[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 | // Hadronic Process: Nuclear De-excitations |
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| 28 | // by V. Lara |
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| 29 | |
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| 30 | |
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| 31 | #include "G4FermiPhaseSpaceDecay.hh" |
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| 32 | #include "G4HadronicException.hh" |
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| 33 | #include "Randomize.hh" |
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| 34 | |
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| 35 | #include <algorithm> |
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| 36 | #include <numeric> |
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| 37 | #include <functional> |
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| 38 | |
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| 39 | |
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| 40 | std::vector<G4LorentzVector*> * |
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| 41 | G4FermiPhaseSpaceDecay::KopylovNBodyDecay(const G4double M, const std::vector<G4double>& m) const |
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| 42 | // Calculates momentum for N fragments (Kopylov's method of sampling is used) |
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| 43 | { |
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| 44 | G4int N = m.size(); |
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| 45 | |
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| 46 | std::vector<G4LorentzVector*>* P = new std::vector<G4LorentzVector*>; |
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| 47 | P->insert(P->begin(), N, static_cast<G4LorentzVector*>(0)); |
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| 48 | |
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| 49 | G4double mtot = std::accumulate( m.begin(), m.end(), 0.0); |
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| 50 | G4double mu = mtot; |
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| 51 | G4double PFragMagCM = 0.0; |
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| 52 | G4double Mass = M; |
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| 53 | G4double T = M-mtot; |
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| 54 | G4LorentzVector PFragCM(0.0,0.0,0.0,0.0); |
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| 55 | G4LorentzVector PFragLab(0.0,0.0,0.0,0.0); |
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| 56 | G4LorentzVector PRestCM(0.0,0.0,0.0,0.0); |
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| 57 | G4LorentzVector PRestLab(0.0,0.0,0.0,Mass); |
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| 58 | |
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| 59 | for (G4int k = N-1; k > 0; k--) |
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| 60 | { |
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| 61 | mu -= m[k]; |
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| 62 | if (k>1) T *= BetaKopylov(k); |
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| 63 | else T = 0.0; |
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| 64 | |
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| 65 | G4double RestMass = mu + T; |
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| 66 | |
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| 67 | PFragMagCM = PtwoBody(Mass,m[k],RestMass); |
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| 68 | if (PFragMagCM < 0) |
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| 69 | { |
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| 70 | throw G4HadronicException(__FILE__, __LINE__, "G4FermiPhaseSpaceDecay::KopylovNBodyDecay: Error sampling fragments momenta!!"); |
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| 71 | } |
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| 72 | |
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| 73 | |
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| 74 | // Create a unit vector with a random direction isotropically distributed |
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| 75 | G4ParticleMomentum RandVector(IsotropicVector(PFragMagCM)); |
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| 76 | |
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| 77 | PFragCM.setVect(RandVector); |
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| 78 | PFragCM.setE(std::sqrt(RandVector.mag2()+m[k]*m[k])); |
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| 79 | |
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| 80 | PRestCM.setVect(-RandVector); |
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| 81 | PRestCM.setE(std::sqrt(RandVector.mag2()+RestMass*RestMass)); |
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| 82 | |
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| 83 | |
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| 84 | G4ThreeVector BoostV = PRestLab.boostVector(); |
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| 85 | |
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| 86 | PFragLab = PFragCM; |
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| 87 | PFragLab.boost(BoostV); |
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| 88 | PRestLab = PRestCM; |
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| 89 | PRestLab.boost(BoostV); |
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| 90 | |
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| 91 | P->operator[](k) = new G4LorentzVector(PFragLab); |
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| 92 | |
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| 93 | Mass = RestMass; |
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| 94 | } |
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| 95 | |
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| 96 | P->operator[](0) = new G4LorentzVector(PRestLab); |
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| 97 | |
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| 98 | return P; |
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| 99 | |
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| 100 | } |
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| 101 | |
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| 102 | |
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| 103 | |
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| 104 | std::vector<G4LorentzVector*> * |
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| 105 | G4FermiPhaseSpaceDecay::NBodyDecay(const G4double M, const std::vector<G4double>& m) const |
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| 106 | { |
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| 107 | // Number of fragments |
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| 108 | G4int N = m.size(); |
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| 109 | G4int i, j; |
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| 110 | // Total Daughters Mass |
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| 111 | G4double mtot = std::accumulate( m.begin(), m.end(), 0.0); |
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| 112 | G4double Emax = M - mtot + m[0]; |
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| 113 | G4double Emin = 0.0; |
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| 114 | G4double Wmax = 1.0; |
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| 115 | for (i = 1; i < N; i++) |
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| 116 | { |
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| 117 | Emax += m[i]; |
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| 118 | Emin += m[i-1]; |
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| 119 | Wmax *= this->PtwoBody(Emax, Emin, m[i]); |
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| 120 | } |
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| 121 | |
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| 122 | G4int ntries = 0; |
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| 123 | G4double weight = 1.0; |
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| 124 | std::vector<G4double> p(N); |
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| 125 | do |
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| 126 | { |
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| 127 | // Sample uniform random numbers in increasing order |
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| 128 | std::vector<G4double> r; |
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| 129 | r.reserve(N); |
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| 130 | r.push_back(0.0); |
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| 131 | for (i = 1; i < N-1; i++) r.push_back(G4UniformRand()); |
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| 132 | r.push_back(1.0); |
