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2 | // ******************************************************************** |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: MyMollerBhabhaModel.cc,v 1.1 2007/10/15 16:20:23 maire Exp $ |
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27 | // GEANT4 tag $Name: $ |
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28 | // |
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29 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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30 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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31 | |
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32 | #include "MyMollerBhabhaModel.hh" |
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33 | |
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34 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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35 | |
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36 | using namespace std; |
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37 | |
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38 | MyMollerBhabhaModel::MyMollerBhabhaModel(const G4ParticleDefinition* p, |
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39 | const G4String& nam) |
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40 | : G4MollerBhabhaModel(p,nam) |
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41 | {} |
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42 | |
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43 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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44 | |
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45 | MyMollerBhabhaModel::~MyMollerBhabhaModel() |
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46 | {} |
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47 | |
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48 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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49 | |
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50 | G4double MyMollerBhabhaModel::ComputeDEDXPerVolume( |
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51 | const G4Material* material, |
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52 | const G4ParticleDefinition* p, |
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53 | G4double kineticEnergy, |
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54 | G4double cutEnergy) |
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55 | { |
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56 | if(!particle) SetParticle(p); |
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57 | // calculate the dE/dx due to the ionization by Seltzer-Berger formula |
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58 | |
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59 | G4double electronDensity = material->GetElectronDensity(); |
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60 | G4double Zeff = electronDensity/material->GetTotNbOfAtomsPerVolume(); |
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61 | G4double th = 0.25*sqrt(Zeff)*keV; |
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62 | G4double tkin = kineticEnergy; |
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63 | G4bool lowEnergy = false; |
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64 | if (kineticEnergy < th) { |
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65 | tkin = th; |
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66 | lowEnergy = true; |
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67 | } |
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68 | G4double tau = tkin/electron_mass_c2; |
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69 | G4double gam = tau + 1.0; |
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70 | G4double gamma2= gam*gam; |
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71 | G4double beta2 = 1. - 1./gamma2; |
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72 | //G4double bg2 = beta2*gamma2; |
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73 | |
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74 | G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy(); |
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75 | eexc /= electron_mass_c2; |
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76 | G4double eexc2 = eexc*eexc; |
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77 | |
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78 | G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2; |
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79 | G4double dedx; |
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80 | |
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81 | // electron |
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82 | if (isElectron) { |
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83 | |
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84 | dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2 |
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85 | + log((tau-d)*d) + tau/(tau-d) |
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86 | + (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2; |
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87 | |
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88 | //positron |
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89 | } else { |
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90 | |
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91 | G4double d2 = d*d*0.5; |
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92 | G4double d3 = d2*d/1.5; |
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93 | G4double d4 = d3*d*3.75; |
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94 | G4double y = 1.0/(1.0 + gam); |
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95 | dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d) |
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96 | - beta2*(tau + 2.0*d - y*(3.0*d2 |
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97 | + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau; |
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98 | } |
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99 | |
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100 | //do not apply density correction |
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101 | //G4double cden = material->GetIonisation()->GetCdensity(); |
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102 | //G4double mden = material->GetIonisation()->GetMdensity(); |
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103 | //G4double aden = material->GetIonisation()->GetAdensity(); |
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104 | //G4double x0den = material->GetIonisation()->GetX0density(); |
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105 | //G4double x1den = material->GetIonisation()->GetX1density(); |
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106 | //G4double x = log(bg2)/twoln10; |
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107 | |
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108 | //if (x >= x0den) { |
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109 | // dedx -= twoln10*x - cden; |
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110 | // if (x < x1den) dedx -= aden*pow(x1den-x, mden); |
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111 | //} |
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112 | |
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113 | // now you can compute the total ionization loss |
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114 | dedx *= twopi_mc2_rcl2*electronDensity/beta2; |
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115 | if (dedx < 0.0) dedx = 0.0; |
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116 | |
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117 | // lowenergy extrapolation |
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118 | |
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119 | if (lowEnergy) { |
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120 | |
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121 | if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy); |
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122 | else dedx *= sqrt(tkin*kineticEnergy)/lowLimit; |
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123 | |
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124 | } |
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125 | return dedx; |
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126 | } |
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127 | |
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128 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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