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1 // 1 2 // ******************************************* 3 // * License and Disclaimer 4 // * 5 // * The Geant4 software is copyright of th 6 // * the Geant4 Collaboration. It is provided 7 // * conditions of the Geant4 Software License 8 // * LICENSE and available at http://cern.ch/ 9 // * include a list of copyright holders. 10 // * 11 // * Neither the authors of this software syst 12 // * institutes,nor the agencies providing fin 13 // * work make any representation or warran 14 // * regarding this software system or assum 15 // * use. Please see the license in the file 16 // * for the full disclaimer and the limitatio 17 // * 18 // * This code implementation is the result 19 // * technical work of the GEANT4 collaboratio 20 // * By using, copying, modifying or distri 21 // * any work based on the software) you ag 22 // * use in resulting scientific publicati 23 // * acceptance of all terms of the Geant4 Sof 24 // ******************************************* 25 // 26 // 27 // ------------------------------------------- 28 // 29 // GEANT4 Class header file 30 // 31 // 32 // File name: G4PairProductionRelModel 33 // 34 // Author: Andreas Schaelicke 35 // 36 // Creation date: 02.04.2009 37 // 38 // Modifications: 39 // 28-05-18 New version with improved screenin 40 // LPM function approximation, effici 41 // Corrected call to selecting target 42 // (M. Novak) 43 // 44 // Class Description: 45 // 46 // Implementation of gamma conversion to e+e- 47 // relativistic approximation 48 // 49 50 // ------------------------------------------- 51 // 52 53 #ifndef G4PairProductionRelModel_h 54 #define G4PairProductionRelModel_h 1 55 56 #include <CLHEP/Units/PhysicalConstants.h> 57 58 #include "G4VEmModel.hh" 59 #include "G4Log.hh" 60 #include <vector> 61 62 class G4ParticleChangeForGamma; 63 class G4Pow; 64 65 class G4PairProductionRelModel : public G4VEmM 66 { 67 68 public: 69 70 explicit G4PairProductionRelModel(const G4Pa 71 const G4St 72 73 ~G4PairProductionRelModel() override; 74 75 void Initialise(const G4ParticleDefinition*, 76 77 void InitialiseLocal(const G4ParticleDefinit 78 G4VEmModel* masterModel) override; 79 80 G4double ComputeCrossSectionPerAtom(const G4 81 G4double kinEnergy, 82 G4double Z, 83 G4double A=0., 84 G4double cut=0., 85 G4double emax=DBL_MAX) override; 86 87 void SampleSecondaries(std::vector<G4Dynamic 88 const G4MaterialCutsCouple*, 89 const G4DynamicParticle*, 90 G4double tmin, 91 G4double maxEnergy) override; 92 93 void SetupForMaterial(const G4ParticleDefini 94 const G4Material*,G4double) override; 95 96 inline void SetLPMflag(G4bool val) { fIsUs 97 inline G4bool LPMflag() const { retur 98 99 G4PairProductionRelModel & operator= 100 (const G4PairProductionRelModel &right) = de 101 G4PairProductionRelModel(const G4PairProduc 102 103 protected: 104 105 // for evaluating screening related function 106 inline void ComputePhi12(const G4double delt 107 G4double &phi1, G4double &phi2); 108 inline G4double ScreenFunction1(const G4doub 109 inline G4double ScreenFunction2(const G4doub 110 inline void ScreenFunction12(const G4double 111 G4double &f1, G4double &f2); 112 // helper methods for cross-section computat 113 G4double ComputeParametrizedXSectionPerAtom( 114 G4double ComputeXSectionPerAtom(G4double gam 115 G4double ComputeDXSectionPerAtom(G4double ep 116 G4double Z) 117 G4double ComputeRelDXSectionPerAtom(G4double 118 G4double