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| 133 | std::sort(r.begin(),r.end(), std::less<G4double>()); |
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| 134 | |
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| 135 | // Calculate virtual masses |
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| 136 | std::vector<G4double> vm(N); |
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| 137 | vm[0] = 0.0; |
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| 138 | std::partial_sum(m.begin(), m.end(), vm.begin()); |
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| 139 | std::transform(r.begin(), r.end(), r.begin(), std::bind2nd(std::multiplies<G4double>(), M-mtot)); |
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| 140 | std::transform(r.begin(), r.end(), vm.begin(), vm.begin(), std::plus<G4double>()); |
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| 141 | r.clear(); |
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| 142 | |
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| 143 | // Calcualte daughter momenta |
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| 144 | weight = 1.0; |
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| 145 | for (j = 0; j < N-1; j++) |
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| 146 | { |
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| 147 | p[j] = PtwoBody(vm[j+1],vm[j],m[j+1]); |
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| 148 | if (p[j] < 0.0) |
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| 149 | { |
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| 150 | G4cerr << "G4FermiPhaseSpaceDecay::Decay: Daughter momentum less than zero\n"; |
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| 151 | weight = 0.0; |
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| 152 | break; |
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| 153 | } |
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| 154 | else |
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| 155 | { |
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| 156 | weight *= p[j]; |
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| 157 | } |
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| 158 | } |
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| 159 | p[N-1] = PtwoBody(vm[N-2], m[N-2], m[N-1]); |
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| 160 | |
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| 161 | |
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| 162 | if (ntries++ > 1000000) |
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| 163 | { |
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| 164 | throw G4HadronicException(__FILE__, __LINE__, "G4FermiPhaseSpaceDecay::Decay: Cannot determine decay kinematics"); |
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| 165 | } |
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| 166 | } |
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| 167 | while ( weight < G4UniformRand()*Wmax ); |
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| 168 | |
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| 169 | std::vector<G4LorentzVector*> * P = new std::vector<G4LorentzVector*>; |
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| 170 | P->insert(P->begin(),N, static_cast<G4LorentzVector*>(0)); |
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| 171 | |
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| 172 | G4ParticleMomentum a3P = this->IsotropicVector(p[0]); |
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| 173 | |
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| 174 | P->operator[](0) = new G4LorentzVector( a3P, std::sqrt(a3P.mag2()+m[0]*m[0]) ); |
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| 175 | P->operator[](1) = new G4LorentzVector(-a3P, std::sqrt(a3P.mag2()+m[1]*m[1]) ); |
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| 176 | for (i = 2; i < N; i++) |
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| 177 | { |
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| 178 | a3P = this->IsotropicVector(p[i-1]); |
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| 179 | P->operator[](i) = new G4LorentzVector(a3P, std::sqrt(a3P.mag2() + m[i]*m[i])); |
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| 180 | G4ThreeVector Beta = (-1.0)*P->operator[](i)->boostVector(); |
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| 181 | // boost already created particles |
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| 182 | for (j = 0; j < i; j++) |
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| 183 | { |
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| 184 | P->operator[](j)->boost(Beta); |
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| 185 | } |
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| 186 | } |
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| 187 | |
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| 188 | return P; |
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| 189 | } |
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| 190 | |
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| 191 | |
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| 192 | |
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| 193 | |
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| 194 | std::vector<G4LorentzVector*> * |
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| 195 | G4FermiPhaseSpaceDecay:: |
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| 196 | TwoBodyDecay(const G4double M, const std::vector<G4double>& m) const |
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| 197 | { |
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| 198 | G4double m0 = m.front(); |
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| 199 | G4double m1 = m.back(); |
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| 200 | G4double psqr = this->PtwoBody(M,m0,m1); |
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| 201 | G4ParticleMomentum p = this->IsotropicVector(std::sqrt(psqr)); |
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| 202 | |
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| 203 | G4LorentzVector * P41 = new G4LorentzVector; |
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| 204 | P41->setVect(p); |
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| 205 | P41->setE(std::sqrt(psqr+m0*m0)); |
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| 206 | |
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| 207 | G4LorentzVector * P42 = new G4LorentzVector; |
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| 208 | P42->setVect(-p); |
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| 209 | P42->setE(std::sqrt(psqr+m1*m1)); |
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| 210 | |
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| 211 | std::vector<G4LorentzVector*> * result = new std::vector<G4LorentzVector*>; |
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| 212 | result->push_back(P41); |
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| 213 | result->push_back(P42); |
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| 214 | return result; |
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| 215 | } |
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| 216 | |
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| 217 | |
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| 218 | |
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| 219 | |
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| 220 | G4ParticleMomentum G4FermiPhaseSpaceDecay::IsotropicVector(const G4double Magnitude) const |
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| 221 | // Samples a isotropic random vectorwith a magnitud given by Magnitude. |
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| 222 | // By default Magnitude = 1.0 |
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| 223 | { |
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| 224 | G4double CosTheta = 1.0 - 2.0*G4UniformRand(); |
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| 225 | G4double SinTheta = std::sqrt(1.0 - CosTheta*CosTheta); |
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| 226 | G4double Phi = twopi*G4UniformRand(); |
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| 227 | G4ParticleMomentum Vector(Magnitude*std::cos(Phi)*SinTheta, |
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| 228 | Magnitude*std::sin(Phi)*SinTheta, |
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| 229 | Magnitude*CosTheta); |
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| 230 | return Vector; |
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| 231 | } |
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| 232 | |
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| 233 | |
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