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25 //
26 #include "globals.hh"
27 #include "G4ios.hh"
28 #include "G4PhysicalConstants.hh"
29 #include "G4XAnnihilationChannel.hh"
30 #include "G4KineticTrack.hh"
31 #include "G4ParticleDefinition.hh"
32 #include "G4ResonanceWidth.hh"
33 #include "G4ResonancePartialWidth.hh"
34 #include "G4PhysicsVector.hh"
35 #include "G4PartialWidthTable.hh"
36
37 G4XAnnihilationChannel::G4XAnnihilationChannel(): resonance(0)
38 {
39 // As a first approximation the model is assumed to be valid over
40 // the entire energy range
41 lowLimit = 0.;
42 highLimit = DBL_MAX;
43 widthTable = 0;
44 partWidthTable = 0;
45 }
46
47 G4XAnnihilationChannel::G4XAnnihilationChannel(const G4ParticleDefinition* resDefinition,
48 const G4ResonanceWidth& resWidths,
49 const G4ResonancePartialWidth& resPartWidths,
50 const G4String& partWidthLabel)
51 : resonance(resDefinition)
52 {
53 // Get the tabulated mass-dependent widths for the resonance
54 G4String resName = resonance->GetParticleName();
55 // cout << "HPW "<<resName<<endl;
56 G4String shortName = theNames.ShortName(resName);
57 // cout << "HPW "<<shortName<<endl;
58 // cout << "HPW "<<partWidthLabel<<endl;
59
60 widthTable = resWidths.MassDependentWidth(shortName);
61 partWidthTable = resPartWidths.MassDependentWidth(partWidthLabel);
62
63 // As a first approximation the model is assumed to be valid over
64 // the entire energy range
65 lowLimit = 0.;
66 highLimit = DBL_MAX;
67 }
68
69
70 G4XAnnihilationChannel::~G4XAnnihilationChannel()
71 {
72 if (widthTable) delete widthTable;
73 widthTable = 0;
74 if (partWidthTable) delete partWidthTable;
75 partWidthTable = 0;
76 }
77
78
79 G4bool G4XAnnihilationChannel::operator==(const G4XAnnihilationChannel &right) const
80 {
81 return (this == (G4XAnnihilationChannel *) &right);
82 }
83
84
85 G4bool G4XAnnihilationChannel::operator!=(const G4XAnnihilationChannel &right) const
86 {
87 return (this != (G4XAnnihilationChannel *) &right);
88 }
89
90
91 G4double G4XAnnihilationChannel::CrossSection(const G4KineticTrack& trk1,
92 const G4KineticTrack& trk2) const
93 {
94 G4double sigma = 0.;
95 G4double eCM = (trk1.Get4Momentum() + trk2.Get4Momentum()).mag();
96
97 const G4ParticleDefinition* def1 = trk1.GetDefinition();
98 const G4ParticleDefinition* def2 = trk2.GetDefinition();
99
100 G4int J1 = def1->GetPDGiSpin();
101 G4int J2 = def2->GetPDGiSpin();
102 G4double m_1 = def1->GetPDGMass();
103 G4double m_2 = def2->GetPDGMass();
104
105 G4int JRes = resonance->GetPDGiSpin();
106 G4double mRes = resonance->GetPDGMass();
107
108 G4double branch = Branch(trk1,trk2);
109 G4double width = VariableWidth(trk1,trk2);
110 G4double cleb = NormalizedClebsch(trk1,trk2);
111
112 G4double S = eCM * eCM;
113 if (S == 0.) throw G4HadronicException(__FILE__, __LINE__, "G4XAnnihilationChannel::CrossSection - eCM = 0");
114
115 G4double pCM = std::sqrt((S-(m_1+m_2)*(m_1+m_2))*(S-(m_1-m_2)*(m_1-m_2))/(4.*S));
116
117 sigma = ( (JRes + 1.) / ( (J1 + 1) * (J2 + 1) )
118 * pi / (pCM * pCM) * branch * width * width /
119 ( (eCM - mRes) * (eCM - mRes) + width * width / 4.0) * cleb * hbarc_squared);
120
