[819] | 1 | // |
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| 2 | // ******************************************************************** |
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| 3 | // * License and Disclaimer * |
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| 4 | // * * |
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| 5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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| 7 | // * conditions of the Geant4 Software License, included in the file * |
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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| 9 | // * include a list of copyright holders. * |
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| 10 | // * * |
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| 11 | // * Neither the authors of this software system, nor their employing * |
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| 12 | // * institutes,nor the agencies providing financial support for this * |
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| 13 | // * work make any representation or warranty, express or implied, * |
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| 14 | // * regarding this software system or assume any liability for its * |
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| 15 | // * use. Please see the license in the file LICENSE and URL above * |
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| 16 | // * for the full disclaimer and the limitation of liability. * |
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| 17 | // * * |
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| 18 | // * This code implementation is the result of the scientific and * |
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| 19 | // * technical work of the GEANT4 collaboration. * |
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| 20 | // * By using, copying, modifying or distributing the software (or * |
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| 21 | // * any work based on the software) you agree to acknowledge its * |
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| 22 | // * use in resulting scientific publications, and indicate your * |
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| 23 | // * acceptance of all terms of the Geant4 Software license. * |
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| 24 | // ******************************************************************** |
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| 25 | // |
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[1315] | 26 | // $Id: G4MollerBhabhaModel.cc,v 1.38 2010/04/06 17:10:16 vnivanch Exp $ |
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[1337] | 27 | // GEANT4 tag $Name: geant4-09-04-beta-01 $ |
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[819] | 28 | // |
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| 29 | // ------------------------------------------------------------------- |
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| 30 | // |
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| 31 | // GEANT4 Class file |
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| 32 | // |
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| 33 | // |
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| 34 | // File name: G4MollerBhabhaModel |
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| 35 | // |
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| 36 | // Author: Vladimir Ivanchenko on base of Laszlo Urban code |
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| 37 | // |
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| 38 | // Creation date: 03.01.2002 |
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| 39 | // |
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| 40 | // Modifications: |
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| 41 | // |
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| 42 | // 13-11-02 Minor fix - use normalised direction (V.Ivanchenko) |
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| 43 | // 04-12-02 Change G4DynamicParticle constructor in PostStepDoIt (V.Ivanchenko) |
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| 44 | // 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko) |
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| 45 | // 27-01-03 Make models region aware (V.Ivanchenko) |
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| 46 | // 13-02-03 Add name (V.Ivanchenko) |
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| 47 | // 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko) |
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| 48 | // 25-07-05 Add protection in calculation of recoil direction for the case |
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| 49 | // of complete energy transfer from e+ to e- (V.Ivanchenko) |
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| 50 | // 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma) |
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| 51 | // 15-05-06 Fix MinEnergyCut (V.Ivanchenko) |
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| 52 | // |
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| 53 | // |
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| 54 | // Class Description: |
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| 55 | // |
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| 56 | // Implementation of energy loss and delta-electron production by e+/e- |
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| 57 | // |
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| 58 | // ------------------------------------------------------------------- |
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| 59 | // |
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| 60 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 61 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 62 | |
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| 63 | #include "G4MollerBhabhaModel.hh" |
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| 64 | #include "G4Electron.hh" |
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| 65 | #include "G4Positron.hh" |
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| 66 | #include "Randomize.hh" |
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| 67 | #include "G4ParticleChangeForLoss.hh" |
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| 68 | |
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| 69 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 70 | |
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| 71 | using namespace std; |
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| 72 | |
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| 73 | G4MollerBhabhaModel::G4MollerBhabhaModel(const G4ParticleDefinition* p, |
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| 74 | const G4String& nam) |
