[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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| 26 | // |
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| 27 | // $Id: G4MuonNucleusInteractionModel.cc,v 1.6 2006/06/29 20:57:36 gunter Exp $ |
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[1228] | 28 | // GEANT4 tag $Name: geant4-09-03 $ |
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[819] | 29 | // |
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| 30 | // -------------------------------------------------------------- |
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| 31 | // G4MuonNucleusInteractionModel.cc |
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| 32 | // |
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| 33 | // M.Takahata (Makoto.Takahata@cern.ch) |
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| 34 | |
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| 35 | #include "G4MuonNucleusInteractionModel.hh" |
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| 36 | |
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| 37 | |
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| 38 | //----------------------------------------------------------------------------- |
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| 39 | G4MuonNucleusInteractionModel::G4MuonNucleusInteractionModel() |
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| 40 | : G4LeptonHadronInteractionModel() |
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| 41 | //----------------------------------------------------------------------------- |
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| 42 | { |
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| 43 | // build the physics vector |
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| 44 | Nbin = 90; |
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| 45 | kEmin = 1.0e-5*GeV; |
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| 46 | kEmax = 1.0e+4*GeV; |
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| 47 | cascadeModelMarginalEnergy = 25.0*GeV; |
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| 48 | theCoefficientVector = new G4PhysicsLogVector(kEmin, kEmax, Nbin); |
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| 49 | makePhysicsVector(); |
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| 50 | |
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| 51 | // construct variables |
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| 52 | LEPionMinusInelastic = new G4LEPionMinusInelastic; |
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| 53 | LEPionPlusInelastic = new G4LEPionPlusInelastic; |
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| 54 | HEPionMinusInelastic = new G4HEPionMinusInelastic; |
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| 55 | HEPionPlusInelastic = new G4HEPionPlusInelastic; |
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| 56 | } |
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| 57 | |
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| 58 | |
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| 59 | //----------------------------------------------------------------------------- |
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| 60 | G4MuonNucleusInteractionModel::~G4MuonNucleusInteractionModel() |
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| 61 | //----------------------------------------------------------------------------- |
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| 62 | { |
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| 63 | delete LEPionMinusInelastic; |
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| 64 | delete LEPionPlusInelastic; |
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| 65 | delete HEPionMinusInelastic; |
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| 66 | delete HEPionPlusInelastic; |
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| 67 | |
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| 68 | delete theCoefficientVector; |
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| 69 | } |
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| 70 | |
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| 71 | |
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| 72 | //----------------------------------------------------------------------------- |
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| 73 | G4double G4MuonNucleusInteractionModel::tetal[35] = { |
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| 74 | //----------------------------------------------------------------------------- |
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| 75 | 1.0000000, 0.9999995, 0.9999990, 0.9999981, 0.9999962, |
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| 76 | 0.9999943, 0.9999905, 0.9999847, 0.9999752, 0.9999599, |
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| 77 | 0.9999352, 0.9998951, 0.9998302, 0.9997253, 0.9995556, |
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| 78 | 0.9992810, 0.9988368, 0.9981183, 0.9969561, 0.9950773, |
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| 79 | 0.9920409, 0.9871377, 0.9792297, 0.9665010, 0.9460785, |
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| 80 | 0.9134827, 0.8618938, 0.7813507, 0.6583430, 0.4770452, |
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| 81 | 0.2247237, -0.0955139, -0.4461272, -0.7495149, -0.9900000 |
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| 82 | }; |
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| 83 | |
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| 84 | |
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| 85 | //----------------------------------------------------------------------------- |
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| 86 | G4double G4MuonNucleusInteractionModel::xeml[23] = { |
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| 87 | //----------------------------------------------------------------------------- |
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| 88 | 1.000, 0.998, 0.997, 0.996, 0.995, 0.994, 0.992, 0.990, |
