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27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4MuBremsstrahlungModel
33 //
34 // Author: Vladimir Ivanchenko on base of Laszlo Urban code
35 //
36 // Creation date: 24.06.2002
37 //
38 // Modifications:
39 //
40 // 04-12-02 Change G4DynamicParticle constructor in PostStepDoIt (V.Ivanchenko)
41 // 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
42 // 24-01-03 Fix for compounds (V.Ivanchenko)
43 // 27-01-03 Make models region aware (V.Ivanchenko)
44 // 13-02-03 Add name (V.Ivanchenko)
45 // 10-02-04 Add lowestKinEnergy (V.Ivanchenko)
46 // 08-04-05 Major optimisation of internal interfaces (V.Ivanchenko)
47 // 03-08-05 Angular correlations according to PRM (V.Ivanchenko)
48 // 13-02-06 add ComputeCrossSectionPerAtom (mma)
49 // 21-03-06 Fix problem of initialisation in case when cuts are not defined (VI)
50 // 07-11-07 Improve sampling of final state (A.Bogdanov)
51 // 28-02-08 Use precomputed Z^1/3 and Log(A) (V.Ivanchenko)
52 // 31-05-13 Use element selectors instead of local data structure (V.Ivanchenko)
53 //
54 // -------------------------------------------------------------------
55 //
56 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
57 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
58
59 #include "G4MuBremsstrahlungModel.hh"
60 #include "G4PhysicalConstants.hh"
61 #include "G4SystemOfUnits.hh"
62 #include "G4Gamma.hh"
63 #include "G4MuonMinus.hh"
64 #include "G4MuonPlus.hh"
65 #include "Randomize.hh"
66 #include "G4Material.hh"
67 #include "G4Element.hh"
68 #include "G4ElementVector.hh"
69 #include "G4ProductionCutsTable.hh"
70 #include "G4ModifiedMephi.hh"
71 #include "G4ParticleChangeForLoss.hh"
72 #include "G4Log.hh"
73
74 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
75 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
76
77 const G4double G4MuBremsstrahlungModel::xgi[] =
78 {0.03377,0.16940,0.38069,0.61931,0.83060,0.96623};
79 const G4double G4MuBremsstrahlungModel::wgi[] =
80 {0.08566,0.18038,0.23396,0.23396,0.18038,0.08566};
81 G4double G4MuBremsstrahlungModel::fDN[] = {0.0};
82
83 G4MuBremsstrahlungModel::G4MuBremsstrahlungModel(const G4ParticleDefinition* p,
84 const G4String& nam)
85 : G4VEmModel(nam),
86 sqrte(std::sqrt(G4Exp(1.))),
87 lowestKinEnergy(0.1*CLHEP::GeV),
88 minThreshold(0.9*CLHEP::keV)
89 {
90 theGamma = G4Gamma::Gamma();
91 nist = G4NistManager::Instance();
92
93 SetAngularDistribution(new G4ModifiedMephi());
94
95 if (nullptr != p) { SetParticle(p); }
96 if (0.0 == fDN[1]) {
97 for (G4int i=1; i<93; ++i) {
98 G4double dn = 1.54*nist->GetA27(i);
99 fDN[i] = dn;
100 if(1 < i) {
101 fDN[i] /= std::pow(dn, 1./G4double(i));
102 }
103 }
104 }
105 }
106
107 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
108
109 G4double G4MuBremsstrahlungModel::MinEnergyCut(const G4ParticleDefinition*,
110 const G4MaterialCutsCouple*)
111 {
112 return minThreshold;
113 }
114
115 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
116
117 G4double G4MuBremsstrahlungModel::MinPrimaryEnergy(const G4Material*,
118 const G4ParticleDefinition*,
119 G4double cut)
120 {
121 return std::max(lowestKinEnergy, cut);
122 }
123
124 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
125
126 void G4MuBremsstrahlungModel::SetParticle(const G4ParticleDefinition* p)
127 {
128 if(nullptr == particle) {
129 particle = p;
130 mass = particle->GetPDGMass();
131 rmass = mass/CLHEP::electron_mass_c2 ;
132 cc = CLHEP::classic_electr_radius/rmass ;
133 coeff = 16.*CLHEP::fine_structure_const*cc*cc/3. ;
134 }
135 }
136
137 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
138
139 void G4MuBremsstrahlungModel::Initialise(const G4ParticleDefinition* p,
140 const G4DataVector& cuts)
141 {
142 SetParticle(p);
143 if(nullptr == fParticleChange) {
144 fParticleChange = GetParticleChangeForLoss();
145 }
146 if(IsMaster() && p == particle && lowestKinEnergy < HighEnergyLimit()) {
147 InitialiseElementSelectors(p, cuts);
148 }
149 }
150
