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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: G4BetheHeitlerModel 33 // 34 // Author: Vladimir Ivanchenko on base 35 // 36 // Creation date: 19.04.2005 37 // 38 // Modifications by Vladimir Ivanchenko, Miche 39 // 40 // Class Description: 41 // 42 // Implementation of gamma conversion to e+e- 43 // For details see Physics Reference Manual 44 45 // ------------------------------------------- 46 // 47 48 #ifndef G4BetheHeitlerModel_h 49 #define G4BetheHeitlerModel_h 1 50 51 #include "G4VEmModel.hh" 52 #include "G4PhysicsTable.hh" 53 #include "G4Log.hh" 54 55 #include <vector> 56 57 class G4ParticleChangeForGamma; 58 class G4Pow; 59 class G4EmElementXS; 60 61 class G4BetheHeitlerModel : public G4VEmModel 62 { 63 64 public: 65 66 explicit G4BetheHeitlerModel(const G4Particl 67 const G4String& 68 69 ~G4BetheHeitlerModel() override; 70 71 void Initialise(const G4ParticleDefinition*, 72 73 void InitialiseLocal(const G4ParticleDefinit 74 G4VEmModel* masterModel) override; 75 76 G4double ComputeCrossSectionPerAtom(const G4 77 G4double kinEnergy, 78 G4double Z, 79 G4double A=0., 80 G4double cut=0., 81 G4double emax=DBL_MAX) override; 82 83 void SampleSecondaries(std::vector<G4Dynamic 84 const G4MaterialCutsCouple*, 85 const G4DynamicParticle*, 86 G4double tmin, 87 G4double maxEnergy) override; 88 89 // hide assignment operator 90 G4BetheHeitlerModel & operator=(const G4Beth 91 G4BetheHeitlerModel(const G4BetheHeitlerMod 92 93 protected: 94 95 inline G4double ScreenFunction1(const G4doub 96 97 inline G4double ScreenFunction2(const G4doub 98 99 inline void ScreenFunction12(const G4double 100 101 void InitialiseElementData(); 102 103 struct ElementData { 104 G4double fDeltaMaxLow; 105 G4double fDeltaMaxHigh; 106 }; 107 108 static const G4int gMaxZet; 109 110 G4Pow* fG4Calc; 111 const G4ParticleDefinition* fTheGamma; 112 const G4ParticleDefinition* fTheElectr 113 const G4ParticleDefinition* fThePositr 114 G4ParticleChangeForGamma* fParticleC 115 G4EmElementXS* fXSection{ 116 117 G4bool isFirstInstance{false}; 118 G4bool useEPICS2017{false}; 119 120 static std::vector<ElementData*> gElementDa 121 }; 122 123 // 124 // Bethe screening functions for the elastic ( 125 // Bethe's phi1, phi2 coherent screening funct 126 // by using (the universal) atomic form factor 127 // Fermi model of the atom (using numerical so 128 // screening function instead of Moliere's ana 129 // numerical results can be well approximated 130 // especially near the delta=1 limit) by: 131 // ## if delta <= 1.4 132 // phi1(delta) = 20.806 - delta*(3.190 - 0.57 133 // phi2(delta) = 20.234 - delta*(2.126 - 0.09 134 // ## if delta > 1.4 135 // phi1(delta) = phi2(delta) = 21.0190 - 4.14 136 // with delta = 136mc^2kZ^{-1/3}/[E(Eg-E)] = 1 137 // Eg is the initial photon energy, E is the t 138 // the e-/e+ pair, eps0 = mc^2/Eg and eps = E/ 139 140 // Compute the value of the screening function 141 inline G4double G4BetheHeitlerModel::ScreenFun 142 { 143 return (delta > 1.4) ? 42.038 - 8.29*G4Log(d 144 : 42.184 - delta*(7.444 145 } 146 147 // Compute the value of the screening function 148 inline G4double G4BetheHeitlerModel::ScreenFun 149 { 150 return (delta > 1.4) ? 42.038 - 8.29*G4Log(d 151 : 41.326 - delta*(5.848 152 } 153 154 // Same as ScreenFunction1 and ScreenFunction2 155 inline void G4BetheHeitlerModel::ScreenFunctio 156 157 { 158 if (delta > 1.4) { 159 f1 = 42.038 - 8.29*G4Log(delta + 0.958); 160 f2 = f1; 161 } else { 162 f1 = 42.184 - delta*(7.444 - 1.623*delta); 163 f2 = 41.326 - delta*(5.848 - 0.902*delta); 164 } 165 } 166 167 #endif 168