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| 89 | 0.970, 0.950, 0.920, 0.890, 0.850, 0.800, 0.750, 0.700, |
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| 90 | 0.600, 0.500, 0.400, 0.300, 0.200, 0.100, 0.050 |
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| 91 | }; |
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| 92 | |
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| 93 | |
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| 94 | //----------------------------------------------------------------------------- |
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| 95 | G4double G4MuonNucleusInteractionModel::computeMicroscopicCrossSection |
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| 96 | (const G4Track &muonTrack) |
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| 97 | //----------------------------------------------------------------------------- |
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| 98 | { |
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| 99 | const G4DynamicParticle *muonDynamics = muonTrack.GetDynamicParticle(); |
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| 100 | G4double kineticEnergy = muonDynamics->GetKineticEnergy(); |
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| 101 | G4double muonMass = muonDynamics->GetDefinition()->GetPDGMass(); |
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| 102 | |
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| 103 | G4double totalEnergy = kineticEnergy + muonMass; |
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| 104 | |
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| 105 | G4double microscopicCrossSection; |
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| 106 | if(totalEnergy <= 30.0*GeV) { |
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| 107 | microscopicCrossSection |
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| 108 | = 0.0003*millibarn; |
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| 109 | } else { |
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| 110 | microscopicCrossSection |
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| 111 | = 0.0003*std::pow((totalEnergy/(30.0*GeV)), 0.25)*millibarn; |
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| 112 | } |
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| 113 | |
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| 114 | return microscopicCrossSection; |
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| 115 | } |
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| 116 | |
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| 117 | |
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| 118 | //----------------------------------------------------------------------------- |
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| 119 | void G4MuonNucleusInteractionModel::makePhysicsVector() |
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| 120 | //----------------------------------------------------------------------------- |
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| 121 | { |
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| 122 | G4double Ei, Ef; // initial and final energy of incident muon; |
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| 123 | G4double muonMass = G4MuonMinus::MuonMinus()->GetPDGMass(); |
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| 124 | |
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| 125 | for (G4int i=0; i<=(Nbin-1); i++) |
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| 126 | { |
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| 127 | G4double totalCrossSection = 0.0; |
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| 128 | Ei = theCoefficientVector->GetLowEdgeEnergy(i) + muonMass; |
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| 129 | for (G4int j=1; j<=34; j++) |
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| 130 | { |
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| 131 | cosTheta = 0.5 * (tetal[j] + tetal[j-1]); |
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| 132 | for (G4int k=1; k<=22; k++) |
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| 133 | { |
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| 134 | Ef = 0.5 * Ei * (xeml[k]+xeml[k-1]); |
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| 135 | G4double dsigma = computeDifferentialCrossSection(Ei,Ef,cosTheta); |
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| 136 | totalCrossSection = totalCrossSection |
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| 137 | + Ei * (tetal[j-1]-tetal[j])*(xeml[k-1]-xeml[k]) * dsigma; |
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| 138 | } |
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| 139 | } |
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| 140 | theCoefficientVector->PutValue(i, totalCrossSection); |
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| 141 | } |
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| 142 | } |
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| 143 | |
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| 144 | |
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| 145 | //----------------------------------------------------------------------------- |
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| 146 | G4VParticleChange* G4MuonNucleusInteractionModel::applyInteractionModel |
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| 147 | (const G4Track &muonTrack, G4Nucleus &targetNucleus ) |
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| 148 | //----------------------------------------------------------------------------- |
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| 149 | { |
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| 150 | G4int icos=0, ie1=0; |
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| 151 | G4double E1=0., P1=0.; |
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| 152 | G4double rndm[3]; |
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| 153 | G4bool isOutRange; |
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| 154 | |
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| 155 | // Initialization |