151 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
152
153 void G4MuBremsstrahlungModel::InitialiseLocal(const G4ParticleDefinition* p,
154 G4VEmModel* masterModel)
155 {
156 if(p == particle && lowestKinEnergy < HighEnergyLimit()) {
157 SetElementSelectors(masterModel->GetElementSelectors());
158 }
159 }
160
161 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
162
163 G4double G4MuBremsstrahlungModel::ComputeDEDXPerVolume(
164 const G4Material* material,
165 const G4ParticleDefinition*,
166 G4double kineticEnergy,
167 G4double cutEnergy)
168 {
169 G4double dedx = 0.0;
170 if (kineticEnergy <= lowestKinEnergy) { return dedx; }
171
172 G4double cut = std::max(cutEnergy, minThreshold);
173 cut = std::min(cut, kineticEnergy);
174
175 const G4ElementVector* theElementVector = material->GetElementVector();
176 const G4double* theAtomicNumDensityVector =
177 material->GetAtomicNumDensityVector();
178
179 // loop for elements in the material
180 for (size_t i=0; i<material->GetNumberOfElements(); ++i) {
181 G4double loss =
182 ComputMuBremLoss((*theElementVector)[i]->GetZ(), kineticEnergy, cut);
183 dedx += loss*theAtomicNumDensityVector[i];
184 }
185 // G4cout << "BR e= " << kineticEnergy << " dedx= " << dedx << G4endl;
186 dedx = std::max(dedx, 0.);
187 return dedx;
188 }
189
190 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
191
192 G4double G4MuBremsstrahlungModel::ComputMuBremLoss(G4double Z,
193 G4double tkin, G4double cut)
194 {
195 G4double totalEnergy = mass + tkin;
196 static const G4double ak1 = 0.05;
197 static const G4int k2 = 5;
198 G4double loss = 0.;
199
200 G4double vcut = cut/totalEnergy;
201 G4int kkk = (G4int)(vcut/ak1) + k2;
202 if (kkk > 8) { kkk = 8; }
203 else if (kkk < 1) { kkk = 1; }
204 G4double hhh = vcut/(G4double)(kkk);
205
206 G4double aa = 0.;
207 for(G4int l=0; l<kkk; ++l) {
208 for(G4int i=0; i<6; ++i) {
209 G4double ep = (aa + xgi[i]*hhh)*totalEnergy;
210 loss += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
211 }
212 aa += hhh;
213 }
214
215 loss *= hhh*totalEnergy;
216 return loss;
217 }
218
219 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
220
221 G4double G4MuBremsstrahlungModel::ComputeMicroscopicCrossSection(
222 G4double tkin,
223 G4double Z,
224 G4double cut)
225 {
226 G4double totalEnergy = tkin + mass;
227 static const G4double ak1 = 2.3;
228 static const G4int k2 = 4;
229 G4double cross = 0.;
230
231 if(cut >= tkin) return cross;
232
233 G4double vcut = cut/totalEnergy;
234 G4double vmax = tkin/totalEnergy;
235
236 G4double aaa = G4Log(vcut);
237 G4double bbb = G4Log(vmax);
238 G4int kkk = (G4int)((bbb-aaa)/ak1) + k2 ;
239 if(kkk > 8) { kkk = 8; }
240 else if (kkk < 1) { kkk = 1; }
241 G4double hhh = (bbb-aaa)/(G4double)(kkk);
242 G4double aa = aaa;
243
244 for(G4int l=0; l<kkk; ++l) {
245 for(G4int i=0; i<6; ++i) {
246 G4double ep = G4Exp(aa + xgi[i]*hhh)*totalEnergy;
247 cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
248 }
249 aa += hhh;
250 }
251
252 cross *= hhh;
253 //G4cout << "BR e= " << tkin<< " cross= " << cross/barn << G4endl;
254 return cross;
255 }
256
257 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
258
259 G4double G4MuBremsstrahlungModel::ComputeDMicroscopicCrossSection(
260 G4double tkin,
261 G4double Z,
262 G4double gammaEnergy)
263 // differential cross section
264 {
265 G4double dxsection = 0.;
266 if(gammaEnergy > tkin) { return dxsection; }
267
268 G4double E = tkin + mass ;
269 G4double v = gammaEnergy/E ;
270 G4double delta = 0.5*mass*mass*v/(E-gammaEnergy) ;
271 G4double rab0 = delta*sqrte ;
272
273 G4int iz = G4lrint(Z);
274 if(iz < 1) { iz = 1; }
275 else if(iz > 92) { iz = 92; }
276
277 G4double z13 = 1.0/nist->GetZ13(iz);
278 G4double dnstar = fDN[iz];
279
280 G4double b,b1;
281 if(1 == iz) {
282 b = bh;
283 b1 = bh1;
284 } else {
285 b = btf;
286 b1 = btf1;
287 }
288
289 // nucleus contribution logarithm
290 G4double rab1 = b*z13;
291 G4double fn = G4Log(rab1/(dnstar*(CLHEP::electron_mass_c2+rab0*rab1))*