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| 75 | : G4VEmModel(nam), |
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[1055] | 76 | particle(0), |
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| 77 | isElectron(true), |
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| 78 | twoln10(2.0*log(10.0)), |
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| 79 | lowLimit(0.2*keV), |
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| 80 | isInitialised(false) |
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[819] | 81 | { |
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| 82 | theElectron = G4Electron::Electron(); |
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| 83 | if(p) SetParticle(p); |
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| 84 | } |
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| 85 | |
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| 86 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 87 | |
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| 88 | G4MollerBhabhaModel::~G4MollerBhabhaModel() |
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| 89 | {} |
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| 90 | |
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| 91 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 92 | |
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| 93 | G4double G4MollerBhabhaModel::MinEnergyCut(const G4ParticleDefinition*, |
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[1315] | 94 | const G4MaterialCutsCouple* /*couple*/) |
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[819] | 95 | { |
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[1315] | 96 | // G4double electronDensity = couple->GetMaterial()->GetElectronDensity(); |
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| 97 | //G4double Zeff = electronDensity/couple->GetMaterial()->GetTotNbOfAtomsPerVolume(); |
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| 98 | //return 0.25*sqrt(Zeff)*keV; |
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| 99 | //return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy(); |
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| 100 | return 0.1*keV; |
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[819] | 101 | } |
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| 102 | |
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| 103 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 104 | |
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[1055] | 105 | G4double G4MollerBhabhaModel::MaxSecondaryEnergy(const G4ParticleDefinition*, |
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| 106 | G4double kinEnergy) |
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| 107 | { |
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| 108 | G4double tmax = kinEnergy; |
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| 109 | if(isElectron) tmax *= 0.5; |
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| 110 | return tmax; |
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| 111 | } |
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| 112 | |
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| 113 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 114 | |
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[819] | 115 | void G4MollerBhabhaModel::Initialise(const G4ParticleDefinition* p, |
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| 116 | const G4DataVector&) |
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| 117 | { |
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| 118 | if(!particle) SetParticle(p); |
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[1055] | 119 | SetDeexcitationFlag(false); |
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| 120 | |
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| 121 | if(isInitialised) return; |
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| 122 | |
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| 123 | isInitialised = true; |
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| 124 | fParticleChange = GetParticleChangeForLoss(); |
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[819] | 125 | } |
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| 126 | |
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| 127 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 128 | |
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| 129 | G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron( |
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| 130 | const G4ParticleDefinition* p, |
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| 131 | G4double kineticEnergy, |
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| 132 | G4double cutEnergy, |
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| 133 | G4double maxEnergy) |
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| 134 | { |
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| 135 | if(!particle) SetParticle(p); |
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| 136 | |
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| 137 | G4double cross = 0.0; |
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| 138 | G4double tmax = MaxSecondaryEnergy(p, kineticEnergy); |
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| 139 | tmax = min(maxEnergy, tmax); |
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| 140 | |
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| 141 | if(cutEnergy < tmax) { |
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| 142 | |
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| 143 | G4double xmin = cutEnergy/kineticEnergy; |
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| 144 | G4double xmax = tmax/kineticEnergy; |
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| 145 | G4double gam = kineticEnergy/electron_mass_c2 + 1.0; |
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| 146 | G4double gamma2= gam*gam; |
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| 147 | G4double beta2 = 1.0 - 1.0/gamma2; |
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| 148 | |
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| 149 | //Moller (e-e-) scattering |
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| 150 | if (isElectron) { |
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| 151 | |
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| 152 | G4double g = (2.0*gam - 1.0)/gamma2; |
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| 153 | cross = ((xmax - xmin)*(1.0 - g + 1.0/(xmin*xmax) |
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| 154 | + 1.0/((1.0-xmin)*(1.0 - xmax))) |
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| 155 | - g*log( xmax*(1.0 - xmin)/(xmin*(1.0 - xmax)) ) ) / beta2; |
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| 156 | |
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| 157 | //Bhabha (e+e-) scattering |
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| 158 | } else { |
