| Geant4 Cross Reference |
1 // 1 //
2 // ******************************************* 2 // ********************************************************************
3 // * License and Disclaimer 3 // * License and Disclaimer *
4 // * 4 // * *
5 // * The Geant4 software is copyright of th 5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided 6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License 7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/ 8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. 9 // * include a list of copyright holders. *
10 // * 10 // * *
11 // * Neither the authors of this software syst 11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing fin 12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warran 13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assum 14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file 15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitatio 16 // * for the full disclaimer and the limitation of liability. *
17 // * 17 // * *
18 // * This code implementation is the result 18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboratio 19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distri 20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you ag 21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publicati 22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Sof 23 // * acceptance of all terms of the Geant4 Software license. *
24 // ******************************************* 24 // ********************************************************************
25 // 25 //
26 // 26 //
27 // Multibody "phase space" generator using GEN 27 // Multibody "phase space" generator using GENBOD (CERNLIB W515) method.
28 // 28 //
29 // Author: Michael Kelsey (SLAC) <kelsey@slac 29 // Author: Michael Kelsey (SLAC) <kelsey@slac.stanford.edu>
30 30
31 #include "G4HadPhaseSpaceGenbod.hh" 31 #include "G4HadPhaseSpaceGenbod.hh"
32 #include "G4LorentzVector.hh" 32 #include "G4LorentzVector.hh"
33 #include "G4PhysicalConstants.hh" 33 #include "G4PhysicalConstants.hh"
34 #include "G4ThreeVector.hh" 34 #include "G4ThreeVector.hh"
35 #include "Randomize.hh" 35 #include "Randomize.hh"
36 #include <algorithm> 36 #include <algorithm>
37 #include <functional> 37 #include <functional>
38 #include <iterator> 38 #include <iterator>
39 #include <numeric> 39 #include <numeric>
40 #include <vector> 40 #include <vector>
41 41
42 42
43 namespace { 43 namespace {
44 // Wrap #define in a true function, for pass 44 // Wrap #define in a true function, for passing to std::fill
45 G4double uniformRand() { return G4UniformRan 45 G4double uniformRand() { return G4UniformRand(); }
46 } 46 }
47 47
48 48
49 // Constructor initializes everything to zero 49 // Constructor initializes everything to zero
50 50
51 G4HadPhaseSpaceGenbod::G4HadPhaseSpaceGenbod(G 51 G4HadPhaseSpaceGenbod::G4HadPhaseSpaceGenbod(G4int verbose)
52 : G4VHadPhaseSpaceAlgorithm("G4HadPhaseSpace 52 : G4VHadPhaseSpaceAlgorithm("G4HadPhaseSpaceGenbod",verbose),
53 nFinal(0), totalMass(0.), massExcess(0.), 53 nFinal(0), totalMass(0.), massExcess(0.), weightMax(0.), nTrials(0) {;}
54 54
55 55
56 // C++ re-implementation of GENBOD.F (Raubold- 56 // C++ re-implementation of GENBOD.F (Raubold-Lynch method)
57 57
58 void G4HadPhaseSpaceGenbod:: 58 void G4HadPhaseSpaceGenbod::
59 GenerateMultiBody(G4double initialMass, 59 GenerateMultiBody(G4double initialMass,
60 const std::vector<G4double>& masses, 60 const std::vector<G4double>& masses,
