[819] | 1 | // |
---|
| 2 | // ******************************************************************** |
---|
| 3 | // * License and Disclaimer * |
---|
| 4 | // * * |
---|
| 5 | // * The Geant4 software is copyright of the Copyright Holders of * |
---|
| 6 | // * the Geant4 Collaboration. It is provided under the terms and * |
---|
| 7 | // * conditions of the Geant4 Software License, included in the file * |
---|
| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
---|
| 9 | // * include a list of copyright holders. * |
---|
| 10 | // * * |
---|
| 11 | // * Neither the authors of this software system, nor their employing * |
---|
| 12 | // * institutes,nor the agencies providing financial support for this * |
---|
| 13 | // * work make any representation or warranty, express or implied, * |
---|
| 14 | // * regarding this software system or assume any liability for its * |
---|
| 15 | // * use. Please see the license in the file LICENSE and URL above * |
---|
| 16 | // * for the full disclaimer and the limitation of liability. * |
---|
| 17 | // * * |
---|
| 18 | // * This code implementation is the result of the scientific and * |
---|
| 19 | // * technical work of the GEANT4 collaboration. * |
---|
| 20 | // * By using, copying, modifying or distributing the software (or * |
---|
| 21 | // * any work based on the software) you agree to acknowledge its * |
---|
| 22 | // * use in resulting scientific publications, and indicate your * |
---|
| 23 | // * acceptance of all terms of the Geant4 Software license. * |
---|
| 24 | // ******************************************************************** |
---|
| 25 | // |
---|
| 26 | // |
---|
| 27 | // Hadronic Process: Nuclear De-excitations |
---|
| 28 | // by V. Lara |
---|
| 29 | |
---|
| 30 | |
---|
| 31 | #include "G4FermiPhaseSpaceDecay.hh" |
---|
| 32 | #include "G4HadronicException.hh" |
---|
| 33 | #include "Randomize.hh" |
---|
| 34 | |
---|
| 35 | #include <algorithm> |
---|
| 36 | #include <numeric> |
---|
| 37 | #include <functional> |
---|
| 38 | |
---|
[1315] | 39 | G4FermiPhaseSpaceDecay::G4FermiPhaseSpaceDecay() |
---|
| 40 | { |
---|
| 41 | } |
---|
[819] | 42 | |
---|
[1315] | 43 | G4FermiPhaseSpaceDecay::~G4FermiPhaseSpaceDecay() |
---|
| 44 | { |
---|
| 45 | } |
---|
| 46 | |
---|
[819] | 47 | std::vector<G4LorentzVector*> * |
---|
| 48 | G4FermiPhaseSpaceDecay::KopylovNBodyDecay(const G4double M, const std::vector<G4double>& m) const |
---|
| 49 | // Calculates momentum for N fragments (Kopylov's method of sampling is used) |
---|
| 50 | { |
---|
| 51 | G4int N = m.size(); |
---|
| 52 | |
---|
| 53 | std::vector<G4LorentzVector*>* P = new std::vector<G4LorentzVector*>; |
---|
| 54 | P->insert(P->begin(), N, static_cast<G4LorentzVector*>(0)); |
---|
| 55 | |
---|
| 56 | G4double mtot = std::accumulate( m.begin(), m.end(), 0.0); |
---|
| 57 | G4double mu = mtot; |
---|
| 58 | G4double PFragMagCM = 0.0; |
---|
| 59 | G4double Mass = M; |
---|
| 60 | G4double T = M-mtot; |
---|
| 61 | G4LorentzVector PFragCM(0.0,0.0,0.0,0.0); |
---|
| 62 | G4LorentzVector PFragLab(0.0,0.0,0.0,0.0); |
---|
| 63 | G4LorentzVector PRestCM(0.0,0.0,0.0,0.0); |
---|
| 64 | G4LorentzVector PRestLab(0.0,0.0,0.0,Mass); |
---|
| 65 | |
---|
| 66 | for (G4int k = N-1; k > 0; k--) |
---|
| 67 | { |
---|
| 68 | mu -= m[k]; |
---|
