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26 // 26 //
27 // Author: D.H. Wright 27 // Author: D.H. Wright
28 // Date: 1 May 2012 28 // Date: 1 May 2012
29 // 29 //
30 // Description: model for electron and positro 30 // Description: model for electron and positron interaction with nuclei
31 // using the equivalent photon sp 31 // using the equivalent photon spectrum. A real gamma is
32 // produced from the virtual phot 32 // produced from the virtual photon spectrum and is then
33 // interacted hadronically by the 33 // interacted hadronically by the Bertini cascade at low
34 // energies. At high energies th 34 // energies. At high energies the gamma is treated as a
35 // pi0 and interacted with the nu 35 // pi0 and interacted with the nucleus using the FTFP model.
36 // The electro- and photo-nuclear 36 // The electro- and photo-nuclear cross sections of
37 // M. Kossov are used to generate 37 // M. Kossov are used to generate the virtual photon
38 // spectrum. 38 // spectrum.
39 // 39 //
40 40
41 #include "G4ElectroVDNuclearModel.hh" 41 #include "G4ElectroVDNuclearModel.hh"
42 42
43 #include "G4PhysicalConstants.hh" 43 #include "G4PhysicalConstants.hh"
44 #include "G4SystemOfUnits.hh" 44 #include "G4SystemOfUnits.hh"
45 45
46 #include "G4ElectroNuclearCrossSection.hh" 46 #include "G4ElectroNuclearCrossSection.hh"
47 #include "G4PhotoNuclearCrossSection.hh" 47 #include "G4PhotoNuclearCrossSection.hh"
48 #include "G4CrossSectionDataSetRegistry.hh" 48 #include "G4CrossSectionDataSetRegistry.hh"
49 49
50 #include "G4CascadeInterface.hh" 50 #include "G4CascadeInterface.hh"
51 #include "G4TheoFSGenerator.hh" 51 #include "G4TheoFSGenerator.hh"
52 #include "G4GeneratorPrecompoundInterface.hh" 52 #include "G4GeneratorPrecompoundInterface.hh"
53 #include "G4ExcitationHandler.hh" 53 #include "G4ExcitationHandler.hh"
54 #include "G4PreCompoundModel.hh" 54 #include "G4PreCompoundModel.hh"
55 #include "G4LundStringFragmentation.hh" 55 #include "G4LundStringFragmentation.hh"
56 #include "G4ExcitedStringDecay.hh" 56 #include "G4ExcitedStringDecay.hh"
57 #include "G4FTFModel.hh" 57 #include "G4FTFModel.hh"
58 58
59 #include "G4HadFinalState.hh" 59 #include "G4HadFinalState.hh"
60 #include "G4HadronicInteractionRegistry.hh" 60 #include "G4HadronicInteractionRegistry.hh"
61 #include "G4PhysicsModelCatalog.hh" <<
62 <<
63 #include "G4ElectroNuclearCrossSection.hh" <<
64 #include "G4PhotoNuclearCrossSection.hh" <<
65 #include "G4GammaNuclearXS.hh" <<
66 <<
67 61
68 G4ElectroVDNuclearModel::G4ElectroVDNuclearMod 62 G4ElectroVDNuclearModel::G4ElectroVDNuclearModel()
69 : G4HadronicInteraction("G4ElectroVDNuclearMo 63 : G4HadronicInteraction("G4ElectroVDNuclearModel"),
70 leptonKE(0.0), photonEnergy(0.0), photonQ2( << 64 leptonKE(0.0), photonEnergy(0.0), photonQ2(0.0)
71 { 65 {
72 SetMinEnergy(0.0); 66 SetMinEnergy(0.0);
73 SetMaxEnergy(1*PeV); 67 SetMaxEnergy(1*PeV);
74 <<
75 electroXS = 68 electroXS =
76 (G4ElectroNuclearCrossSection*)G4CrossSect 69 (G4ElectroNuclearCrossSection*)G4CrossSectionDataSetRegistry::Instance()->
