| Geant4 Cross Reference |
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25 //
26 //
27 // Multibody "phase space" generator, which provides multiple algorithms
28 // for sampling. Momentum vectors are generated in the center-of-mass
29 // frame of the decay, and returned in a user-supplied buffer. A sampling
30 // algorithm is specified via constructor argument.
31 //
32 // Author: Michael Kelsey (SLAC) <kelsey@slac.stanford.edu>
33
34 #include "G4HadDecayGenerator.hh"
35 #include "G4VHadDecayAlgorithm.hh"
36 #include "G4HadPhaseSpaceKopylov.hh"
37 #include "G4HadPhaseSpaceGenbod.hh"
38 #include "G4HadPhaseSpaceNBodyAsai.hh"
39 #include "G4HadronicException.hh"
40 #include "G4LorentzVector.hh"
41 #include "G4ParticleDefinition.hh"
42 #include "G4PhysicalConstants.hh"
43 #include "G4SystemOfUnits.hh"
44 #include "G4ThreeVector.hh"
45 #include "Randomize.hh"
46 #include <vector>
47 #include <algorithm>
48 #include <numeric>
49 #include <iterator>
50 #include <iostream>
51
52
53 // Constructors and destructor
54
55 G4HadDecayGenerator::G4HadDecayGenerator(Algorithm alg, G4int verbose)
56 : verboseLevel(verbose), theAlgorithm(0) {
57 switch (alg) {
58 case Kopylov: theAlgorithm = new G4HadPhaseSpaceKopylov(verboseLevel); break;
59 case GENBOD: theAlgorithm = new G4HadPhaseSpaceGenbod(verboseLevel); break;
60 case NBody: theAlgorithm = new G4HadPhaseSpaceNBodyAsai(verboseLevel); break;
61 case NONE: theAlgorithm = 0; break; // User may explicitly set no algorithm
62 default: ReportInvalidAlgorithm(alg);
63 }
64
65 if (verboseLevel) {
66 G4cout << " >>> G4HadDecayGenerator";
67 if (theAlgorithm) G4cout << " using " << theAlgorithm->GetName();
68 G4cout << G4endl;
69 }
70 }
71
72 G4HadDecayGenerator::G4HadDecayGenerator(G4VHadDecayAlgorithm* alg,
73 G4int verbose)
74 : verboseLevel(verbose), theAlgorithm(alg) {
75 if (verboseLevel) {
76 G4cout << " >>> G4HadDecayGenerator";
77 if (theAlgorithm) G4cout << " using " << theAlgorithm->GetName();
78 G4cout << G4endl;
79 }
80 }
81
82 G4HadDecayGenerator::~G4HadDecayGenerator() {
83 delete theAlgorithm;
84 theAlgorithm = 0;
85 }
86
87
88 // Sanity checks -- throws exception if no algorithm chosen
89
90 void G4HadDecayGenerator::ReportInvalidAlgorithm(Algorithm alg) const {
91 if (verboseLevel)
92 G4cerr << "G4HadDecayGenerator: bad algorithm code " << alg << G4endl;
93
94 throw G4HadronicException(__FILE__, __LINE__, "Invalid algorithm code");
95 }
96
97 void G4HadDecayGenerator::ReportMissingAlgorithm() const {
98 if (verboseLevel)
99 G4cerr << "G4HadDecayGenerator: no algorithm specified" << G4endl;
100
101 throw G4HadronicException(__FILE__, __LINE__, "Null algorithm pointer");
102 }
103
104
105 // Enable (or disable if 0) diagnostic messages
106 void G4HadDecayGenerator::SetVerboseLevel(G4int verbose) {
107 verboseLevel = verbose;
108 if (theAlgorithm) theAlgorithm->SetVerboseLevel(verbose);
109 }
110
111 const G4String& G4HadDecayGenerator::GetAlgorithmName() const {
112 static const G4String& none = "NONE";
113 return (theAlgorithm ? theAlgorithm->GetName() : none);
114 }
115
116
117 // Initial state (rest mass) and list of final masses
118
119 G4bool
120 G4HadDecayGenerator::Generate(G4double initialMass,
121 const std::vector<G4double>& masses,
122 std::vector<G4LorentzVector>& finalState) {
123 if (verboseLevel)
124 G4cout << " >>> G4HadDecayGenerator::Generate (mass)" << G4endl;
125
126 if (!theAlgorithm) ReportMissingAlgorithm();
127
128 if (masses.size() == 1U)
129 return GenerateOneBody(initialMass, masses, finalState);
130
131 theAlgorithm->Generate(initialMass, masses, finalState);
132 return !finalState.empty(); // Generator failure returns empty state
133 }
134
135 // Initial state particle and list of final masses
136
137 G4bool
138 G4HadDecayGenerator::Generate(const G4ParticleDefinition* initialPD,
139 const std::vector<G4double>& masses,
140 std::vector<G4LorentzVector>& finalState) {
141 if (verboseLevel)
142 G4cout << " >>> G4HadDecayGenerator::Generate (particle)" << G4endl;
143
144 return (initialPD && Generate(initialPD->GetPDGMass(), masses, finalState));
145 }
146
147 // Final state particles will be boosted to initial-state frame
148
149 G4bool
150 G4HadDecayGenerator::Generate(const G4LorentzVector& initialState,
151 const std::vector<G4double>& masses,
152 std::vector<G4LorentzVector>& finalState) {
153 if (verboseLevel)
154 G4cout << " >>> G4HadDecayGenerator::Generate (frame)" << G4endl;
155
156 G4bool good = Generate(initialState.m(), masses, finalState);
157 if (good) {
158 G4ThreeVector bv = initialState.boostVector();
159 for (size_t i=0; i<finalState.size(); i++) {
160 finalState[i].boost(bv);
161 }
162 }
163
164 return good;
165 }
166
167
168 // Handle special case of "one body decay" (used for kaon mixing)
169
170 G4bool G4HadDecayGenerator::
171 GenerateOneBody(G4double initialMass,
172 const std::vector<G4double>& masses,
173 std::vector<G4LorentzVector>& finalState) const {
174 if (verboseLevel>1)
175 G4cout << " >>> G4HadDecayGenerator::GenerateOneBody" << G4endl;
176
177 // Initialization and sanity checks
178 finalState.clear();
179
180 if (masses.size() != 1U) return false; // Should not have been called
181 if (std::fabs(initialMass-masses[0]) > eV) return false;
182
183 if (verboseLevel>2) G4cout << " finalState mass = " << masses[0] << G4endl;
184
185 finalState.push_back(G4LorentzVector(0.,0.,0.,masses[0]));
186 return true;
187 }
188