| 69 | if (k>1) T *= BetaKopylov(k); |
---|
| 70 | else T = 0.0; |
---|
| 71 | |
---|
| 72 | G4double RestMass = mu + T; |
---|
| 73 | |
---|
| 74 | PFragMagCM = PtwoBody(Mass,m[k],RestMass); |
---|
| 75 | if (PFragMagCM < 0) |
---|
| 76 | { |
---|
| 77 | throw G4HadronicException(__FILE__, __LINE__, "G4FermiPhaseSpaceDecay::KopylovNBodyDecay: Error sampling fragments momenta!!"); |
---|
| 78 | } |
---|
| 79 | |
---|
| 80 | |
---|
| 81 | // Create a unit vector with a random direction isotropically distributed |
---|
| 82 | G4ParticleMomentum RandVector(IsotropicVector(PFragMagCM)); |
---|
| 83 | |
---|
| 84 | PFragCM.setVect(RandVector); |
---|
| 85 | PFragCM.setE(std::sqrt(RandVector.mag2()+m[k]*m[k])); |
---|
| 86 | |
---|
| 87 | PRestCM.setVect(-RandVector); |
---|
| 88 | PRestCM.setE(std::sqrt(RandVector.mag2()+RestMass*RestMass)); |
---|
| 89 | |
---|
| 90 | |
---|
| 91 | G4ThreeVector BoostV = PRestLab.boostVector(); |
---|
| 92 | |
---|
| 93 | PFragLab = PFragCM; |
---|
| 94 | PFragLab.boost(BoostV); |
---|
| 95 | PRestLab = PRestCM; |
---|
| 96 | PRestLab.boost(BoostV); |
---|
| 97 | |
---|
| 98 | P->operator[](k) = new G4LorentzVector(PFragLab); |
---|
| 99 | |
---|
| 100 | Mass = RestMass; |
---|
| 101 | } |
---|
| 102 | |
---|
| 103 | P->operator[](0) = new G4LorentzVector(PRestLab); |
---|
| 104 | |
---|
| 105 | return P; |
---|
| 106 | |
---|
| 107 | } |
---|
| 108 | |
---|
| 109 | |
---|
| 110 | |
---|
| 111 | std::vector<G4LorentzVector*> * |
---|
| 112 | G4FermiPhaseSpaceDecay::NBodyDecay(const G4double M, const std::vector<G4double>& m) const |
---|
| 113 | { |
---|
| 114 | // Number of fragments |
---|
| 115 | G4int N = m.size(); |
---|
| 116 | G4int i, j; |
---|
| 117 | // Total Daughters Mass |
---|
| 118 | G4double mtot = std::accumulate( m.begin(), m.end(), 0.0); |
---|
| 119 | G4double Emax = M - mtot + m[0]; |
---|
| 120 | G4double Emin = 0.0; |
---|
| 121 | G4double Wmax = 1.0; |
---|
| 122 | for (i = 1; i < N; i++) |
---|
| 123 | { |
---|
| 124 | Emax += m[i]; |
---|
| 125 | Emin += m[i-1]; |
---|
| 126 | Wmax *= this->PtwoBody(Emax, Emin, m[i]); |
---|
| 127 | } |
---|
| 128 | |
---|
| 129 | G4int ntries = 0; |
---|
| 130 | G4double weight = 1.0; |
---|
| 131 | std::vector<G4double> p(N); |
---|
| 132 | do |
---|
| 133 | { |
---|
| 134 | // Sample uniform random numbers in increasing order |
---|
| 135 | std::vector<G4double> r; |
---|
| 136 | r.reserve(N); |
---|
| 137 | r.push_back(0.0); |
---|
| 138 | for (i = 1; i < N-1; i++) r.push_back(G4UniformRand()); |
---|
| 139 | r.push_back(1.0); |
---|
| 140 | std::sort(r.begin(),r.end(), std::less<G4double>()); |
---|
| 141 | |
---|
| 142 | // Calculate virtual masses |
---|
| 143 | std::vector<G4double> vm(N); |
---|
| 144 | vm[0] = 0.0; |
---|
| 145 | std::partial_sum(m.begin(), m.end(), vm.begin()); |
---|
| 146 | std::transform(r.begin(), r.end(), r.begin(), std::bind2nd(std::multiplies<G4double>(), M-mtot)); |
---|
| 147 | std::transform(r.begin(), r.end(), vm.begin(), vm.begin(), std::plus<G4double>()); |
---|
| 148 | r.clear(); |
---|
| 149 | |
---|
| 150 | // Calcualte daughter momenta |
---|
| 151 | weight = 1.0; |
---|
| 152 | for (j = 0; j < N-1; j++) |
---|
| 153 | { |
---|
| 154 | p[j] = PtwoBody(vm[j+1],vm[j],m[j+1]); |
---|
| 155 | if (p[j] < 0.0) |
---|
| 156 | { |
---|