61 std::vector<G4LorentzVector>& finalState 61 std::vector<G4LorentzVector>& finalState) {
62 if (GetVerboseLevel()) G4cout << GetName() < 62 if (GetVerboseLevel()) G4cout << GetName() << "::GenerateMultiBody" << G4endl;
63 63
64 finalState.clear(); 64 finalState.clear();
65 65
66 Initialize(initialMass, masses); 66 Initialize(initialMass, masses);
67 67
68 const G4int maxNumberOfLoops = 10000; 68 const G4int maxNumberOfLoops = 10000;
69 nTrials = 0; 69 nTrials = 0;
70 do { // Apply accept/reject to get di 70 do { // Apply accept/reject to get distribution
71 ++nTrials; 71 ++nTrials;
72 FillRandomBuffer(); 72 FillRandomBuffer();
73 FillEnergySteps(initialMass, masses); 73 FillEnergySteps(initialMass, masses);
74 } while ( (!AcceptEvent()) && nTrials < maxN 74 } while ( (!AcceptEvent()) && nTrials < maxNumberOfLoops ); /* Loop checking, 02.11.2015, A.Ribon */
75 if ( nTrials >= maxNumberOfLoops ) { 75 if ( nTrials >= maxNumberOfLoops ) {
76 G4ExceptionDescription ed; 76 G4ExceptionDescription ed;
77 ed << " Failed sampling after maxNumberOfL 77 ed << " Failed sampling after maxNumberOfLoops attempts : forced exit" << G4endl;
78 G4Exception( " G4HadPhaseSpaceGenbod::Gene 78 G4Exception( " G4HadPhaseSpaceGenbod::GenerateMultiBody ", "HAD_GENBOD_001", FatalException, ed );
79 } 79 }
80 GenerateMomenta(masses, finalState); 80 GenerateMomenta(masses, finalState);
81 } 81 }
82 82
83 void G4HadPhaseSpaceGenbod:: 83 void G4HadPhaseSpaceGenbod::
84 Initialize(G4double initialMass, const std::ve 84 Initialize(G4double initialMass, const std::vector<G4double>& masses) {
85 if (GetVerboseLevel()>1) G4cout << GetName() 85 if (GetVerboseLevel()>1) G4cout << GetName() << "::Initialize" << G4endl;
86 86
87 nFinal = masses.size(); 87 nFinal = masses.size();
88 msum.resize(nFinal, 0.); // Initialize bu 88 msum.resize(nFinal, 0.); // Initialize buffers for filling
89 msq.resize(nFinal, 0.); 89 msq.resize(nFinal, 0.);
90 90
91 std::partial_sum(masses.begin(), masses.end( 91 std::partial_sum(masses.begin(), masses.end(), msum.begin());
92 std::transform(masses.begin(), masses.end(), 92 std::transform(masses.begin(), masses.end(), masses.begin(), msq.begin(),
93 std::multiplies<G4double>()); 93 std::multiplies<G4double>());
94 totalMass = msum.back(); 94 totalMass = msum.back();
95 massExcess = initialMass - totalMass; 95 massExcess = initialMass - totalMass;
96 96
97 if (GetVerboseLevel()>2) { 97 if (GetVerboseLevel()>2) {
98 PrintVector(msum, "msum", G4cout); 98 PrintVector(msum, "msum", G4cout);
99 PrintVector(msq, "msq", G4cout); 99 PrintVector(msq, "msq", G4cout);
100 G4cout << " totalMass " << totalMass << " 100 G4cout << " totalMass " << totalMass << " massExcess " << massExcess
101 << G4endl; 101 << G4endl;
102 } 102 }
103 103
104 ComputeWeightScale(masses); 104 ComputeWeightScale(masses);
105 } 105 }
106 106
107 107
108 // Generate ordered list of random numbers 108 // Generate ordered list of random numbers
109 109
110 void G4HadPhaseSpaceGenbod::FillRandomBuffer() 110 void G4HadPhaseSpaceGenbod::FillRandomBuffer() {
111 if (GetVerboseLevel()>1) G4cout << GetName() 111 if (GetVerboseLevel()>1) G4cout << GetName() << "::FillRandomBuffer" << G4endl;
112 112
113 rndm.resize(nFinal-2,0.); // Final states ge 113 rndm.resize(nFinal-2,0.); // Final states generated in sorted order
114 std::generate(rndm.begin(), rndm.end(), unif 114 std::generate(rndm.begin(), rndm.end(), uniformRand);
115 std::sort(rndm.begin(), rndm.end()); 115 std::sort(rndm.begin(), rndm.end());