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| 159 | |
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| 160 | G4double y = 1.0/(1.0 + gam); |
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| 161 | G4double y2 = y*y; |
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| 162 | G4double y12 = 1.0 - 2.0*y; |
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| 163 | G4double b1 = 2.0 - y2; |
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| 164 | G4double b2 = y12*(3.0 + y2); |
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| 165 | G4double y122= y12*y12; |
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| 166 | G4double b4 = y122*y12; |
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| 167 | G4double b3 = b4 + y122; |
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| 168 | |
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| 169 | cross = (xmax - xmin)*(1.0/(beta2*xmin*xmax) + b2 |
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| 170 | - 0.5*b3*(xmin + xmax) |
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| 171 | + b4*(xmin*xmin + xmin*xmax + xmax*xmax)/3.0) |
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| 172 | - b1*log(xmax/xmin); |
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| 173 | } |
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| 174 | |
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| 175 | cross *= twopi_mc2_rcl2/kineticEnergy; |
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| 176 | } |
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| 177 | return cross; |
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| 178 | } |
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| 179 | |
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| 180 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 181 | |
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| 182 | G4double G4MollerBhabhaModel::ComputeCrossSectionPerAtom( |
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| 183 | const G4ParticleDefinition* p, |
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| 184 | G4double kineticEnergy, |
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| 185 | G4double Z, G4double, |
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| 186 | G4double cutEnergy, |
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| 187 | G4double maxEnergy) |
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| 188 | { |
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| 189 | G4double cross = Z*ComputeCrossSectionPerElectron |
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| 190 | (p,kineticEnergy,cutEnergy,maxEnergy); |
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| 191 | return cross; |
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| 192 | } |
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| 193 | |
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| 194 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 195 | |
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| 196 | G4double G4MollerBhabhaModel::CrossSectionPerVolume( |
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| 197 | const G4Material* material, |
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| 198 | const G4ParticleDefinition* p, |
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| 199 | G4double kineticEnergy, |
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| 200 | G4double cutEnergy, |
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| 201 | G4double maxEnergy) |
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| 202 | { |
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| 203 | G4double eDensity = material->GetElectronDensity(); |
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| 204 | G4double cross = eDensity*ComputeCrossSectionPerElectron |
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| 205 | (p,kineticEnergy,cutEnergy,maxEnergy); |
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| 206 | return cross; |
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| 207 | } |
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| 208 | |
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| 209 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 210 | |
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| 211 | G4double G4MollerBhabhaModel::ComputeDEDXPerVolume( |
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| 212 | const G4Material* material, |
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| 213 | const G4ParticleDefinition* p, |
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| 214 | G4double kineticEnergy, |
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| 215 | G4double cutEnergy) |
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| 216 | { |
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| 217 | if(!particle) SetParticle(p); |
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| 218 | // calculate the dE/dx due to the ionization by Seltzer-Berger formula |
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| 219 | |
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| 220 | G4double electronDensity = material->GetElectronDensity(); |
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| 221 | G4double Zeff = electronDensity/material->GetTotNbOfAtomsPerVolume(); |
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| 222 | G4double th = 0.25*sqrt(Zeff)*keV; |
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| 223 | G4double tkin = kineticEnergy; |
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| 224 | G4bool lowEnergy = false; |
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| 225 | if (kineticEnergy < th) { |
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| 226 | tkin = th; |
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| 227 | lowEnergy = true; |
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| 228 | } |
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| 229 | G4double tau = tkin/electron_mass_c2; |
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| 230 | G4double gam = tau + 1.0; |
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| 231 | G4double gamma2= gam*gam; |
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| 232 | G4double beta2 = 1. - 1./gamma2; |
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| 233 | G4double bg2 = beta2*gamma2; |
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| 234 | |
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| 235 | G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy(); |
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| 236 | eexc /= electron_mass_c2; |
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| 237 | G4double eexc2 = eexc*eexc; |
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| 238 | |
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| 239 | G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2; |
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| 240 | G4double dedx; |
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| 241 | |