gammaEnergy, G4double Z 119 120 private: 121 122 // for creating some data structure per Z 123 void InitialiseElementData(); 124 struct ElementData { 125 G4double fLogZ13; 126 G4double fCoulomb; 127 G4double fLradEl; 128 G4double fDeltaFactor; 129 G4double fDeltaMaxLow; 130 G4double fDeltaMaxHigh; 131 G4double fEtaValue; 132 G4double fLPMVarS1Cond; 133 G4double fLPMILVarS1Cond; 134 }; 135 // for precomputing comp. intensive parts of 136 // using them at run-time 137 void InitLPMFunctions(); 138 void ComputeLPMGsPhis(G4double &funcGS, G4do 139 const G4double varShat 140 void GetLPMFunctions(G4double &lpmGs, G4doub 141 void ComputeLPMfunctions(G4double &fXiS, G4d 142 const G4double eps, 143 const G4int izet); 144 struct LPMFuncs { 145 LPMFuncs() : fIsInitialized(false), fISDel 146 G4bool fIsInitialized; 147 G4double fISDelta; 148 G4double fSLimit; 149 std::vector<G4double> fLPMFuncG; 150 std::vector<G4double> fLPMFuncPhi; 151 }; 152 153 protected: 154 static const G4int gMaxZet; 155 // 156 static const G4double gLPMconsta 157 // 158 static const G4double gXGL[8]; 159 static const G4double gWGL[8]; 160 static const G4double gFelLowZet 161 static const G4double gFinelLowZ 162 // 163 static const G4double gXSecFacto 164 static const G4double gEgLPMActi 165 // 166 static std::vector<ElementData*> gElementDa 167 static LPMFuncs gLPMFuncs; 168 // 169 G4bool isFirstInstance{false}; 170 G4bool fIsUseLPMC 171 G4bool fIsUseComp 172 // 173 G4double fLPMEnergy 174 // 175 G4double fParametri 176 G4double fCoulombCo 177 // 178 G4Pow* fG4Calc; 179 G4ParticleDefinition* fTheGamma; 180 G4ParticleDefinition* fTheElectr 181 G4ParticleDefinition* fThePositr 182 G4ParticleChangeForGamma* fParticleC 183 }; 184 // 185 // Bethe screening functions for the elastic ( 186 // Bethe's phi1, phi2 coherent screening funct 187 // by using (the universal) atomic form factor 188 // Fermi model of the atom (using numerical so 189 // screening function instead of Moliere's ana 190 // numerical results can be well approximated 191 // especially near the delta=1 limit) by: 192 // ## if delta <= 1.4 193 // phi1(delta) = 20.806 - delta*(3.190 - 0.57 194 // phi2(delta) = 20.234 - delta*(2.126 - 0.09 195 // ## if delta > 1.4 196 // phi1(delta) = phi2(delta) = 21.0190 - 4.14 197 // with delta = 136mc^2kZ^{-1/3}/[E(Eg-E)] = 1 198 // Eg is the initial photon energy, E is the t 199 // the e-/e+ pair, eps0 = mc^2/Eg and eps = E/ 200 201 inline void G4PairProductionRelModel::ComputeP 202 G4double &phi1, 203 G4double &phi2) 204 { 205 if (delta > 1.4) { 206 phi1 = 21.0190 - 4.145*G4Log(delta + 0.9 207 phi2 = phi1; 208 } else { 209 phi1 = 20.806 - delta*(3.190 - 0.5710*de 210 phi2 = 20.234 - delta*(2.126 - 0.0903*de 211 } 212 } 213 214 // Compute the value of the screening function 215 inline G4double G4PairProductionRelModel::Scre 216 { 217 return (delta > 1.4) ? 42.038 - 8.29*G4Log(d 218 : 42.184 - delta*(7.444 219 } 220 221 // Compute the value of the screening function 222 inline G4double G4PairProductionRelModel::Scre 223 { 224 return (delta > 1.4) ? 42.038 - 8.29*G4Log(d 225 : 41.326 - delta*(5.848 226 } 227 228 // Same as ScreenFunction1 and ScreenFunction2 229 inline void G4PairProductionRelModel::ScreenFu 230 231 { 232 if (delta > 1.4) { 233 f1 = 42.038 - 8.29*G4Log(delta + 0.958); 234 f2 = f1; 235 } else { 236 f1 = 42.184 - delta*(7.444 - 1.623*delta); 237 f2 = 41.326 - delta*(5.848 - 0.902*delta); 238 } 239 } 240 241 #endif 242