77 GetCrossSectionDataSet(G4ElectroNuclearCro 70 GetCrossSectionDataSet(G4ElectroNuclearCrossSection::Default_Name());
78 if ( electroXS == nullptr ) { <<
79 electroXS = new G4ElectroNuclearCrossSecti <<
80 } <<
81 <<
82 gammaXS = 71 gammaXS =
83 (G4PhotoNuclearCrossSection*)G4CrossSectio 72 (G4PhotoNuclearCrossSection*)G4CrossSectionDataSetRegistry::Instance()->
84 GetCrossSectionDataSet(G4PhotoNuclearCross 73 GetCrossSectionDataSet(G4PhotoNuclearCrossSection::Default_Name());
85 if ( gammaXS == nullptr ) { <<
86 gammaXS = <<
87 (G4GammaNuclearXS*)G4CrossSectionDataSet <<
88 GetCrossSectionDataSet(G4GammaNuclearXS: <<
89 if ( gammaXS == nullptr ) { <<
90 gammaXS = new G4PhotoNuclearCrossSection <<
91 } <<
92 } <<
93 74
94 // reuse existing pre-compound model 75 // reuse existing pre-compound model
95 G4GeneratorPrecompoundInterface* precoInterf 76 G4GeneratorPrecompoundInterface* precoInterface
96 = new G4GeneratorPrecompoundInterface(); 77 = new G4GeneratorPrecompoundInterface();
97 G4HadronicInteraction* p = 78 G4HadronicInteraction* p =
98 G4HadronicInteractionRegistry::Instance()- 79 G4HadronicInteractionRegistry::Instance()->FindModel("PRECO");
99 G4VPreCompoundModel* pre = static_cast<G4VPr 80 G4VPreCompoundModel* pre = static_cast<G4VPreCompoundModel*>(p);
100 if(!pre) { pre = new G4PreCompoundModel(); } 81 if(!pre) { pre = new G4PreCompoundModel(); }
101 precoInterface->SetDeExcitation(pre); 82 precoInterface->SetDeExcitation(pre);
102 83
103 // string model 84 // string model
104 ftfp = new G4TheoFSGenerator(); 85 ftfp = new G4TheoFSGenerator();
105 ftfp->SetTransport(precoInterface); 86 ftfp->SetTransport(precoInterface);
106 theFragmentation = new G4LundStringFragmenta 87 theFragmentation = new G4LundStringFragmentation();
107 theStringDecay = new G4ExcitedStringDecay(th 88 theStringDecay = new G4ExcitedStringDecay(theFragmentation);
108 G4FTFModel* theStringModel = new G4FTFModel( 89 G4FTFModel* theStringModel = new G4FTFModel();
109 theStringModel->SetFragmentationModel(theStr 90 theStringModel->SetFragmentationModel(theStringDecay);
110 ftfp->SetHighEnergyGenerator(theStringModel) 91 ftfp->SetHighEnergyGenerator(theStringModel);
111 92
112 // Build Bertini model 93 // Build Bertini model
113 bert = new G4CascadeInterface(); 94 bert = new G4CascadeInterface();
114 <<
115 // Creator model ID <<
116 secID = G4PhysicsModelCatalog::GetModelID( " <<
117 } 95 }
118 96
119 G4ElectroVDNuclearModel::~G4ElectroVDNuclearMo 97 G4ElectroVDNuclearModel::~G4ElectroVDNuclearModel()
120 { 98 {
121 delete theFragmentation; 99 delete theFragmentation;
122 delete theStringDecay; 100 delete theStringDecay;
123 } 101 }
124 102
125 void G4ElectroVDNuclearModel::ModelDescription 103 void G4ElectroVDNuclearModel::ModelDescription(std::ostream& outFile) const
126 { 104 {
127 outFile << "G4ElectroVDNuclearModel handles 105 outFile << "G4ElectroVDNuclearModel handles the inelastic scattering\n"
128 << "of e- and e+ from nuclei using t 106 << "of e- and e+ from nuclei using the equivalent photon\n"
129 << "approximation in which the incom 107 << "approximation in which the incoming lepton generates a\n"