121 // G4cout << "SS " << branch<<" "<<sigma<<" "
122 // << J1 <<" "
123 // <<J2<<" "
124 // <<m1<<" "
125 // <<m2<<" "
126 // <<JRes<<" "
127 // <<mRes<<" "
128 // <<wRes<<" "
129 // <<width<<" "
130 // <<cleb<<" "
131 // <<G4endl;
132 return sigma;
133 }
134
135
136 G4String G4XAnnihilationChannel::Name() const
137 {
138 G4String name("XAnnihilationChannelCrossSection");
139 return name;
140 }
141
142
143
144 G4bool G4XAnnihilationChannel::IsValid(G4double e) const
145 {
146 G4bool answer = InLimits(e,lowLimit,highLimit);
147
148 return answer;
149 }
150
151
152 G4double G4XAnnihilationChannel::Branch(const G4KineticTrack& trk1,
153 const G4KineticTrack& trk2) const
154 {
155 G4double w=VariableWidth(trk1,trk2);
156 if(w==0) return 0;
157 return VariablePartialWidth(trk1,trk2) / VariableWidth(trk1,trk2);
158 }
159
160 G4double G4XAnnihilationChannel::VariableWidth(const G4KineticTrack& trk1,
161 const G4KineticTrack& trk2) const
162 {
163 // actual production width of resonance, depending on available energy.
164
165 G4double width = resonance->GetPDGWidth();
166 G4bool dummy = false;
167 G4double sqrtS = (trk1.Get4Momentum() + trk2.Get4Momentum()).mag();
168 if (widthTable != 0)
169 {
170 width = widthTable->GetValue(sqrtS,dummy);
171 }
172 return width;
173 }
174
175
176 G4double G4XAnnihilationChannel::VariablePartialWidth(const G4KineticTrack& trk1,
177 const G4KineticTrack& trk2) const
178 {
179 // Calculate mass dependent partial width of resonance,
180 // based on UrQMD tabulations
181
182 G4double width(0);
183
184 if (partWidthTable != 0)
185 {
186 G4double sqrtS = 0;
187 G4bool dummy = false;
188 sqrtS = (trk1.Get4Momentum() + trk2.Get4Momentum()).mag();
189 width = partWidthTable->GetValue(sqrtS,dummy);
190 }
191 else
192 {
193 width = resonance->GetPDGWidth();
194 }
195 return width;
196 }
197
198
199 G4double G4XAnnihilationChannel::NormalizedClebsch(const G4KineticTrack& trk1,
200 const G4KineticTrack& trk2) const
201 {
202 G4double cleb = 0.;
203 const G4ParticleDefinition* def1 = trk1.GetDefinition();
204 const G4ParticleDefinition* def2 = trk2.GetDefinition();
205
206 G4int iso31 = def1->GetPDGiIsospin3();
207 G4int iso32 = def2->GetPDGiIsospin3();
208 G4int iso3 = iso31 + iso32;
209 G4int iso1 = def1->GetPDGiIsospin();
210 G4int iso2 = def2->GetPDGiIsospin();
211
212 G4int isoRes = resonance->GetPDGiIsospin();
213
214 if (isoRes < iso3) return 0.;
215 if ((iso1*iso2) == 0) return 1.;
216
217 cleb = clebsch.NormalizedClebschGordan(isoRes,iso3,iso1,iso2,iso31,iso32);
218
219 // Special case: particle-antiparticle, charge-conjugated states have the same weight
220 G4String type1 = def1->GetParticleType();
221 G4String type2 = def2->GetParticleType();
222 G4int anti = def1->GetPDGEncoding() * def2->GetPDGEncoding();
223 G4int strangeness = resonance->GetQuarkContent(3) + resonance->GetAntiQuarkContent(3);
224 if ( ((type1 == "baryon" && type2 == "baryon") ||(type1 == "meson" && type2 == "meson")) &&
225 anti < 0 && strangeness == 0)
226 {
227 if (def1->GetPDGEncoding() != -(def2->GetPDGEncoding())) cleb = 0.5 * cleb;
228 }
229
230 return cleb;
231 }
232
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237