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25 //
26 // INCL++ intra-nuclear cascade model
27 // Alain Boudard, CEA-Saclay, France
28 // Joseph Cugnon, University of Liege, Belgium
29 // Jean-Christophe David, CEA-Saclay, France
30 // Pekka Kaitaniemi, CEA-Saclay, France, and Helsinki Institute of Physics, Finland
31 // Sylvie Leray, CEA-Saclay, France
32 // Davide Mancusi, CEA-Saclay, France
33 //
34 #define INCLXX_IN_GEANT4_MODE 1
35
36 #include "globals.hh"
37
38 #include "G4INCLPhaseSpaceGenerator.hh"
39 #include "G4INCLPhaseSpaceKopylov.hh"
40 #include "G4INCLPhaseSpaceRauboldLynch.hh"
41
42 namespace G4INCL {
43
44 namespace {
45 G4ThreadLocal IPhaseSpaceGenerator *thePhaseSpaceGenerator;
46
47 G4ThreadLocal Particle *biasMe;
48
49 /** \brief Actually perform the biasing
50 *
51 * \param particles list of particles to bias
52 * \param pInVec momentum of the particle to be biased before the collision
53 * \param slope the parameter \f$B\f$ in \f$\exp(B\cdot t)\f$
54 */
55 void bias(ParticleList &particles, const ThreeVector &pInVec, const G4double slope) {
56 const G4double pIn = pInVec.mag();
57 const ThreeVector collisionAxis = pInVec/pIn;
58 const ThreeVector pMomVec = biasMe->getMomentum();
59 const G4double pMom = pMomVec.mag();
60 if(pMom ==0.) return;
61 const G4double pMomCosAng = pMomVec.dot(collisionAxis)/pMom;
62 const G4double pMomAng = Math::arcCos(pMomCosAng); // Angle between the original axis of the dominant particle and is new one after generate
63
64 // compute the target angle for the biasing
65 // it is drawn from a exp(Bt) distribution
66 const G4double cosAngSlope = 2e-6 * slope * pIn * pMom;
67 const G4double cosAng = 1. + std::log(1. - Random::shoot()*(1.-std::exp(-2.*cosAngSlope)))/cosAngSlope;
68 const G4double ang = Math::arcCos(cosAng);
69
70 // compute the rotation angle
71 const G4double rotationAngle = ang - pMomAng;
72
73 // generate the rotation axis; it is perpendicular to collisionAxis and
74 // pMomVec
75 ThreeVector rotationAxis;
76 if(pMomAng>1E-10) {
77 rotationAxis = collisionAxis.vector(pMomVec);
78 const G4double axisLength = rotationAxis.mag();
79 const G4double oneOverLength = 1./axisLength;
80 rotationAxis *= oneOverLength;
81 } else {
82 // need to jump through some hoops if collisionAxis is nearly aligned
83 // with pMomVec
84 rotationAxis = collisionAxis.anyOrthogonal();
85 }
86
87 // apply the rotation
88 particles.rotateMomentum(rotationAngle, rotationAxis);
89 }
90
91 }
92
93 namespace PhaseSpaceGenerator {
94 void generate(const G4double sqrtS, ParticleList &particles) {
95 return thePhaseSpaceGenerator->generate(sqrtS, particles);
96 }
97
98 void generateBiased(const G4double sqrtS, ParticleList &particles, const size_t index, const G4double slope) {
99 // assert(index<particles.size());
100 // store the incoming momentum of particle[index]; it will be used to
101 // compute t when biasing
102 biasMe = particles[index];
103 const ThreeVector pInVec = biasMe->getMomentum();
104 generate(sqrtS, particles);
105 // Extremely rare event try to bias with vector null
106 if(pInVec.mag() != 0.) bias(particles, pInVec, slope);
107 }
108
109 void setPhaseSpaceGenerator(IPhaseSpaceGenerator *g) {
110 thePhaseSpaceGenerator = g;
111 }
112
113 IPhaseSpaceGenerator *getPhaseSpaceGenerator() {
114 return thePhaseSpaceGenerator;
115 }
116
117 void deletePhaseSpaceGenerator() {
118 delete thePhaseSpaceGenerator;
119 thePhaseSpaceGenerator = NULL;
120 }
121
122 void initialize(Config const * const theConfig) {
123 PhaseSpaceGeneratorType psg = theConfig->getPhaseSpaceGeneratorType();
124 if(psg==RauboldLynchType)
125 setPhaseSpaceGenerator(new PhaseSpaceRauboldLynch);
126 else if(psg==KopylovType)
127 setPhaseSpaceGenerator(new PhaseSpaceKopylov);
128 else
129 setPhaseSpaceGenerator(NULL);
130 }
131 }
132 }
133