130 << "virtual photon at the electromag 108 << "virtual photon at the electromagnetic vertex, and the\n"
131 << "virtual photon is converted to a 109 << "virtual photon is converted to a real photon. At low\n"
132 << "energies, the photon interacts d 110 << "energies, the photon interacts directly with the nucleus\n"
133 << "using the Bertini cascade. At h 111 << "using the Bertini cascade. At high energies the photon\n"
134 << "is converted to a pi0 which inte 112 << "is converted to a pi0 which interacts using the FTFP\n"
135 << "model. The electro- and gamma-n 113 << "model. The electro- and gamma-nuclear cross sections of\n"
136 << "M. Kossov are used to generate t 114 << "M. Kossov are used to generate the virtual photon spectrum\n";
137 } 115 }
138 116
139 117
140 G4HadFinalState* 118 G4HadFinalState*
141 G4ElectroVDNuclearModel::ApplyYourself(const G 119 G4ElectroVDNuclearModel::ApplyYourself(const G4HadProjectile& aTrack,
142 G4Nucle 120 G4Nucleus& targetNucleus)
143 { 121 {
144 // Set up default particle change (just re 122 // Set up default particle change (just returns initial state)
145 theParticleChange.Clear(); 123 theParticleChange.Clear();
146 theParticleChange.SetStatusChange(isAlive) 124 theParticleChange.SetStatusChange(isAlive);
147 leptonKE = aTrack.GetKineticEnergy(); 125 leptonKE = aTrack.GetKineticEnergy();
148 theParticleChange.SetEnergyChange(leptonKE 126 theParticleChange.SetEnergyChange(leptonKE);
149 theParticleChange.SetMomentumChange(aTrack 127 theParticleChange.SetMomentumChange(aTrack.Get4Momentum().vect().unit() );
150 128
151 // Set up sanity checks for real photon pr 129 // Set up sanity checks for real photon production
152 G4DynamicParticle lepton(aTrack.GetDefinit 130 G4DynamicParticle lepton(aTrack.GetDefinition(), aTrack.Get4Momentum() );
153 131
154 // Need to call GetElementCrossSection bef 132 // Need to call GetElementCrossSection before calling GetEquivalentPhotonEnergy.
155 const G4Material* mat = aTrack.GetMaterial << 133 G4Material* mat = 0;
156 G4int targZ = targetNucleus.GetZ_asInt(); 134 G4int targZ = targetNucleus.GetZ_asInt();
157 electroXS->GetElementCrossSection(&lepton, 135 electroXS->GetElementCrossSection(&lepton, targZ, mat);
158 136
159 photonEnergy = electroXS->GetEquivalentPho 137 photonEnergy = electroXS->GetEquivalentPhotonEnergy();
160 // Photon energy cannot exceed lepton ener 138 // Photon energy cannot exceed lepton energy
161 if (photonEnergy < leptonKE) { 139 if (photonEnergy < leptonKE) {
162 photonQ2 = electroXS->GetEquivalentPho 140 photonQ2 = electroXS->GetEquivalentPhotonQ2(photonEnergy);
163 G4double dM = G4Proton::Proton()->GetP 141 G4double dM = G4Proton::Proton()->GetPDGMass() + G4Neutron::Neutron()->GetPDGMass();
164 // Photon 142 // Photon
165 if (photonEnergy > photonQ2/dM) { 143 if (photonEnergy > photonQ2/dM) {
166 // Produce recoil lepton and trans 144 // Produce recoil lepton and transferred photon
167 G4DynamicParticle* transferredPhot 145 G4DynamicParticle* transferredPhoton = CalculateEMVertex(aTrack, targetNucleus);
168 // Interact gamma with nucleus 146 // Interact gamma with nucleus
