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G4QElectronNuclearCrossSection.hh
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27 // GEANT4 tag $Name: not supported by cvs2svn $
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29 //
30 // GEANT4 physics class: G4QElectronNuclearCrossSection -- header file
31 // M.V. Kossov, ITEP(Moscow), 24-OCT-01
32 // The last update: M.V. Kossov, CERN/ITEP (Moscow) 25-Sept-03
33 //
34 // --------------------------------------------------------------------------------
35 // Short description: reaction cross-sections for electron-nuclear reactions, which
36 // are integrals over virtual equivalent photons photons.
37 // --------------------------------------------------------------------------------
38 
39 #ifndef G4QElectronNuclearCrossSection_h
40 #define G4QElectronNuclearCrossSection_h 1
41 
42 #include <vector>
43 #include "Randomize.hh"
44 #include "G4VQCrossSection.hh"
45 
46 class G4QElectronNuclearCrossSection : public G4VQCrossSection
47 {
48 protected:
49 
50  G4QElectronNuclearCrossSection() {} // Constructor
51 
52 public:
53 
54  ~G4QElectronNuclearCrossSection();
55 
56  static G4VQCrossSection* GetPointer(); // Gives a pointer to this singletone
57 
58  G4double ThresholdEnergy(G4int Z, G4int N, G4int PDG=11);
59 
60  // At present momentum (pMom) must be in GeV (@@ Units)
61  virtual G4double GetCrossSection(G4bool fCS, G4double pMom, G4int tgZ, G4int tgN,
62  G4int pPDG=0);
63 
64  G4double CalculateCrossSection(G4bool CS, G4int F, G4int I, G4int PDG, G4int Z, G4int N,
65  G4double Momentum);
66 
67  G4int GetExchangePDGCode();
68 
69  G4double GetExchangeEnergy();
70 
71  G4double GetVirtualFactor(G4double nu, G4double Q2);
72 
73  G4double GetExchangeQ2(G4double nu);
74 
75 private:
76  G4int GetFunctions(G4double a, G4double* x, G4double* y, G4double* z);
77  G4double HighEnergyJ1(G4double lE);
78  G4double HighEnergyJ2(G4double lE);
79  G4double HighEnergyJ3(G4double lE);
80  G4double SolveTheEquation(G4double f);
81  G4double Fun(G4double x);
82  G4double DFun(G4double x);
83 
84 // Body
85 private:
86  static G4bool onlyCS; // flag to calculate only CrossSection
87  static G4double lastSig; // Last calculated cross section
88  static G4int lastL; // Last used in the cross section TheLastBin
89  static G4double lastE; // Last used in the cross section Energy
90  static G4int lastF; // Last used in the cross section TheFirstBin
91  static G4double lastG; // Last value of gamma=lnE-ln(m)
92  static G4double lastH; // Last value of the High energy A-dependence
93  static G4double* lastJ1; // Pointer to the last array of the J1 function
94  static G4double* lastJ2; // Pointer to the last array of the J2 function
95  static G4double* lastJ3; // Pointer to the last array of the J3 function
96  static G4int lastPDG; // The last projectile PDG
97  static G4int lastN; // The last N of calculated nucleus
98  static G4int lastZ; // The last Z of calculated nucleus
99  static G4double lastP; // Last used in the cross section Momentum
100  static G4double lastTH; // Last value of the Momentum Threshold
101  static G4double lastCS; // Last value of the Cross Section
102  static G4int lastI; // The last position in the DAMDB
103  static std::vector <G4double*>* J1; // Vector of pointers to the J1 tabulated functions
104  static std::vector <G4double*>* J2; // Vector of pointers to the J2 tabulated functions
105  static std::vector <G4double*>* J3; // Vector of pointers to the J3 tabulated functions
106 };
107 
108 inline G4double G4QElectronNuclearCrossSection::DFun(G4double x)//PhotoNucCSParametrization
109 {
110  static const G4double shd=1.0734; // HE PomShadowing(D)
111  static const G4double poc=0.0375; // HE Pomeron coefficient
112  static const G4double pos=16.5; // HE Pomeron shift
113  static const G4double reg=.11; // HE Reggeon slope
114  static const G4double mel=0.5109989; // Mass of an electron in MeV
115  static const G4double lmel=std::log(mel); // Log of an electron mass
116  G4double y=std::exp(x-lastG-lmel); // y for the x
117  G4double flux=lastG*(2.-y*(2.-y))-1.; // flux factor
118  return (poc*(x-pos)+shd*std::exp(-reg*x))*flux;
119 }
120 
121 inline G4double G4QElectronNuclearCrossSection::Fun(G4double x) // Integrated PhoNucCS
122 {
123  G4double dlg1=lastG+lastG-1.;
124  G4double lgoe=lastG/lastE;
125  G4double HE2=HighEnergyJ2(x);
126  return dlg1*HighEnergyJ1(x)-lgoe*(HE2+HE2-HighEnergyJ3(x)/lastE);
127 }
128 
129 inline G4double G4QElectronNuclearCrossSection::HighEnergyJ1(G4double lEn)
130 {
131  static const G4double le=std::log(50000.); // log(E0)
132  static const G4double le2=le*le; // log(E0)^2
133  static const G4double a=.0375; // a
134  static const G4double ha=a*.5; // a/2
135  static const G4double ab=a*16.5; // a*b
136  static const G4double d=0.11; // d
137  static const G4double cd=1.0734/d; // c/d
138  static const G4double ele=std::exp(-d*le); // E0^(-d)
139  return ha*(lEn*lEn-le2)-ab*(lEn-le)-cd*(std::exp(-d*lEn)-ele);
140 }
141 
142 inline G4double G4QElectronNuclearCrossSection::HighEnergyJ2(G4double lEn)
143 {
144  static const G4double e=50000.; // E0
145  static const G4double le=std::log(e); // log(E0)
146  static const G4double le1=(le-1.)*e; // (log(E0)-1)*E0
147  static const G4double a=.0375; // a
148  static const G4double ab=a*16.5; // a*b
149  static const G4double d=1.-0.11; // 1-d
150  static const G4double cd=1.0734/d; // c/(1-d)
151  static const G4double ele=std::exp(d*le); // E0^(1-d)
152  G4double En=std::exp(lEn);
153  return a*((lEn-1.)*En-le1)-ab*(En-e)+cd*(std::exp(d*lEn)-ele);
154 }
155 
156 inline G4double G4QElectronNuclearCrossSection::HighEnergyJ3(G4double lEn)
157 {
158  static const G4double e=50000.; // E0
159  static const G4double le=std::log(e); // log(E0)
160  static const G4double e2=e*e; // E0^2
161  static const G4double leh=(le-.5)*e2; // (log(E0)-.5)*E0^2
162  static const G4double ha=.0375*.5; // a/2
163  static const G4double hab=ha*16.5; // a*b/2
164  static const G4double d=2.-.11; // 2-d
165  static const G4double cd=1.0734/d; // c/(2-d)
166  static const G4double ele=std::exp(d*le); // E0^(2-d)
167  G4double lastE2=std::exp(lEn+lEn);
168  return ha*((lEn-.5)*lastE2-leh)-hab*(lastE2-e2)+cd*(std::exp(d*lEn)-ele);
169 }
170 
171 #endif
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