116 if (GetVerboseLevel()>2) PrintVector(rndm, " 116 if (GetVerboseLevel()>2) PrintVector(rndm, "rndm", G4cout);
117 } 117 }
118 118
119 119
120 // Final state effective masses, min to max 120 // Final state effective masses, min to max
121 121
122 void 122 void
123 G4HadPhaseSpaceGenbod::FillEnergySteps(G4doubl 123 G4HadPhaseSpaceGenbod::FillEnergySteps(G4double initialMass,
124 const std::vector<G4double>& ma 124 const std::vector<G4double>& masses) {
125 if (GetVerboseLevel()>1) G4cout << GetName() 125 if (GetVerboseLevel()>1) G4cout << GetName() << "::FillEnergySteps" << G4endl;
126 126
127 meff.clear(); 127 meff.clear();
128 pd.clear(); 128 pd.clear();
129 129
130 meff.push_back(masses[0]); 130 meff.push_back(masses[0]);
131 for (size_t i=1; i<nFinal-1; i++) { 131 for (size_t i=1; i<nFinal-1; i++) {
132 meff.push_back(rndm[i-1]*massExcess + msum 132 meff.push_back(rndm[i-1]*massExcess + msum[i]);
133 pd.push_back(TwoBodyMomentum(meff[i], meff 133 pd.push_back(TwoBodyMomentum(meff[i], meff[i-1], masses[i]));
134 } 134 }
135 meff.push_back(initialMass); 135 meff.push_back(initialMass);
136 pd.push_back(TwoBodyMomentum(meff[nFinal-1], 136 pd.push_back(TwoBodyMomentum(meff[nFinal-1], meff[nFinal-2], masses[nFinal-1]));
137 137
138 if (GetVerboseLevel()>2) { 138 if (GetVerboseLevel()>2) {
139 PrintVector(meff,"meff",G4cout); 139 PrintVector(meff,"meff",G4cout);
140 PrintVector(pd,"pd",G4cout); 140 PrintVector(pd,"pd",G4cout);
141 } 141 }
142 } 142 }
143 143
144 144
145 // Maximum possible weight for final state (us 145 // Maximum possible weight for final state (used with accept/reject)
146 146
147 void 147 void
148 G4HadPhaseSpaceGenbod::ComputeWeightScale(cons 148 G4HadPhaseSpaceGenbod::ComputeWeightScale(const std::vector<G4double>& masses) {
149 if (GetVerboseLevel()>1) 149 if (GetVerboseLevel()>1)
150 G4cout << GetName() << "::ComputeWeightSca 150 G4cout << GetName() << "::ComputeWeightScale" << G4endl;
151 151
152 weightMax = 1.; 152 weightMax = 1.;
153 for (size_t i=1; i<nFinal; i++) { 153 for (size_t i=1; i<nFinal; i++) {
154 weightMax *= TwoBodyMomentum(massExcess+ms 154 weightMax *= TwoBodyMomentum(massExcess+msum[i], msum[i-1], masses[i]);
155 } 155 }
156 156
157 if (GetVerboseLevel()>2) G4cout << " weightM 157 if (GetVerboseLevel()>2) G4cout << " weightMax = " << weightMax << G4endl;
158 } 158 }
159 159
160 160
161 // Event weight computed as either constant or 161 // Event weight computed as either constant or Fermi-dependent cross-section
162 162
163 G4double G4HadPhaseSpaceGenbod::ComputeWeight( 163 G4double G4HadPhaseSpaceGenbod::ComputeWeight() const {
164 if (GetVerboseLevel()>1) G4cout << GetName() 164 if (GetVerboseLevel()>1) G4cout << GetName() << "::ComputeWeight" << G4endl;
165 165
166 return (std::accumulate(pd.begin(), pd.end() 166 return (std::accumulate(pd.begin(), pd.end(), 1./weightMax,
167 std::multiplies<G4double>())); 167 std::multiplies<G4double>()));
168 } 168 }
169 169
170 G4bool G4HadPhaseSpaceGenbod::AcceptEvent() co 170 G4bool G4HadPhaseSpaceGenbod::AcceptEvent() const {
171 if (GetVerboseLevel()>1) 171 if (GetVerboseLevel()>1)
172 G4cout << GetName() << "::AcceptEvent? " < 172 G4cout << GetName() << "::AcceptEvent? " << nTrials << G4endl;
173 173
174 return (G4UniformRand() <= ComputeWeight()); 174 return (G4UniformRand() <= ComputeWeight());
175 } 175 }
176 176
177 177
178 // Final state momentum vectors in CMS system, 178 // Final state momentum vectors in CMS system, using Raubold-Lynch method