169 if (transferredPhoton) CalculateHa 147 if (transferredPhoton) CalculateHadronicVertex(transferredPhoton, targetNucleus);
170 } 148 }
171 } 149 }
172 return &theParticleChange; 150 return &theParticleChange;
173 } 151 }
174 152
175 153
176 G4DynamicParticle* 154 G4DynamicParticle*
177 G4ElectroVDNuclearModel::CalculateEMVertex(con 155 G4ElectroVDNuclearModel::CalculateEMVertex(const G4HadProjectile& aTrack,
178 G4N 156 G4Nucleus& targetNucleus)
179 { 157 {
180 G4DynamicParticle photon(G4Gamma::Gamma(), p 158 G4DynamicParticle photon(G4Gamma::Gamma(), photonEnergy,
181 G4ThreeVector(0.,0. 159 G4ThreeVector(0.,0.,1.) );
182 160
183 // Get gamma cross section at Q**2 = 0 (real 161 // Get gamma cross section at Q**2 = 0 (real gamma)
184 G4int targZ = targetNucleus.GetZ_asInt(); 162 G4int targZ = targetNucleus.GetZ_asInt();
185 const G4Material* mat = aTrack.GetMaterial() << 163 G4Material* mat = 0;
186 G4double sigNu = 164 G4double sigNu =
187 gammaXS->GetElementCrossSection(&photon, t 165 gammaXS->GetElementCrossSection(&photon, targZ, mat);
188 166
189 // Change real gamma energy to equivalent en 167 // Change real gamma energy to equivalent energy and get cross section at that energy
190 G4double dM = G4Proton::Proton()->GetPDGMass 168 G4double dM = G4Proton::Proton()->GetPDGMass() + G4Neutron::Neutron()->GetPDGMass();
191 photon.SetKineticEnergy(photonEnergy - photo 169 photon.SetKineticEnergy(photonEnergy - photonQ2/dM);
192 G4double sigK = 170 G4double sigK =
193 gammaXS->GetElementCrossSection(&photon, t 171 gammaXS->GetElementCrossSection(&photon, targZ, mat);
194 G4double rndFraction = electroXS->GetVirtual 172 G4double rndFraction = electroXS->GetVirtualFactor(photonEnergy, photonQ2);
195 173
196 // No gamma produced, return null ptr 174 // No gamma produced, return null ptr
197 if (sigNu*G4UniformRand() > sigK*rndFraction 175 if (sigNu*G4UniformRand() > sigK*rndFraction) return 0;
198 176
199 // Scatter the lepton 177 // Scatter the lepton
200 G4double mProj = aTrack.GetDefinition()->Get 178 G4double mProj = aTrack.GetDefinition()->GetPDGMass();
201 G4double mProj2 = mProj*mProj; 179 G4double mProj2 = mProj*mProj;
202 G4double iniE = leptonKE + mProj; 180 G4double iniE = leptonKE + mProj; // Total energy of incident lepton
203 G4double finE = iniE - photonEnergy; 181 G4double finE = iniE - photonEnergy; // Total energy of scattered lepton
204 theParticleChange.SetEnergyChange(finE-mProj 182 theParticleChange.SetEnergyChange(finE-mProj);
205 G4double iniP = std::sqrt(iniE*iniE-mProj2); 183 G4double iniP = std::sqrt(iniE*iniE-mProj2); // Incident lepton momentum
206 G4double finP = std::sqrt(finE*finE-mProj2); 184 G4double finP = std::sqrt(finE*finE-mProj2); // Scattered lepton momentum
207 G4double cost = (iniE*finE - mProj2 - photon 185 G4double cost = (iniE*finE - mProj2 - photonQ2/2.)/iniP/finP; // cos(theta) from Q**2
208 if (cost > 1.) cost= 1.; 186 if (cost > 1.) cost= 1.;
209 if (cost < -1.) cost=-1.; 187 if (cost < -1.) cost=-1.;
210 G4double sint = std::sqrt(1.-cost*cost); 188 G4double sint = std::sqrt(1.-cost*cost);
211 189