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| 156 | aParticleChange.Initialize(muonTrack); |
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| 157 | |
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| 158 | const G4DynamicParticle *muonDynamics = muonTrack.GetDynamicParticle(); |
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| 159 | G4double kineticEnergy = muonDynamics->GetKineticEnergy(); |
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| 160 | G4double totalMomentum = muonDynamics->GetTotalMomentum(); |
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| 161 | G4double totalEnergy = muonDynamics->GetTotalEnergy(); |
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| 162 | G4double muonMass = muonDynamics->GetDefinition()->GetPDGMass(); |
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| 163 | |
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| 164 | |
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| 165 | G4double W2 = 0.0; G4int W2try = 0; |
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| 166 | while (W2 <= 0.0) |
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| 167 | { |
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| 168 | G4double totalCrossSection = 0.0; |
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| 169 | G4bool interpolated = false; |
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| 170 | G4double fRndm = G4UniformRand(); |
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| 171 | G4double Hmax |
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| 172 | = theCoefficientVector->GetValue(kineticEnergy, isOutRange); |
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| 173 | for (G4int i=1; i<=34; i++) |
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| 174 | { |
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| 175 | cosTheta = 0.5 * (tetal[i] + tetal[i-1]); |
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| 176 | for (G4int j=1; j<=22; j++) |
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| 177 | { |
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| 178 | E1 = 0.5 * totalEnergy * (xeml[j]+xeml[j-1]); |
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| 179 | G4double dsigma |
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| 180 | = computeDifferentialCrossSection(totalEnergy, E1, cosTheta); |
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| 181 | totalCrossSection = totalCrossSection |
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| 182 | + totalEnergy*(tetal[i-1]-tetal[i])*(xeml[j-1]-xeml[j])*dsigma; |
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| 183 | |
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| 184 | if((fRndm*Hmax)<totalCrossSection) { |
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| 185 | interpolated = true; |
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| 186 | icos = i; ie1 = j; |
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| 187 | break; |
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| 188 | } |
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| 189 | } |
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| 190 | |
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| 191 | if(interpolated) { |
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| 192 | // calculate energy, momentum and angle of outgoing muon |
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| 193 | CLHEP::RandFlat::shootArray(3, rndm); |
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| 194 | G4double theta = std::acos(tetal[icos-1]) |
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| 195 | + rndm[0]*(std::acos(tetal[icos])-std::acos(tetal[icos-1])); |
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| 196 | cosTheta = std::cos(theta); |
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| 197 | E1 = (xeml[ie1] + rndm[1]*(xeml[ie1-1]-xeml[ie1])) * totalEnergy; |
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| 198 | if(E1<muonMass) E1 = muonMass + 0.0001*GeV; |
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| 199 | P1 = std::sqrt(std::abs(E1*E1-muonMass*muonMass)); |
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| 200 | |
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| 201 | // invariant mass of final hadron state must be greater than zero |
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| 202 | W2 = proton_mass_c2*proton_mass_c2 |
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| 203 | +2.0*proton_mass_c2*(totalEnergy-E1) |
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| 204 | -2.0*(totalEnergy*E1-totalMomentum*P1*cosTheta-muonMass*muonMass); |
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| 205 | |
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| 206 | break; |
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| 207 | } |
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| 208 | } |
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| 209 | |
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| 210 | W2try++; |
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| 211 | if (W2try>100) return &aParticleChange; |
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| 212 | } |
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| 213 | |
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| 214 | // calculate momentum of outgoing muon / pion(photon) |
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| 215 | G4double sinTheta = std::sqrt(std::abs(1.0 - cosTheta*cosTheta)); |
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| 216 | G4double phi = rndm[2]*twopi; |
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| 217 | G4ThreeVector muonDirection(sinTheta*std::cos(phi),sinTheta*std::sin(phi),cosTheta); |
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| 218 | G4ThreeVector muonDirectionInit = muonTrack.GetMomentumDirection(); |
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| 219 | muonDirection.rotateUz(muonDirectionInit); |
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| 220 | |
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| 221 | G4ParticleMomentum pionMomentum |
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| 222 | = muonDynamics->GetMomentum() - P1*muonDirection; |
