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26 // 26 //
27 // Multibody "phase space" generator using Kop 27 // Multibody "phase space" generator using Kopylov's algorithm
28 // 28 //
29 // Author: Michael Kelsey (SLAC) <kelsey@slac 29 // Author: Michael Kelsey (SLAC) <kelsey@slac.stanford.edu>
30 30
31 #include "G4HadPhaseSpaceKopylov.hh" 31 #include "G4HadPhaseSpaceKopylov.hh"
32 #include "G4LorentzVector.hh" 32 #include "G4LorentzVector.hh"
33 #include "G4Pow.hh" 33 #include "G4Pow.hh"
34 #include "Randomize.hh" 34 #include "Randomize.hh"
35 #include <vector> 35 #include <vector>
36 #include <algorithm> 36 #include <algorithm>
37 #include <numeric> 37 #include <numeric>
38 #include <cmath> 38 #include <cmath>
39 39
40 40
41 // Generator 41 // Generator
42 42
43 void G4HadPhaseSpaceKopylov:: 43 void G4HadPhaseSpaceKopylov::
44 GenerateMultiBody(G4double initialMass, 44 GenerateMultiBody(G4double initialMass,
45 const std::vector<G4double>& masses, 45 const std::vector<G4double>& masses,
46 std::vector<G4LorentzVector>& finalState 46 std::vector<G4LorentzVector>& finalState) {
47 if (GetVerboseLevel()) G4cout << GetName() < 47 if (GetVerboseLevel()) G4cout << GetName() << "::GenerateMultiBody" << G4endl;
48 48
49 finalState.clear(); 49 finalState.clear();
50 50
51 G4int N = (G4int)masses.size(); 51 G4int N = (G4int)masses.size();
52 finalState.resize(N); 52 finalState.resize(N);
53 53
54 G4double mtot = std::accumulate(masses.begin 54 G4double mtot = std::accumulate(masses.begin(), masses.end(), 0.0);
55 G4double mu = mtot; 55 G4double mu = mtot;
56 G4double PFragMagCM = 0.0; 56 G4double PFragMagCM = 0.0;
57 G4double Mass = initialMass; 57 G4double Mass = initialMass;
58 G4double T = Mass-mtot; 58 G4double T = Mass-mtot;
59 G4LorentzVector PFragCM(0.0,0.0,0.0,0.0); 59 G4LorentzVector PFragCM(0.0,0.0,0.0,0.0);
60 G4LorentzVector PRestCM(0.0,0.0,0.0,0.0); 60 G4LorentzVector PRestCM(0.0,0.0,0.0,0.0);
61 G4LorentzVector PRestLab(0.0,0.0,0.0,Mass); 61 G4LorentzVector PRestLab(0.0,0.0,0.0,Mass);
62 62
63 for (G4int k=N-1; k>0; --k) { 63 for (G4int k=N-1; k>0; --k) {
64 mu -= masses[k]; 64 mu -= masses[k];
65 T *= (k>1) ? BetaKopylov(k) : 0.; 65 T *= (k>1) ? BetaKopylov(k) : 0.;
66 66
67 G4double RestMass = mu + T; 67 G4double RestMass = mu + T;
68 68
69 PFragMagCM = TwoBodyMomentum(Mass,masses[k 69 PFragMagCM = TwoBodyMomentum(Mass,masses[k],RestMass);
70 70
71 // Create a unit vector with a random dire 71 // Create a unit vector with a random direction isotropically distributed
72 G4ThreeVector RandVector = UniformVector(P 72 G4ThreeVector RandVector = UniformVector(PFragMagCM);
73 73
74 PFragCM.setVectM(RandVector,masses[k]); 74 PFragCM.setVectM(RandVector,masses[k]);
75 PRestCM.setVectM(-RandVector,RestMass); 75 PRestCM.setVectM(-RandVector,RestMass);
76 76
77 G4ThreeVector BoostV = PRestLab.boostVecto 77 G4ThreeVector BoostV = PRestLab.boostVector();
78 78
79 PFragCM.boost(BoostV); 79 PFragCM.boost(BoostV);
80 PRestCM.boost(BoostV); 80 PRestCM.boost(BoostV);
81 PRestLab = PRestCM; 81 PRestLab = PRestCM;
82 Mass = RestMass; 82 Mass = RestMass;
83 finalState[k] = PFragCM; 83 finalState[k] = PFragCM;
84 } 84 }
85 85
86 finalState[0] = PRestLab; 86 finalState[0] = PRestLab;
87 } 87 }
88 88
89 89
90 // Generate scale factor for final state parti 90 // Generate scale factor for final state particle
91 91
92 G4double G4HadPhaseSpaceKopylov::BetaKopylov(G 92 G4double G4HadPhaseSpaceKopylov::BetaKopylov(G4int K) const {
93 G4Pow* g4pow = G4Pow::GetInstance(); 93 G4Pow* g4pow = G4Pow::GetInstance();
94 94
95 G4int N = 3*K - 5; 95 G4int N = 3*K - 5;
96 G4double xN = G4double(N); 96 G4double xN = G4double(N);
97 G4double Fmax = std::sqrt(g4pow->powN(xN/(xN 97 G4double Fmax = std::sqrt(g4pow->powN(xN/(xN+1.),N)/(xN+1.));
98 98
99 G4double F, chi; 99 G4double F, chi;
100 const G4int maxNumberOfLoops = 10000; 100 const G4int maxNumberOfLoops = 10000;
101 G4int loopCounter = 0; 101 G4int loopCounter = 0;
102 do { 102 do {
103 chi = G4UniformRand(); 103 chi = G4UniformRand();
104 F = std::sqrt(g4pow->powN(chi,N)*(1.-chi)) 104 F = std::sqrt(g4pow->powN(chi,N)*(1.-chi));
105 } while ( ( Fmax*G4UniformRand() > F ) && ++ 105 } while ( ( Fmax*G4UniformRand() > F ) && ++loopCounter < maxNumberOfLoops ); /* Loop checking, 02.11.2015, A.Ribon */
106 if ( loopCounter >= maxNumberOfLoops ) { 106 if ( loopCounter >= maxNumberOfLoops ) {
107 G4ExceptionDescription ed; 107 G4ExceptionDescription ed;
108 ed << " Failed sampling after maxNumberOfL 108 ed << " Failed sampling after maxNumberOfLoops attempts : forced exit" << G4endl;
109 G4Exception( " G4HadPhaseSpaceKopylov::Bet 109 G4Exception( " G4HadPhaseSpaceKopylov::BetaKopylov ", "HAD_KOPYLOV_001", JustWarning, ed );
110 } 110 }
111 111
112 return chi; 112 return chi;
113 } 113 }
114 114