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28 //
29 // 21.03.17 V. Grichine based on G4hBremsstrahlungModel
30 //
31 // Class Description:
32 //
33 // Implementation of energy loss for LDMPhoton emission by hadrons
34 //
35
36 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
37
38 #include "G4LDMBremModel.hh"
39
40 #include "TestParameters.hh"
41
42 #include "G4LDMPhoton.hh"
43 #include "G4Log.hh"
44 #include "G4ParticleChangeForLoss.hh"
45 #include "G4PhysicalConstants.hh"
46 #include "G4SystemOfUnits.hh"
47
48 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
49
50 using namespace std;
51
52 G4LDMBremModel::G4LDMBremModel(const G4ParticleDefinition* p, const G4String& nam)
53 : G4MuBremsstrahlungModel(p, nam)
54 {
55 fEpsilon = TestParameters::GetPointer()->GetAlphaFactor();
56 theLDMPhoton = G4LDMPhoton::LDMPhoton();
57 fLDMPhotonMass = theLDMPhoton->GetPDGMass();
58 minThreshold = 1.2 * fLDMPhotonMass;
59 }
60
61 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
62
63 G4LDMBremModel::~G4LDMBremModel() {}
64
65 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
66
67 G4double G4LDMBremModel::ComputeDEDXPerVolume(const G4Material*, const G4ParticleDefinition*,
68 G4double, G4double)
69 {
70 return 0.0;
71 }
72
73 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
74
75 G4double G4LDMBremModel::ComputeDMicroscopicCrossSection(G4double tkin, G4double Z,
76 G4double gammaEnergy)
77 // differential cross section
78 {
79 G4double dxsection = 0.;
80
81 if (gammaEnergy > tkin || tkin < minThreshold) return dxsection;
82 /*
83 G4cout << "G4LDMBremModel m= " << mass
84 << " " << particle->GetParticleName()
85 << " Egamma(GeV)= " << gammaEnergy/GeV
86 << " Ekin(GeV)= " << tkin/GeV << G4endl;
87 */
88 G4double E = tkin + mass;
89 G4double v = gammaEnergy / E;
90 G4double delta = 0.5 * mass * mass * v / (E - gammaEnergy);
91 G4double rab0 = delta * sqrte;
92
93 G4int iz = std::max(1, std::min(G4lrint(Z), 99));
94
95 G4double z13 = 1.0 / nist->GetZ13(iz);
96 G4double dn = mass * nist->GetA27(iz) / (70. * MeV);
97
98 G4double b = btf;
99 if (1 == iz) b = bh;
100
101 // nucleus contribution logarithm
102 G4double rab1 = b * z13;
103 G4double fn =
104 G4Log(rab1 / (dn * (electron_mass_c2 + rab0 * rab1)) * (mass + delta * (dn * sqrte - 2.)));
105 if (fn < 0.) fn = 0.;
106
107 G4double x = 1.0 - v;
108
109 if (particle->GetPDGSpin() != 0) {
110 x += 0.75 * v * v;
111 }
112
113 dxsection = coeff * x * Z * Z * fn / gammaEnergy;
114 return dxsection;
115 }
116
117 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
118
119 G4double G4LDMBremModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*,
120 G4double kineticEnergy, G4double Z, G4double,
121 G4double cutEnergy, G4double maxEnergy)
122 {
123 G4double cross = 0.0;
124
125 if (kineticEnergy <= lowestKinEnergy) return cross;
126
127 G4double tmax = std::min(maxEnergy, kineticEnergy);
128 G4double cut = std::min(cutEnergy, kineticEnergy);
129
130 cut = std::max(cut, minThreshold);
131 if (cut >= tmax) return cross;
132
133 cross = ComputeMicroscopicCrossSection(kineticEnergy, Z, cut);
134
135 if (tmax < kineticEnergy) {
136 cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
137 }
138 cross *= fEpsilon * fEpsilon;
139
140 return cross;
141 }
142
143 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
144
145 void G4LDMBremModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
146 const G4MaterialCutsCouple* couple,
147 const G4DynamicParticle* dp, G4double minEnergy,
148 G4double maxEnergy)
149 {
150 G4double kineticEnergy = dp->GetKineticEnergy();
151 // check against insufficient energy
152 G4double tmax = std::min(kineticEnergy, maxEnergy);
153 G4double tmin = std::min(kineticEnergy, minEnergy);
154 tmin = std::max(tmin, minThreshold);
155 if (tmin >= tmax) return;
156
157 // ===== sampling of energy transfer ======
158
159 G4ParticleMomentum partDirection = dp->GetMomentumDirection();
160
161 // select randomly one element constituing the material
162 const G4Element* anElement = SelectRandomAtom(couple, particle, kineticEnergy);
163 G4double Z = anElement->GetZ();
164
165 G4double totalEnergy = kineticEnergy + mass;
166 G4double totalMomentum = sqrt(kineticEnergy * (kineticEnergy + 2.0 * mass));
167
168 G4double func1 = tmin * ComputeDMicroscopicCrossSection(kineticEnergy, Z, tmin);
169
170 G4double lnepksi, epksi;
171 G4double func2;
172
173 G4double xmin = G4Log(tmin / MeV);
174 G4double xmax = G4Log(tmax / tmin);
175
176 do {
177 lnepksi = xmin + G4UniformRand() * xmax;
178 epksi = MeV * G4Exp(lnepksi);
179 func2 = epksi * ComputeDMicroscopicCrossSection(kineticEnergy, Z, epksi);
180
181 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
182 } while (func2 < func1 * G4UniformRand());
183
184 G4double gEnergy = std::max(epksi, fLDMPhotonMass);
185 G4double gMomentum = std::sqrt((epksi - fLDMPhotonMass) * (epksi + fLDMPhotonMass));
186
187 // ===== sample angle =====
188
189 G4double gam = totalEnergy / mass;
190 G4double rmax = gam * std::min(1.0, totalEnergy / gEnergy - 1.0);
191 G4double rmax2 = rmax * rmax;
192 G4double x = G4UniformRand() * rmax2 / (1.0 + rmax2);
193
194 G4double theta = std::sqrt(x / (1.0 - x)) / gam;
195 G4double sint = std::sin(theta);
196 G4double phi = twopi * G4UniformRand();
197 G4double dirx = sint * cos(phi), diry = sint * sin(phi), dirz = cos(theta);
198
199 G4ThreeVector gDirection(dirx, diry, dirz);
200 gDirection.rotateUz(partDirection);
201
202 partDirection *= totalMomentum;
203 partDirection -= gMomentum * gDirection;
204 partDirection = partDirection.unit();
205
206 // primary change
207
208 kineticEnergy -= gEnergy;
209
210 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
211 fParticleChange->SetProposedMomentumDirection(partDirection);
212
213 // save secondary
214 G4DynamicParticle* aLDMPhoton = new G4DynamicParticle(theLDMPhoton, gDirection, gEnergy);
215 vdp->push_back(aLDMPhoton);
216 }
217
218 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
219