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25 //
26 // @hpw@ misses the sampling of two breit wigner in a corelated fashion,
27 // @hpw@ to be usefull for resonance resonance scattering.
28
29 #include <typeinfo>
30
31 #include "globals.hh"
32 #include "G4SystemOfUnits.hh"
33 #include "G4VScatteringCollision.hh"
34 #include "G4KineticTrack.hh"
35 #include "G4VCrossSectionSource.hh"
36 #include "G4Proton.hh"
37 #include "G4Neutron.hh"
38 #include "G4XNNElastic.hh"
39 #include "G4AngularDistribution.hh"
40 #include "G4ThreeVector.hh"
41 #include "G4LorentzVector.hh"
42 #include "G4LorentzRotation.hh"
43 #include "G4KineticTrackVector.hh"
44 #include "Randomize.hh"
45 #include "G4PionPlus.hh"
46
47 G4VScatteringCollision::G4VScatteringCollision()
48 {
49 theAngularDistribution = new G4AngularDistribution(true);
50 }
51
52
53 G4VScatteringCollision::~G4VScatteringCollision()
54 {
55 delete theAngularDistribution;
56 theAngularDistribution=0;
57 }
58
59
60 G4KineticTrackVector* G4VScatteringCollision::FinalState(const G4KineticTrack& trk1,
61 const G4KineticTrack& trk2) const
62 {
63 const G4VAngularDistribution* angDistribution = GetAngularDistribution();
64 G4LorentzVector p = trk1.Get4Momentum() + trk2.Get4Momentum();
65 G4double sqrtS = p.m();
66 G4double S = sqrtS * sqrtS;
67
68 std::vector<const G4ParticleDefinition*> OutputDefinitions = GetOutgoingParticles();
69 if (OutputDefinitions.size() != 2)
70 throw G4HadronicException(__FILE__, __LINE__, "G4VScatteringCollision: Too many output particles!");
71
72 if (OutputDefinitions[0]->IsShortLived() && OutputDefinitions[1]->IsShortLived())
73 {
74 if(std::getenv("G4KCDEBUG")) G4cerr << "two shortlived for Type = "<<typeid(*this).name()<<G4endl;
75 // throw G4HadronicException(__FILE__, __LINE__, "G4VScatteringCollision: can't handle two shortlived particles!"); // @hpw@
76 }
77
78 G4double outm1 = OutputDefinitions[0]->GetPDGMass();
79 G4double outm2 = OutputDefinitions[1]->GetPDGMass();
80
81 if (OutputDefinitions[0]->IsShortLived())
82 {
83 outm1 = SampleResonanceMass(outm1,
84 OutputDefinitions[0]->GetPDGWidth(),
85 G4Neutron::NeutronDefinition()->GetPDGMass()+G4PionPlus::PionPlus()->GetPDGMass(),
86 sqrtS-(G4Neutron::NeutronDefinition()->GetPDGMass()+G4PionPlus::PionPlus()->GetPDGMass()));
87
88 }
89 if (OutputDefinitions[1]->IsShortLived())
90 {
91 outm2 = SampleResonanceMass(outm2, OutputDefinitions[1]->GetPDGWidth(),
92 G4Neutron::NeutronDefinition()->GetPDGMass()+G4PionPlus::PionPlus()->GetPDGMass(),
93 sqrtS-outm1);
94 }
95
96 // Angles of outgoing particles
97 G4double cosTheta = angDistribution->CosTheta(S, trk1.GetActualMass(), trk2.GetActualMass());
98 G4double phi = angDistribution->Phi();
99
100 // Unit vector of three-momentum
101 G4LorentzRotation fromCMSFrame(p.boostVector());
102 G4LorentzRotation toCMSFrame(fromCMSFrame.inverse());
103 G4LorentzVector TempPtr = toCMSFrame*trk1.Get4Momentum();
104 G4LorentzRotation toZ;
105 toZ.rotateZ(-1*TempPtr.phi());
106 toZ.rotateY(-1*TempPtr.theta());
107 G4LorentzRotation toCMS(toZ.inverse());
108