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| 223 | G4double muonKineticEnergy |
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| 224 | = std::sqrt(P1*P1 + muonMass*muonMass) - muonMass; |
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| 225 | aParticleChange.ProposeMomentumDirection(muonDirection); |
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| 226 | aParticleChange.ProposeEnergy(muonKineticEnergy); |
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| 227 | aParticleChange.ProposeTrackStatus(fAlive); |
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| 228 | |
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| 229 | |
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| 230 | // virtual photon is exchanged with a pion of same Q2 |
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| 231 | // select pi+/pi- randomly and generate pion track |
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| 232 | G4ParticleDefinition* pdPion; |
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| 233 | if(CLHEP::RandBit::shootBit()) |
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| 234 | pdPion = G4PionMinus::PionMinusDefinition(); |
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| 235 | else |
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| 236 | pdPion = G4PionPlus::PionPlusDefinition(); |
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| 237 | |
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| 238 | G4DynamicParticle* pionDynamics |
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| 239 | = new G4DynamicParticle(pdPion, pionMomentum); |
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| 240 | |
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| 241 | G4Track* pionTrack = new G4Track(pionDynamics, |
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| 242 | muonTrack.GetGlobalTime(), |
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| 243 | muonTrack.GetPosition() ); |
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| 244 | pionTrack->SetStep(muonTrack.GetStep()); |
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| 245 | |
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| 246 | // Invoke pion-nucleus inelastic process |
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| 247 | invokePionNucleus(*pionTrack, targetNucleus); |
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| 248 | |
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| 249 | // Termination |
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| 250 | delete pionTrack; |
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| 251 | |
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| 252 | return &aParticleChange; |
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| 253 | } |
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| 254 | |
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| 255 | |
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| 256 | //----------------------------------------------------------------------------- |
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| 257 | void G4MuonNucleusInteractionModel::invokePionNucleus |
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| 258 | (const G4Track &pionTrack, G4Nucleus &targetNucleus ) |
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| 259 | //----------------------------------------------------------------------------- |
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| 260 | { |
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| 261 | // force interaction of pion with target nucleus |
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| 262 | G4double pionKineticEnergy = pionTrack.GetKineticEnergy(); |
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| 263 | if(pionTrack.GetDefinition()->GetParticleName() == "pi-") { |
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| 264 | if(pionKineticEnergy <= cascadeModelMarginalEnergy) |
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| 265 | pionChange |
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| 266 | = LEPionMinusInelastic->ApplyYourself(pionTrack, targetNucleus); |
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| 267 | else |
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| 268 | pionChange |
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| 269 | = HEPionMinusInelastic->ApplyYourself(pionTrack, targetNucleus); |
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| 270 | } else if(pionTrack.GetDefinition()->GetParticleName() == "pi+") { |
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| 271 | if(pionKineticEnergy <= cascadeModelMarginalEnergy) |
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| 272 | pionChange |
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| 273 | = LEPionPlusInelastic->ApplyYourself(pionTrack, targetNucleus); |
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| 274 | else |
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| 275 | pionChange |
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| 276 | = HEPionPlusInelastic->ApplyYourself(pionTrack, targetNucleus); |
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| 277 | } |
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| 278 | |
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| 279 | |
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| 280 | // add local energy deposit |
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| 281 | G4double localEnergyDeposited = 0.0; |
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| 282 | localEnergyDeposited = pionChange->GetLocalEnergyDeposit(); |
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| 283 | aParticleChange.ProposeLocalEnergyDeposit(localEnergyDeposited); |
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| 284 | |
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| 285 | |
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| 286 | // register secondary particles |
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| 287 | G4int numSecondaries = pionChange->GetNumberOfSecondaries(); |
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| 288 | aParticleChange.SetNumberOfSecondaries(numSecondaries); |