212 G4ThreeVector dir = aTrack.Get4Momentum().ve 190 G4ThreeVector dir = aTrack.Get4Momentum().vect().unit();
213 G4ThreeVector ortx = dir.orthogonal().unit() 191 G4ThreeVector ortx = dir.orthogonal().unit(); // Ortho-normal to scattering plane
214 G4ThreeVector orty = dir.cross(ortx); 192 G4ThreeVector orty = dir.cross(ortx); // Third unit vector
215 G4double phi = twopi*G4UniformRand(); 193 G4double phi = twopi*G4UniformRand();
216 G4double sinx = sint*std::sin(phi); 194 G4double sinx = sint*std::sin(phi);
217 G4double siny = sint*std::cos(phi); 195 G4double siny = sint*std::cos(phi);
218 G4ThreeVector findir = cost*dir+sinx*ortx+si 196 G4ThreeVector findir = cost*dir+sinx*ortx+siny*orty;
219 theParticleChange.SetMomentumChange(findir); 197 theParticleChange.SetMomentumChange(findir); // change lepton direction
220 198
221 // Create a gamma with momentum equal to mom 199 // Create a gamma with momentum equal to momentum transfer
222 G4ThreeVector photonMomentum = iniP*dir - fi 200 G4ThreeVector photonMomentum = iniP*dir - finP*findir;
223 G4DynamicParticle* gamma = new G4DynamicPart 201 G4DynamicParticle* gamma = new G4DynamicParticle(G4Gamma::Gamma(),
224 202 photonEnergy, photonMomentum);
225 return gamma; 203 return gamma;
226 } 204 }
227 205
228 206
229 void 207 void
230 G4ElectroVDNuclearModel::CalculateHadronicVert 208 G4ElectroVDNuclearModel::CalculateHadronicVertex(G4DynamicParticle* incident,
231 209 G4Nucleus& target)
232 { 210 {
233 G4HadFinalState* hfs = 0; 211 G4HadFinalState* hfs = 0;
234 G4double gammaE = incident->GetTotalEnergy() 212 G4double gammaE = incident->GetTotalEnergy();
235 213
236 if (gammaE < 10*GeV) { 214 if (gammaE < 10*GeV) {
237 G4HadProjectile projectile(*incident); 215 G4HadProjectile projectile(*incident);
238 hfs = bert->ApplyYourself(projectile, targ 216 hfs = bert->ApplyYourself(projectile, target);
239 } else { 217 } else {
240 // At high energies convert incident gamma 218 // At high energies convert incident gamma to a pion
241 G4double piMass = G4PionZero::PionZero()-> 219 G4double piMass = G4PionZero::PionZero()->GetPDGMass();
242 G4double piMom = std::sqrt(gammaE*gammaE - 220 G4double piMom = std::sqrt(gammaE*gammaE - piMass*piMass);
243 G4ThreeVector piMomentum(incident->GetMome 221 G4ThreeVector piMomentum(incident->GetMomentumDirection() );
244 piMomentum *= piMom; 222 piMomentum *= piMom;
245 G4DynamicParticle theHadron(G4PionZero::Pi 223 G4DynamicParticle theHadron(G4PionZero::PionZero(), piMomentum);
246 G4HadProjectile projectile(theHadron); 224 G4HadProjectile projectile(theHadron);
247 hfs = ftfp->ApplyYourself(projectile, targ 225 hfs = ftfp->ApplyYourself(projectile, target);
248 } 226 }
249 227
250 delete incident; 228 delete incident;
251 229
252 // Assign the creator model ID to the second <<
253 for ( size_t i = 0; i < hfs->GetNumberOfSeco <<
254 hfs->GetSecondary( i )->SetCreatorModelID( <<
255 } <<
256 <<
257 // Copy secondaries from sub-model to model 230 // Copy secondaries from sub-model to model
258 theParticleChange.AddSecondaries(hfs); 231 theParticleChange.AddSecondaries(hfs);
259 } 232 }
260 233
261 234