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25 // 25 //
>> 26 // $Id: G4hPairProductionModel.cc 66996 2013-01-29 14:50:52Z gcosmo $
26 // 27 //
27 // ------------------------------------------- 28 // -------------------------------------------------------------------
28 // 29 //
29 // GEANT4 Class file 30 // GEANT4 Class file
30 // 31 //
31 // 32 //
32 // File name: G4hPairProductionModel 33 // File name: G4hPairProductionModel
33 // 34 //
34 // Author: Vladimir Ivanchenko on base 35 // Author: Vladimir Ivanchenko on base of G4MuPairProductionModel
35 // 36 //
36 // Creation date: 28.02.2008 37 // Creation date: 28.02.2008
37 // 38 //
38 // Modifications: 39 // Modifications:
39 // 40 //
40 41
41 // 42 //
42 // Class Description: 43 // Class Description:
43 // 44 //
44 // 45 //
45 // ------------------------------------------- 46 // -------------------------------------------------------------------
46 // 47 //
47 //....oooOO0OOooo........oooOO0OOooo........oo 48 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
48 //....oooOO0OOooo........oooOO0OOooo........oo 49 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
49 50
50 #include "G4hPairProductionModel.hh" 51 #include "G4hPairProductionModel.hh"
>> 52 #include "G4PhysicalConstants.hh"
>> 53
>> 54 using namespace std;
51 55
52 G4hPairProductionModel::G4hPairProductionModel 56 G4hPairProductionModel::G4hPairProductionModel(const G4ParticleDefinition* p,
53 const G4String& nam) 57 const G4String& nam)
54 : G4MuPairProductionModel(p, nam) 58 : G4MuPairProductionModel(p, nam)
55 {} 59 {}
>> 60
>> 61 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
>> 62
>> 63 G4hPairProductionModel::~G4hPairProductionModel()
>> 64 {}
>> 65
>> 66 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
>> 67
>> 68 G4double G4hPairProductionModel::ComputeDMicroscopicCrossSection(
>> 69 G4double tkin,
>> 70 G4double Z,
>> 71 G4double pairEnergy)
>> 72 // differential cross section
>> 73 {
>> 74 G4double bbbtf= 183. ;
>> 75 G4double bbbh = 202.4 ;
>> 76 G4double g1tf = 1.95e-5 ;
>> 77 G4double g2tf = 5.3e-5 ;
>> 78 G4double g1h = 4.4e-5 ;
>> 79 G4double g2h = 4.8e-5 ;
>> 80
>> 81 G4double totalEnergy = tkin + particleMass;
>> 82 G4double residEnergy = totalEnergy - pairEnergy;
>> 83 G4double massratio = particleMass/electron_mass_c2 ;
>> 84 G4double massratio2 = massratio*massratio ;
>> 85 G4double cross = 0.;
>> 86
>> 87 SetCurrentElement(Z);
>> 88
>> 89 G4double c3 = 0.75*sqrte*particleMass;
>> 90 if (residEnergy <= c3*z13) return cross;
>> 91
>> 92 G4double c7 = 4.*electron_mass_c2;
>> 93 G4double c8 = 6.*particleMass*particleMass;
>> 94 G4double alf = c7/pairEnergy;
>> 95 G4double a3 = 1. - alf;
>> 96 if (a3 <= 0.) return cross;
>> 97
>> 98 // zeta calculation
>> 99 G4double bbb,g1,g2;
>> 100 if( Z < 1.5 ) { bbb = bbbh ; g1 = g1h ; g2 = g2h ; }
>> 101 else { bbb = bbbtf; g1 = g1tf; g2 = g2tf; }
>> 102
>> 103 G4double zeta = 0;
>> 104 G4double zeta1 = 0.073*log(totalEnergy/(particleMass+g1*z23*totalEnergy))-0.26;
>> 105 if ( zeta1 > 0.)
