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27 // -------------------------------------------------------------------
28 // GEANT4 Class file
29 //
30 // For information related to this code contact:
31 //
32 // File name: G4VXResonance
33 //
34 // Author:
35 //
36 // Creation date: 15 April 1999
37 //
38 // Modifications:
39 //
40 // -------------------------------------------------------------------
41
42 #include "globals.hh"
43 #include "G4ios.hh"
44 #include "G4KineticTrack.hh"
45 #include "G4VXResonance.hh"
46 #include "Randomize.hh"
47 #include "G4Proton.hh"
48 #include "G4HadTmpUtil.hh"
49
50 G4VXResonance::G4VXResonance()
51 { }
52
53
54 G4VXResonance::~G4VXResonance()
55 { }
56
57
58 G4bool G4VXResonance::operator==(const G4VXResonance &right) const
59 {
60 return (this == (G4VXResonance *) &right);
61 }
62
63
64 G4bool G4VXResonance::operator!=(const G4VXResonance &right) const
65 {
66 return (this != (G4VXResonance *) &right);
67 }
68
69
70 G4double G4VXResonance::IsospinCorrection(const G4KineticTrack& trk1,
71 const G4KineticTrack& trk2,
72 G4int isoOut1, G4int isoOut2,
73 G4double /*iSpinOut1*/, G4double /*iSpinOut2*/) const
74 {
75 G4double result = 0.;
76
77 const G4ParticleDefinition* in1 = trk1.GetDefinition();
78 const G4ParticleDefinition* in2 = trk2.GetDefinition();
79
80 G4int isoIn1 = in1->GetPDGiIsospin();
81 G4int iso3In1 = in1->GetPDGiIsospin3();
82 G4int isoIn2 = in2->GetPDGiIsospin();
83 G4int iso3In2 = in2->GetPDGiIsospin3();
84
85 G4int isoProton = G4Proton::ProtonDefinition()->GetPDGiIsospin();
86 G4int iso3Proton = G4Proton::ProtonDefinition()->GetPDGiIsospin3();
87
88 G4double pWeight = clebsch.Weight(isoProton,iso3Proton, isoProton,iso3Proton, isoOut1,isoOut2);
89 if (pWeight == 0.) throw G4HadronicException(__FILE__, __LINE__, "G4VXResonance::IsospinCorrection, no resonances - pWeight is zero");
90
91 if (in1->IsShortLived() || in2->IsShortLived())
92 {
93 // Resonances in the initial state
94 G4int iSpinProton = G4Proton::ProtonDefinition()->GetPDGiSpin();
95 G4double degeneracyFactor = DegeneracyFactor(trk1,trk2,iSpinProton,iSpinProton);
96
97 G4double factor = degeneracyFactor * pWeight;
98 if (factor > DBL_MIN)
99 {
100 // Randomly select the Isospin3 of the initial state resonances
101 std::vector<G4double> iso = clebsch.GenerateIso3(isoIn1,iso3In1,
102 isoIn2,iso3In2,
103 isoProton,isoProton);
104 G4int isoA = G4lrint(iso[0]);
105 G4int isoB = G4lrint(iso[1]);
106 G4double rWeight = clebsch.Weight(isoProton,isoA,
107 isoProton,isoB,
108 isoOut1,isoOut2);
109 result = rWeight / pWeight;
110 }
111 }
112 else
113 {
114 G4double weight = clebsch.Weight(isoIn1,iso3In1, isoIn2,iso3In2, isoOut1,isoOut2);
115 result = weight / pWeight;
116 }
117
118 return result;
119 }
120
121
122 #include "G4DetailedBalancePhaseSpaceIntegral.hh"
123
124 G4double G4VXResonance::DetailedBalance(const G4KineticTrack& trk1,
125 const G4KineticTrack& trk2,
126 G4int isoOut1, G4int isoOut2,
127 G4double iSpinOut1, G4double iSpinOut2,
128 G4double mOut1, G4double mOut2) const
129 {
130 // To handle the cases when resonances are involved the modified
131 // detailed balance of P. Danielewicz and G.F. Bertsch, Nucl. Phys. A533(1991) 712
132 // is used; in other words, the width of the resonances are folded to get the
133 // mean square of the final state momentum.
134
135 const G4ParticleDefinition* in1 = trk1.GetDefinition();
136 const G4ParticleDefinition* in2 = trk2.GetDefinition();
137 if(in1->IsShortLived() && in2->IsShortLived())
138 {
139 throw G4HadronicException(__FILE__, __LINE__, "Detailed balance for resonance scattering still on the schedule.");
140 }
141
142 G4double result = 0.;
143
144 G4int isoIn1 = in1->GetPDGiIsospin();
145 G4int iso3In1 = in1->GetPDGiIsospin3();
146 G4int isoIn2 = in2->GetPDGiIsospin();
147 G4int iso3In2 = in2->GetPDGiIsospin3();
148 G4double weight = clebsch.Weight(isoIn1, iso3In1, isoIn2, iso3In2, isoOut1, isoOut2);
149
150 if (weight > 00001)
151 {
152 // adding spin counting here ...... does not look quite consistent, but is correct anyway.
153 // revisit in the next design iteration @@
154 G4double degeneracy = DegeneracyFactor(trk1,trk2,iSpinOut1,iSpinOut2);
155 G4double factor = degeneracy * weight;
156
157 // now the phase-space
158 G4double S = (trk1.Get4Momentum() + trk2.Get4Momentum()).mag2();
159 G4double m_1 = in1->GetPDGMass();
160 G4double m_2 = in2->GetPDGMass();
161
162 // on-shell
163 G4double pinitial2 = (S - (m_1+m_2) * (m_1+m_2)) * (S - (m_1-m_2) * (m_1-m_2)) / (4.0*S);
164 G4double pfinal2 = (S - (mOut1+mOut2) * (mOut1+mOut2)) * (S - ( mOut1-mOut2) * (mOut1-mOut2)) / (4.0*S);
165 G4double relativeMomsquared = pfinal2/pinitial2;
166
167 // resonance-nucleon scattering - inverse channel
168 if(in1->IsShortLived())
169 {
170 G4DetailedBalancePhaseSpaceIntegral theI(in1);
171 relativeMomsquared = 1./theI.GetPhaseSpaceIntegral(std::sqrt(S));
172 }
173 else if(in2->IsShortLived())
174 {
175 G4DetailedBalancePhaseSpaceIntegral theI(in2);
176 relativeMomsquared = 1./theI.GetPhaseSpaceIntegral(std::sqrt(S));
177 }
178
179 result = factor * relativeMomsquared;
180 }
181
182 return result;
183 }
184
185
186 G4double G4VXResonance::DegeneracyFactor(const G4KineticTrack& trk1,
187 const G4KineticTrack& trk2,
188 G4double iSpinOut1, G4double iSpinOut2) const
189 {
190 G4double value = 0.;
191
192 const G4ParticleDefinition* in1 = trk1.GetDefinition();
193 const G4ParticleDefinition* in2 = trk2.GetDefinition();
194
195 G4double sIn1 = in1->GetPDGiSpin() + 1.;
196 G4double sIn2 = in2->GetPDGiSpin() + 1.;
197
198 G4double denom = sIn1 * sIn2;
199 if (denom > 0.)
200 {
201 value = (iSpinOut1+1) * (iSpinOut2+1) / denom;
202 }
203 return value;
204 }
205
206
207