| 157 | G4cerr << "G4FermiPhaseSpaceDecay::Decay: Daughter momentum less than zero\n"; |
---|
| 158 | weight = 0.0; |
---|
| 159 | break; |
---|
| 160 | } |
---|
| 161 | else |
---|
| 162 | { |
---|
| 163 | weight *= p[j]; |
---|
| 164 | } |
---|
| 165 | } |
---|
| 166 | p[N-1] = PtwoBody(vm[N-2], m[N-2], m[N-1]); |
---|
| 167 | |
---|
| 168 | |
---|
| 169 | if (ntries++ > 1000000) |
---|
| 170 | { |
---|
| 171 | throw G4HadronicException(__FILE__, __LINE__, "G4FermiPhaseSpaceDecay::Decay: Cannot determine decay kinematics"); |
---|
| 172 | } |
---|
| 173 | } |
---|
| 174 | while ( weight < G4UniformRand()*Wmax ); |
---|
| 175 | |
---|
| 176 | std::vector<G4LorentzVector*> * P = new std::vector<G4LorentzVector*>; |
---|
| 177 | P->insert(P->begin(),N, static_cast<G4LorentzVector*>(0)); |
---|
| 178 | |
---|
| 179 | G4ParticleMomentum a3P = this->IsotropicVector(p[0]); |
---|
| 180 | |
---|
| 181 | P->operator[](0) = new G4LorentzVector( a3P, std::sqrt(a3P.mag2()+m[0]*m[0]) ); |
---|
| 182 | P->operator[](1) = new G4LorentzVector(-a3P, std::sqrt(a3P.mag2()+m[1]*m[1]) ); |
---|
| 183 | for (i = 2; i < N; i++) |
---|
| 184 | { |
---|
| 185 | a3P = this->IsotropicVector(p[i-1]); |
---|
| 186 | P->operator[](i) = new G4LorentzVector(a3P, std::sqrt(a3P.mag2() + m[i]*m[i])); |
---|
| 187 | G4ThreeVector Beta = (-1.0)*P->operator[](i)->boostVector(); |
---|
| 188 | // boost already created particles |
---|
| 189 | for (j = 0; j < i; j++) |
---|
| 190 | { |
---|
| 191 | P->operator[](j)->boost(Beta); |
---|
| 192 | } |
---|
| 193 | } |
---|
| 194 | |
---|
| 195 | return P; |
---|
| 196 | } |
---|
| 197 | |
---|
| 198 | |
---|
| 199 | |
---|
| 200 | |
---|
| 201 | std::vector<G4LorentzVector*> * |
---|
| 202 | G4FermiPhaseSpaceDecay:: |
---|
| 203 | TwoBodyDecay(const G4double M, const std::vector<G4double>& m) const |
---|
| 204 | { |
---|
| 205 | G4double m0 = m.front(); |
---|
| 206 | G4double m1 = m.back(); |
---|
| 207 | G4double psqr = this->PtwoBody(M,m0,m1); |
---|
| 208 | G4ParticleMomentum p = this->IsotropicVector(std::sqrt(psqr)); |
---|
| 209 | |
---|
| 210 | G4LorentzVector * P41 = new G4LorentzVector; |
---|
| 211 | P41->setVect(p); |
---|
| 212 | P41->setE(std::sqrt(psqr+m0*m0)); |
---|
| 213 | |
---|
| 214 | G4LorentzVector * P42 = new G4LorentzVector; |
---|
| 215 | P42->setVect(-p); |
---|
| 216 | P42->setE(std::sqrt(psqr+m1*m1)); |
---|
| 217 | |
---|
| 218 | std::vector<G4LorentzVector*> * result = new std::vector<G4LorentzVector*>; |
---|
| 219 | result->push_back(P41); |
---|
| 220 | result->push_back(P42); |
---|
| 221 | return result; |
---|
| 222 | } |
---|
| 223 | |
---|
| 224 | |
---|
| 225 | |
---|
| 226 | |
---|
| 227 | G4ParticleMomentum G4FermiPhaseSpaceDecay::IsotropicVector(const G4double Magnitude) const |
---|
| 228 | // Samples a isotropic random vectorwith a magnitud given by Magnitude. |
---|
| 229 | // By default Magnitude = 1.0 |
---|
| 230 | { |
---|
| 231 | G4double CosTheta = 1.0 - 2.0*G4UniformRand(); |
---|
| 232 | G4double SinTheta = std::sqrt(1.0 - CosTheta*CosTheta); |
---|
| 233 | G4double Phi = twopi*G4UniformRand(); |
---|
| 234 | G4ParticleMomentum Vector(Magnitude*std::cos(Phi)*SinTheta, |
---|
| 235 | Magnitude*std::sin(Phi)*SinTheta, |
---|
| 236 | Magnitude*CosTheta); |
---|
| 237 | return Vector; |
---|
| 238 | } |
---|
| 239 | |
---|
| 240 | |
---|