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| 242 | // electron |
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| 243 | if (isElectron) { |
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| 244 | |
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| 245 | dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2 |
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| 246 | + log((tau-d)*d) + tau/(tau-d) |
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| 247 | + (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2; |
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| 248 | |
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| 249 | //positron |
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| 250 | } else { |
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| 251 | |
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| 252 | G4double d2 = d*d*0.5; |
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| 253 | G4double d3 = d2*d/1.5; |
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| 254 | G4double d4 = d3*d*3.75; |
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| 255 | G4double y = 1.0/(1.0 + gam); |
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| 256 | dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d) |
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| 257 | - beta2*(tau + 2.0*d - y*(3.0*d2 |
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| 258 | + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau; |
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| 259 | } |
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| 260 | |
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| 261 | //density correction |
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[1196] | 262 | //G4double cden = material->GetIonisation()->GetCdensity(); |
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| 263 | //G4double mden = material->GetIonisation()->GetMdensity(); |
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| 264 | //G4double aden = material->GetIonisation()->GetAdensity(); |
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| 265 | //G4double x0den = material->GetIonisation()->GetX0density(); |
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| 266 | //G4double x1den = material->GetIonisation()->GetX1density(); |
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[819] | 267 | G4double x = log(bg2)/twoln10; |
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| 268 | |
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[1196] | 269 | //if (x >= x0den) { |
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| 270 | // dedx -= twoln10*x - cden; |
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| 271 | // if (x < x1den) dedx -= aden*pow(x1den-x, mden); |
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| 272 | //} |
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| 273 | dedx -= material->GetIonisation()->DensityCorrection(x); |
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[819] | 274 | |
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| 275 | // now you can compute the total ionization loss |
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| 276 | dedx *= twopi_mc2_rcl2*electronDensity/beta2; |
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| 277 | if (dedx < 0.0) dedx = 0.0; |
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| 278 | |
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| 279 | // lowenergy extrapolation |
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| 280 | |
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| 281 | if (lowEnergy) { |
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| 282 | |
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| 283 | if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy); |
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| 284 | else dedx *= sqrt(tkin*kineticEnergy)/lowLimit; |
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| 285 | |
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| 286 | } |
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| 287 | return dedx; |
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| 288 | } |
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| 289 | |
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| 290 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 291 | |
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| 292 | void G4MollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp, |
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| 293 | const G4MaterialCutsCouple*, |
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| 294 | const G4DynamicParticle* dp, |
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| 295 | G4double tmin, |
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| 296 | G4double maxEnergy) |
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| 297 | { |
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[1055] | 298 | G4double kineticEnergy = dp->GetKineticEnergy(); |
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| 299 | G4double tmax = kineticEnergy; |
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| 300 | if(isElectron) tmax *= 0.5; |
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| 301 | if(maxEnergy < tmax) tmax = maxEnergy; |
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[819] | 302 | if(tmin >= tmax) return; |
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| 303 | |
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| 304 | G4double energy = kineticEnergy + electron_mass_c2; |
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| 305 | G4double totalMomentum = sqrt(kineticEnergy*(energy + electron_mass_c2)); |
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| 306 | G4double xmin = tmin/kineticEnergy; |
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| 307 | G4double xmax = tmax/kineticEnergy; |
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| 308 | G4double gam = energy/electron_mass_c2; |
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| 309 | G4double gamma2 = gam*gam; |
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| 310 | G4double beta2 = 1.0 - 1.0/gamma2; |
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| 311 | G4double x, z, q, grej; |
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| 312 | |
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| 313 | G4ThreeVector direction = dp->GetMomentumDirection(); |
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| 314 | |
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| 315 | //Moller (e-e-) scattering |
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| 316 | if (isElectron) { |
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| 317 | |
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| 318 | G4double g = (2.0*gam - 1.0)/gamma2; |
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| 319 | G4double y = 1.0 - xmax; |
