Epos << 219 G4double beta = sqrt((Epos-Mele)/(Epos+Mele));
221 G4double gamma = Ecm/Mele; << 220 G4double gamma = Ecm/Mele; // =sqrt((Epos+Mele)/(2.*Mele));
222 G4double Pt = Pcm*sint; 221 G4double Pt = Pcm*sint;
223 222
224 // energy and momentum of the muons in the L 223 // energy and momentum of the muons in the Lab
225 // 224 //
226 G4double EmuPlus = gamma*(Ecm + cost*beta* << 225 G4double EmuPlus = gamma*( Ecm+cost*beta*Pcm);
227 G4double EmuMinus = gamma*(Ecm - cost*beta* << 226 G4double EmuMinus = gamma*( Ecm-cost*beta*Pcm);
228 G4double PmuPlusZ = gamma*(beta*Ecm + cost* << 227 G4double PmuPlusZ = gamma*(beta*Ecm+cost* Pcm);
229 G4double PmuMinusZ = gamma*(beta*Ecm - cost* << 228 G4double PmuMinusZ = gamma*(beta*Ecm-cost* Pcm);
230 G4double PmuPlusX = Pt*std::cos(phi); << 229 G4double PmuPlusX = Pt*cos(phi);
231 G4double PmuPlusY = Pt*std::sin(phi); << 230 G4double PmuPlusY = Pt*sin(phi);
232 G4double PmuMinusX =-PmuPlusX; << 231 G4double PmuMinusX =-Pt*cos(phi);
233 G4double PmuMinusY =-PmuPlusY; << 232 G4double PmuMinusY =-Pt*sin(phi);
234 // absolute momenta 233 // absolute momenta
235 G4double PmuPlus = std::sqrt(Pt*Pt+PmuPlusZ << 234 G4double PmuPlus = sqrt(Pt*Pt+PmuPlusZ *PmuPlusZ );
236 G4double PmuMinus = std::sqrt(Pt*Pt+PmuMinus << 235 G4double PmuMinus = sqrt(Pt*Pt+PmuMinusZ*PmuMinusZ);
237 236
238 // mu+ mu- directions for Positron in z-dire 237 // mu+ mu- directions for Positron in z-direction
239 // 238 //
240 G4ThreeVector MuPlusDirection(PmuPlusX / Pmu << 239 G4ThreeVector
241 G4ThreeVector MuMinusDirection(PmuMinusX / P << 240 MuPlusDirection ( PmuPlusX/PmuPlus, PmuPlusY/PmuPlus, PmuPlusZ/PmuPlus );
>> 241 G4ThreeVector
>> 242 MuMinusDirection(PmuMinusX/PmuMinus,PmuMinusY/PmuMinus,PmuMinusZ/PmuMinus);
242 243
243 // rotate to actual Positron direction 244 // rotate to actual Positron direction
244 // 245 //
245 MuPlusDirection.rotateUz(PosiDirection); << 246 MuPlusDirection.rotateUz(PositronDirection);
246 MuMinusDirection.rotateUz(PosiDirection); << 247 MuMinusDirection.rotateUz(PositronDirection);
247 248
248 aParticleChange.SetNumberOfSecondaries(2); 249 aParticleChange.SetNumberOfSecondaries(2);
249 <<
250 // create G4DynamicParticle object for the p 250 // create G4DynamicParticle object for the particle1
251 auto aParticle1 = new G4DynamicParticle(part << 251 G4DynamicParticle* aParticle1= new G4DynamicParticle(
>> 252 G4MuonPlus::MuonPlus(),MuPlusDirection,EmuPlus-Mmuon);
252 aParticleChange.AddSecondary(aParticle1); 253 aParticleChange.AddSecondary(aParticle1);
253 // create G4DynamicParticle object for the p 254 // create G4DynamicParticle object for the particle2
254 auto aParticle2 = new G4DynamicParticle(part << 255 G4DynamicParticle* aParticle2= new G4DynamicParticle(
>> 256 G4MuonMinus::MuonMinus(),MuMinusDirection,EmuMinus-Mmuon);
255 aParticleChange.AddSecondary(aParticle2); 257 aParticleChange.AddSecondary(aParticle2);
256 258
257 // Kill the incident positron 259 // Kill the incident positron
258 // 260 //
259 aParticleChange.ProposeEnergy(0.); 261 aParticleChange.ProposeEnergy(0.);
260 aParticleChange.ProposeTrackStatus(fStopAndK 262 aParticleChange.ProposeTrackStatus(fStopAndKill);
261 263
262 return &aParticleChange; 264 return &aParticleChange;
263 } 265 }
264 266
265 //....oooOO0OOooo........oooOO0OOooo........oo 267 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
266 268
267 void G4AnnihiToMuPair::PrintInfoDefinition() 269 void G4AnnihiToMuPair::PrintInfoDefinition()
268 { 270 {
269 G4String comments = fInfo + " annihilation, << 271 G4String comments ="e+e->mu+mu- annihilation, atomic e- at rest, SubType=.";
270 G4cout << G4endl << GetProcessName() << ": << 272 G4cout << G4endl << GetProcessName() << ": " << comments
271 G4cout << " threshold at " << fLowEne << 273 << GetProcessSubType() << G4endl;
272 << " good description up to " << fHig << 274 G4cout << " threshold at " << LowestEnergyLimit/GeV << " GeV"
273 << G4endl; << 275 << " good description up to "
>> 276 << HighestEnergyLimit/TeV << " TeV for all Z." << G4endl;
274 } 277 }
275 278
276 //....oooOO0OOooo........oooOO0OOooo........oo 279 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
277 280