292 (mass + delta*(dnstar*sqrte-2.)));
293 fn = std::max(fn, 0.);
294 // electron contribution logarithm
295 G4double epmax1 = E/(1.+0.5*mass*rmass/E);
296 G4double fe = 0.;
297 if(gammaEnergy < epmax1) {
298 G4double rab2 = b1*z13*z13;
299 fe = G4Log(rab2*mass/((1.+delta*rmass/(CLHEP::electron_mass_c2*sqrte))*
300 (CLHEP::electron_mass_c2+rab0*rab2)));
301 fe = std::max(fe, 0.);
302 }
303
304 dxsection = coeff*(1.-v*(1. - 0.75*v))*Z*(fn*Z + fe)/gammaEnergy;
305 dxsection = std::max(dxsection, 0.0);
306 return dxsection;
307 }
308
309 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
310
311 G4double G4MuBremsstrahlungModel::ComputeCrossSectionPerAtom(
312 const G4ParticleDefinition*,
313 G4double kineticEnergy,
314 G4double Z, G4double,
315 G4double cutEnergy,
316 G4double maxEnergy)
317 {
318 G4double cross = 0.0;
319 if (kineticEnergy <= lowestKinEnergy) return cross;
320 G4double tmax = std::min(maxEnergy, kineticEnergy);
321 G4double cut = std::min(cutEnergy, kineticEnergy);
322 if (cut < minThreshold) cut = minThreshold;
323 if (cut >= tmax) return cross;
324
325 cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut);
326 if(tmax < kineticEnergy) {
327 cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
328 }
329 return cross;
330 }
331
332 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
333
334 void G4MuBremsstrahlungModel::SampleSecondaries(
335 std::vector<G4DynamicParticle*>* vdp,
336 const G4MaterialCutsCouple* couple,
337 const G4DynamicParticle* dp,
338 G4double minEnergy,
339 G4double maxEnergy)
340 {
341 G4double kineticEnergy = dp->GetKineticEnergy();
342 // check against insufficient energy
343 G4double tmax = std::min(kineticEnergy, maxEnergy);
344 G4double tmin = std::min(kineticEnergy, minEnergy);
345 tmin = std::max(tmin, minThreshold);
346 if(tmin >= tmax) return;
347
348 // ===== sampling of energy transfer ======
349
350 G4ParticleMomentum partDirection = dp->GetMomentumDirection();
351
352 // select randomly one element constituing the material
353 const G4Element* anElement = SelectRandomAtom(couple,particle,kineticEnergy);
354 G4double Z = anElement->GetZ();
355 G4double func1 = tmin*
356 ComputeDMicroscopicCrossSection(kineticEnergy, Z, tmin);
357
358 G4double gEnergy;
359 G4double func2;
360
361 G4double xmin = G4Log(tmin/minThreshold);
362 G4double xmax = G4Log(tmax/tmin);
363
364 do {
365 gEnergy = minThreshold*G4Exp(xmin + G4UniformRand()*xmax);
366 func2 = gEnergy*ComputeDMicroscopicCrossSection(kineticEnergy, Z, gEnergy);
367
368 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
369 } while(func2 < func1*G4UniformRand());
370
371 // angles of the emitted gamma using general interface
372 G4ThreeVector gamDir =
373 GetAngularDistribution()->SampleDirection(dp, gEnergy, Z,
374 couple->GetMaterial());
375 // create G4DynamicParticle object for the Gamma
376 G4DynamicParticle* gamma = new G4DynamicParticle(theGamma, gamDir, gEnergy);
377 vdp->push_back(gamma);
378
379 // compute post-interaction kinematics of primary e-/e+ based on
380 // energy-momentum conservation
381 const G4double totMomentum =
382 std::sqrt(kineticEnergy*(kineticEnergy + 2.0*mass));
383 G4ThreeVector dir =
384 (totMomentum*dp->GetMomentumDirection() - gEnergy*gamDir).unit();
385 const G4double finalE = kineticEnergy - gEnergy;
386
387 // if secondary gamma energy is higher than threshold(very high by default)
388 // then stop tracking the primary particle and create new secondary e-/e+
389 // instead of the primary one
390 if (gEnergy > SecondaryThreshold()) {
391 fParticleChange->ProposeTrackStatus(fStopAndKill);
392 fParticleChange->SetProposedKineticEnergy(0.0);
393 G4DynamicParticle* newdp = new G4DynamicParticle(particle, dir, finalE);
394 vdp->push_back(newdp);
395 } else {
396 // continue tracking the primary e-/e+ otherwise
397 fParticleChange->SetProposedMomentumDirection(dir);
398 fParticleChange->SetProposedKineticEnergy(finalE);
399 }
400 }
401
402 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
403