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| 289 | |
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| 290 | G4ParticleMomentum secondaryMomentum = G4ThreeVector(0.,0.,0.); |
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| 291 | for(G4int iS=0; iS<=(numSecondaries-1); iS++) { |
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| 292 | secondaryMomentum |
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| 293 | = secondaryMomentum + pionChange->GetSecondary(iS)->GetParticle()->GetMomentum(); |
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| 294 | aParticleChange.AddSecondary(pionChange->GetSecondary(iS)->GetParticle()); |
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| 295 | } |
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| 296 | pionChange->Clear(); |
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| 297 | |
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| 298 | return; |
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| 299 | } |
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| 300 | |
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| 301 | |
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| 302 | //----------------------------------------------------------------------------- |
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| 303 | G4double G4MuonNucleusInteractionModel::computeDifferentialCrossSection |
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| 304 | (G4double initialEnergy, G4double finalEnergy, G4double aCosTheta) |
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| 305 | //----------------------------------------------------------------------------- |
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| 306 | { |
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| 307 | G4double muonMass = G4MuonMinus::MuonMinus()->GetPDGMass(); |
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| 308 | |
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| 309 | if(finalEnergy < muonMass) return(0.0); |
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| 310 | if(aCosTheta >= 1.0) return DBL_MAX; |
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| 311 | |
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| 312 | G4double initialMomentum |
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| 313 | = std::sqrt(initialEnergy*initialEnergy - muonMass*muonMass); |
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| 314 | G4double finalMomentum |
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| 315 | = std::sqrt(finalEnergy*finalEnergy - muonMass*muonMass); |
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| 316 | |
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| 317 | |
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| 318 | // calculate momentum transfer (Q2) |
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| 319 | // and invariant mass of final state of hadrons (W2) |
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| 320 | G4double Q2 |
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| 321 | = 2.0*(initialEnergy*finalEnergy |
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| 322 | -initialMomentum*finalMomentum*aCosTheta-muonMass*muonMass); |
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| 323 | if(Q2 < 0.0) return(0.0); |
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| 324 | |
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| 325 | G4double W2 |
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| 326 | = proton_mass_c2*proton_mass_c2 |
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| 327 | +2.0*proton_mass_c2*(initialEnergy-finalEnergy)-Q2; |
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| 328 | if(W2 < 0.0) return(0.0); |
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| 329 | |
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| 330 | |
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| 331 | // calculate factors |
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| 332 | // Nu : energy transfer |
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| 333 | // K : incident flux of photon |
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| 334 | // Epsilon : virtual photon polarization |
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| 335 | G4double fNu = initialEnergy-finalEnergy; |
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| 336 | G4double fK = fNu+Q2/(2.0*fNu); |
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| 337 | G4double fEpsilon |
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| 338 | = 1.0/(1.0+2.0*((1.0-aCosTheta)/(1.0+aCosTheta))*(Q2+fNu*fNu)/Q2); |
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| 339 | if(fEpsilon > 1.0) return DBL_MAX; |
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| 340 | |
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| 341 | |
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| 342 | // calculate photoabsorption cross sections |
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| 343 | // fGamma : flux of transverse photons |
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| 344 | // sigma_t : for transverse photons |
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| 345 | // sigma_l : for longitudinal photons |
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| 346 | G4double fGamma |
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| 347 | = fine_structure_const*fK*finalEnergy |
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| 348 | / (pi*Q2*initialEnergy*(1.0 - fEpsilon)); |
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| 349 | G4double sigma_t = 0.12*millibarn; |
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| 350 | G4double sigma_l = 0.3*(1.0-Q2/(1.868*GeV*fNu))*sigma_t; |
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| 351 | if(sigma_l < 0.) sigma_l = 0.; |
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| 352 | |
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| 353 | return fGamma*(sigma_t+fEpsilon*sigma_l); |
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| 354 | } |
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