179 179
180 void G4HadPhaseSpaceGenbod:: 180 void G4HadPhaseSpaceGenbod::
181 GenerateMomenta(const std::vector<G4double>& m 181 GenerateMomenta(const std::vector<G4double>& masses,
182 std::vector<G4LorentzVector>& finalState) 182 std::vector<G4LorentzVector>& finalState) {
183 if (GetVerboseLevel()>1) G4cout << GetName() 183 if (GetVerboseLevel()>1) G4cout << GetName() << "::GenerateMomenta" << G4endl;
184 184
185 finalState.resize(nFinal); // Preallocate v 185 finalState.resize(nFinal); // Preallocate vectors for convenience below
186 186
187 for (size_t i=0; i<nFinal; i++) { 187 for (size_t i=0; i<nFinal; i++) {
188 AccumulateFinalState(i, masses, finalState 188 AccumulateFinalState(i, masses, finalState);
189 if (GetVerboseLevel()>2) 189 if (GetVerboseLevel()>2)
190 G4cout << " finalState[" << i << "] " << 190 G4cout << " finalState[" << i << "] " << finalState[i] << G4endl;
191 } 191 }
192 } 192 }
193 193
194 // Process final state daughters up to current 194 // Process final state daughters up to current index
195 195
196 void G4HadPhaseSpaceGenbod:: 196 void G4HadPhaseSpaceGenbod::
197 AccumulateFinalState(size_t i, 197 AccumulateFinalState(size_t i,
198 const std::vector<G4double>& masses, 198 const std::vector<G4double>& masses,
199 std::vector<G4LorentzVector>& finalSt 199 std::vector<G4LorentzVector>& finalState) {
200 if (GetVerboseLevel()>2) 200 if (GetVerboseLevel()>2)
201 G4cout << GetName() << "::AccumulateFinalS 201 G4cout << GetName() << "::AccumulateFinalState " << i << G4endl;
202 202
203 if (i==0) { // First final state particl 203 if (i==0) { // First final state particle left alone
204 finalState[i].setVectM(G4ThreeVector(0.,pd 204 finalState[i].setVectM(G4ThreeVector(0.,pd[i],0.),masses[i]);
205 return; 205 return;
206 } 206 }
207 207
208 finalState[i].setVectM(G4ThreeVector(0.,-pd[ 208 finalState[i].setVectM(G4ThreeVector(0.,-pd[i-1],0.),masses[i]);
209 G4double phi = G4UniformRand() * twopi; 209 G4double phi = G4UniformRand() * twopi;
210 G4double theta = std::acos(2.*G4UniformRand( 210 G4double theta = std::acos(2.*G4UniformRand() - 1.);
211 211
212 if (GetVerboseLevel() > 2) { 212 if (GetVerboseLevel() > 2) {
213 G4cout << " initialized Py " << -pd[i-1] < 213 G4cout << " initialized Py " << -pd[i-1] << " phi " << phi
214 << " theta " << theta << G4endl; 214 << " theta " << theta << G4endl;
215 } 215 }
216 216
217 G4double esys=0.,beta=0.,gamma=1.; 217 G4double esys=0.,beta=0.,gamma=1.;
218 if (i < nFinal-1) { // Do not boost fina 218 if (i < nFinal-1) { // Do not boost final particle
219 esys = std::sqrt(pd[i]*pd[i]+meff[i]*meff[ 219 esys = std::sqrt(pd[i]*pd[i]+meff[i]*meff[i]);
220 beta = pd[i] / esys; 220 beta = pd[i] / esys;
221 gamma = esys / meff[i]; 221 gamma = esys / meff[i];
222 222
223 if (GetVerboseLevel()>2) 223 if (GetVerboseLevel()>2)
224 G4cout << " esys " << esys << " beta " < 224 G4cout << " esys " << esys << " beta " << beta << " gamma " << gamma
225 << G4endl; 225 << G4endl;
226 } 226 }
227 227
228 for (size_t j=0; j<=i; j++) { // Accumulat 228 for (size_t j=0; j<=i; j++) { // Accumulate rotations
229 finalState[j].rotateZ(theta).rotateY(phi); 229 finalState[j].rotateZ(theta).rotateY(phi);
230 finalState[j].setY(gamma*(finalState[j].y( 230 finalState[j].setY(gamma*(finalState[j].y() + beta*finalState[j].e()));
231 if (GetVerboseLevel()>2) G4cout << " j " < 231 if (GetVerboseLevel()>2) G4cout << " j " << j << " " << finalState[j] << G4endl;
232 } 232 }
233 } 233 }
234 234