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| 320 | grej = 1.0 - g*xmax + xmax*xmax*(1.0 - g + (1.0 - g*y)/(y*y)); |
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| 321 | |
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| 322 | do { |
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| 323 | q = G4UniformRand(); |
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| 324 | x = xmin*xmax/(xmin*(1.0 - q) + xmax*q); |
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| 325 | y = 1.0 - x; |
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| 326 | z = 1.0 - g*x + x*x*(1.0 - g + (1.0 - g*y)/(y*y)); |
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| 327 | /* |
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| 328 | if(z > grej) { |
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| 329 | G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! " |
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| 330 | << "Majorant " << grej << " < " |
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| 331 | << z << " for x= " << x |
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| 332 | << " e-e- scattering" |
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| 333 | << G4endl; |
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| 334 | } |
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| 335 | */ |
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| 336 | } while(grej * G4UniformRand() > z); |
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| 337 | |
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| 338 | //Bhabha (e+e-) scattering |
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| 339 | } else { |
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| 340 | |
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| 341 | G4double y = 1.0/(1.0 + gam); |
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| 342 | G4double y2 = y*y; |
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| 343 | G4double y12 = 1.0 - 2.0*y; |
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| 344 | G4double b1 = 2.0 - y2; |
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| 345 | G4double b2 = y12*(3.0 + y2); |
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| 346 | G4double y122= y12*y12; |
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| 347 | G4double b4 = y122*y12; |
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| 348 | G4double b3 = b4 + y122; |
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| 349 | |
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[1055] | 350 | y = xmax*xmax; |
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| 351 | grej = 1.0 + (y*y*b4 - xmin*xmin*xmin*b3 + y*b2 - xmin*b1)*beta2; |
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[819] | 352 | do { |
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[1055] | 353 | q = G4UniformRand(); |
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| 354 | x = xmin*xmax/(xmin*(1.0 - q) + xmax*q); |
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| 355 | y = x*x; |
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| 356 | z = 1.0 + (y*y*b4 - x*y*b3 + y*b2 - x*b1)*beta2; |
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[819] | 357 | /* |
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| 358 | if(z > grej) { |
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| 359 | G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! " |
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| 360 | << "Majorant " << grej << " < " |
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| 361 | << z << " for x= " << x |
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| 362 | << " e+e- scattering" |
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| 363 | << G4endl; |
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| 364 | } |
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| 365 | */ |
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| 366 | } while(grej * G4UniformRand() > z); |
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| 367 | } |
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| 368 | |
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| 369 | G4double deltaKinEnergy = x * kineticEnergy; |
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| 370 | |
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| 371 | G4double deltaMomentum = |
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| 372 | sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2)); |
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| 373 | G4double cost = deltaKinEnergy * (energy + electron_mass_c2) / |
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| 374 | (deltaMomentum * totalMomentum); |
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| 375 | G4double sint = 1.0 - cost*cost; |
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| 376 | if(sint > 0.0) sint = sqrt(sint); |
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| 377 | |
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| 378 | G4double phi = twopi * G4UniformRand() ; |
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| 379 | |
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| 380 | G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ; |
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| 381 | deltaDirection.rotateUz(direction); |
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| 382 | |
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| 383 | // primary change |
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| 384 | kineticEnergy -= deltaKinEnergy; |
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| 385 | fParticleChange->SetProposedKineticEnergy(kineticEnergy); |
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| 386 | |
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| 387 | if(kineticEnergy > DBL_MIN) { |
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| 388 | G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection; |
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| 389 | direction = dir.unit(); |
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| 390 | fParticleChange->SetProposedMomentumDirection(direction); |
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| 391 | } |
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| 392 | |
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| 393 | // create G4DynamicParticle object for delta ray |
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| 394 | G4DynamicParticle* delta = new G4DynamicParticle(theElectron, |
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[1055] | 395 | deltaDirection,deltaKinEnergy); |
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[819] | 396 | vdp->push_back(delta); |
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| 397 | } |
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| 398 | |
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| 399 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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