>> 106 {
>> 107 G4double zeta2 = 0.058*log(totalEnergy/(particleMass+g2*z13*totalEnergy))-0.14;
>> 108 zeta = zeta1/zeta2 ;
>> 109 }
>> 110
>> 111 G4double z2 = Z*(Z+zeta);
>> 112 G4double screen0 = 2.*electron_mass_c2*sqrte*bbb/(z13*pairEnergy);
>> 113 G4double a0 = totalEnergy*residEnergy;
>> 114 G4double a1 = pairEnergy*pairEnergy/a0;
>> 115 G4double bet = 0.5*a1;
>> 116 G4double xi0 = 0.25*massratio2*a1;
>> 117 G4double del = c8/a0;
>> 118
>> 119 G4double rta3 = sqrt(a3);
>> 120 G4double tmnexp = alf/(1. + rta3) + del*rta3;
>> 121 if(tmnexp >= 1.0) return cross;
>> 122
>> 123 G4double tmn = log(tmnexp);
>> 124 G4double sum = 0.;
>> 125
>> 126 // Gaussian integration in ln(1-ro) ( with 8 points)
>> 127 for (G4int i=0; i<8; i++)
>> 128 {
>> 129 G4double a4 = exp(tmn*xgi[i]); // a4 = (1.-asymmetry)
>> 130 G4double a5 = a4*(2.-a4) ;
>> 131 G4double a6 = 1.-a5 ;
>> 132 G4double a7 = 1.+a6 ;
>> 133 G4double a9 = 3.+a6 ;
>> 134 G4double xi = xi0*a5 ;
>> 135 G4double xii = 1./xi ;
>> 136 G4double xi1 = 1.+xi ;
>> 137 G4double screen = screen0*xi1/a5 ;
>> 138 G4double yeu = 5.-a6+4.*bet*a7 ;
>> 139 G4double yed = 2.*(1.+3.*bet)*log(3.+xii)-a6-a1*(2.-a6) ;
>> 140 G4double ye1 = 1.+yeu/yed ;
>> 141 G4double ale=log(bbb/z13*sqrt(xi1*ye1)/(1.+screen*ye1)) ;
>> 142 G4double cre = 0.5*log(1.+2.25*z23*xi1*ye1/massratio2) ;
>> 143 G4double be;
>> 144
>> 145 if (xi <= 1.e3) be = ((2.+a6)*(1.+bet)+xi*a9)*log(1.+xii)+(a5-bet)/xi1-a9;
>> 146 else be = (3.-a6+a1*a7)/(2.*xi);
>> 147
>> 148 G4double fe = (ale-cre)*be;
>> 149 if ( fe < 0.) fe = 0. ;
>> 150
>> 151 G4double ymu = 4.+a6 +3.*bet*a7 ;
>> 152 G4double ymd = a7*(1.5+a1)*log(3.+xi)+1.-1.5*a6 ;
>> 153 G4double ym1 = 1.+ymu/ymd ;
>> 154 G4double alm_crm = log(bbb*massratio/(1.5*z23*(1.+screen*ym1)));
>> 155 G4double a10,bm;
>> 156 if ( xi >= 1.e-3)
>> 157 {
>> 158 a10 = (1.+a1)*a5 ;
>> 159 bm = (a7*(1.+1.5*bet)-a10*xii)*log(xi1)+xi*(a5-bet)/xi1+a10;
>> 160 } else {
>> 161 bm = (5.-a6+bet*a9)*(xi/2.);
>> 162 }
>> 163
>> 164 G4double fm = alm_crm*bm;
>> 165 if ( fm < 0.) fm = 0. ;
>> 166
>> 167 sum += wgi[i]*a4*(fe+fm/massratio2);
>> 168 }
>> 169
>> 170 cross = -tmn*sum*factorForCross*z2*residEnergy/(totalEnergy*pairEnergy);
>> 171
>> 172 return cross;
>> 173 }
56 174
57 //....oooOO0OOooo........oooOO0OOooo........oo 175 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
58 176