109 G4ThreeVector pFinal1(std::sin(std::acos(cosTheta))*std::cos(phi), std::sin(std::acos(cosTheta))*std::sin(phi), cosTheta);
110
111 // Three momentum in cm system
112 G4double pCM = std::sqrt( (S-(outm1+outm2)*(outm1+outm2)) * (S-(outm1-outm2)*(outm1-outm2)) /(4.*S));
113 pFinal1 = pFinal1 * pCM;
114 G4ThreeVector pFinal2 = -pFinal1;
115
116 G4double eFinal1 = std::sqrt(pFinal1.mag2() + outm1*outm1);
117 G4double eFinal2 = std::sqrt(pFinal2.mag2() + outm2*outm2);
118
119 G4LorentzVector p4Final1(pFinal1, eFinal1);
120 G4LorentzVector p4Final2(pFinal2, eFinal2);
121 p4Final1 = toCMS*p4Final1;
122 p4Final2 = toCMS*p4Final2;
123
124
125 // Lorentz transformation
126 G4LorentzRotation toLabFrame(p.boostVector());
127 p4Final1 *= toLabFrame;
128 p4Final2 *= toLabFrame;
129
130 // Final tracks are copies of incoming ones, with modified 4-momenta
131
132 G4double chargeBalance = OutputDefinitions[0]->GetPDGCharge()+OutputDefinitions[1]->GetPDGCharge();
133 chargeBalance-= trk1.GetDefinition()->GetPDGCharge();
134 chargeBalance-= trk2.GetDefinition()->GetPDGCharge();
135 if(std::abs(chargeBalance) >.1)
136 {
137 G4cout << "Charges in "<<typeid(*this).name()<<G4endl;
138 G4cout << OutputDefinitions[0]->GetPDGCharge()<<" "<<OutputDefinitions[0]->GetParticleName()
139 << OutputDefinitions[1]->GetPDGCharge()<<" "<<OutputDefinitions[1]->GetParticleName()
140 << trk1.GetDefinition()->GetPDGCharge()<<" "<<trk1.GetDefinition()->GetParticleName()
141 << trk2.GetDefinition()->GetPDGCharge()<<" "<<trk2.GetDefinition()->GetParticleName()<<G4endl;
142 }
143 G4KineticTrack* final1 = new G4KineticTrack(OutputDefinitions[0], 0.0, trk1.GetPosition(), p4Final1);
144 G4KineticTrack* final2 = new G4KineticTrack(OutputDefinitions[1], 0.0, trk2.GetPosition(), p4Final2);
145
146 G4KineticTrackVector* finalTracks = new G4KineticTrackVector;
147
148 finalTracks->push_back(final1);
149 finalTracks->push_back(final2);
150
151 return finalTracks;
152 }
153
154
155
156 double G4VScatteringCollision::SampleResonanceMass(const double poleMass,
157 const double gamma,
158 const double aMinMass,
159 const double maxMass) const
160 {
161 // Chooses a mass randomly between minMass and maxMass
162 // according to a Breit-Wigner function with constant
163 // width gamma and pole poleMass
164
165 G4double minMass = aMinMass;
166 if (minMass > maxMass) G4cerr << "##################### SampleResonanceMass: particle out of mass range" << G4endl;
167 if(minMass > maxMass) minMass -= G4PionPlus::PionPlus()->GetPDGMass();
168 if(minMass > maxMass) minMass = 0;
169
170 if (gamma < 1E-10*GeV)
171 return std::max(minMass,std::min(maxMass, poleMass));
172 else {
173 double fmin = BrWigInt0(minMass, gamma, poleMass);
174 double fmax = BrWigInt0(maxMass, gamma, poleMass);
175 double f = fmin + (fmax-fmin)*G4UniformRand();
176 return BrWigInv(f, gamma, poleMass);
177 }
178 }
179
180 void G4VScatteringCollision::establish_G4MT_TLS_G4VScatteringCollision()
181 {
182 establish_G4MT_TLS_G4VCollision();
183 if ( theAngularDistribution ) delete theAngularDistribution;
184 theAngularDistribution = new G4AngularDistribution(true);
185 }
186