| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4MollerBhabhaModel
33 //
34 // Author: Vladimir Ivanchenko on base of Laszlo Urban code
35 //
36 // Creation date: 03.01.2002
37 //
38 // Modifications:
39 //
40 // 13-11-02 Minor fix - use normalised direction (V.Ivanchenko)
41 // 04-12-02 Change G4DynamicParticle constructor in PostStepDoIt (V.Ivanchenko)
42 // 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
43 // 27-01-03 Make models region aware (V.Ivanchenko)
44 // 13-02-03 Add name (V.Ivanchenko)
45 // 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
46 // 25-07-05 Add protection in calculation of recoil direction for the case
47 // of complete energy transfer from e+ to e- (V.Ivanchenko)
48 // 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
49 // 15-05-06 Fix MinEnergyCut (V.Ivanchenko)
50 //
51 //
52 // Class Description:
53 //
54 // Implementation of energy loss and delta-electron production by e+/e-
55 //
56 // -------------------------------------------------------------------
57 //
58 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
59 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
60
61 #include "G4MollerBhabhaModel.hh"
62 #include "G4PhysicalConstants.hh"
63 #include "G4SystemOfUnits.hh"
64 #include "G4Electron.hh"
65 #include "G4Positron.hh"
66 #include "Randomize.hh"
67 #include "G4ParticleChangeForLoss.hh"
68 #include "G4Log.hh"
69 #include "G4DeltaAngle.hh"
70
71 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
72
73 using namespace std;
74
75 G4MollerBhabhaModel::G4MollerBhabhaModel(const G4ParticleDefinition* p,
76 const G4String& nam)
77 : G4VEmModel(nam),
78 particle(nullptr),
79 isElectron(true),
80 twoln10(2.0*G4Log(10.0)),
81 lowLimit(0.02*keV),
82 isInitialised(false)
83 {
84 theElectron = G4Electron::Electron();
85 if(nullptr != p) { SetParticle(p); }
86 fParticleChange = nullptr;
87 }
88
89 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
90
91 G4MollerBhabhaModel::~G4MollerBhabhaModel() = default;
92
93 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
94
95 G4double G4MollerBhabhaModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
96 G4double kinEnergy)
97 {
98 G4double tmax = kinEnergy;
99 if(isElectron) { tmax *= 0.5; }
100 return tmax;
101 }
102
103 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
104
105 void G4MollerBhabhaModel::Initialise(const G4ParticleDefinition* p,
106 const G4DataVector&)
107 {
108 if(p != particle) { SetParticle(p); }
109
110 if(isInitialised) { return; }
111
112 isInitialised = true;
113 fParticleChange = GetParticleChangeForLoss();
114 if(UseAngularGeneratorFlag() && !GetAngularDistribution()) {
115 SetAngularDistribution(new G4DeltaAngle());
116 }
117 }
118
119 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
120
121 G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron(
122 const G4ParticleDefinition* p, G4double kineticEnergy,
123 G4double cutEnergy, G4double maxEnergy)
124 {
125 if(p != particle) { SetParticle(p); }
126
127 G4double cross = 0.0;
128 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
129 tmax = std::min(maxEnergy, tmax);
130 //G4cout << "E= " << kineticEnergy << " cut= " << cutEnergy
131 // << " Emax= " << tmax << G4endl;
132 if(cutEnergy < tmax) {
133
134 G4double xmin = cutEnergy/kineticEnergy;
135 G4double xmax = tmax/kineticEnergy;
136 G4double tau = kineticEnergy/electron_mass_c2;
137 G4double gam = tau + 1.0;
138 G4double gamma2= gam*gam;
139 G4double beta2 = tau*(tau + 2)/gamma2;
140
141 //Moller (e-e-) scattering
142 if (isElectron) {
143
144 G4double gg = (2.0*gam - 1.0)/gamma2;
145 cross = ((xmax - xmin)*(1.0 - gg + 1.0/(xmin*xmax)
146 + 1.0/((1.0-xmin)*(1.0 - xmax)))
147 - gg*G4Log( xmax*(1.0 - xmin)/(xmin*(1.0 - xmax)) ) ) / beta2;
148
149 //Bhabha (e+e-) scattering
150 } else {
151
152 G4double y = 1.0/(1.0 + gam);
153 G4double y2 = y*y;
154 G4double y12 = 1.0 - 2.0*y;
155 G4double b1 = 2.0 - y2;
156 G4double b2 = y12*(3.0 + y2);
157 G4double y122= y12*y12;
158 G4double b4 = y122*y12;
159 G4double b3 = b4 + y122;
160
161 cross = (xmax - xmin)*(1.0/(beta2*xmin*xmax) + b2
162 - 0.5*b3*(xmin + xmax)
163 + b4*(xmin*xmin + xmin*xmax + xmax*xmax)/3.0)
164 - b1*G4Log(xmax/xmin);
165 }
166
167 cross *= twopi_mc2_rcl2/kineticEnergy;
168 }
169 return cross;
170 }
171
172 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
173
174 G4double G4MollerBhabhaModel::ComputeCrossSectionPerAtom(
175 const G4ParticleDefinition* p,
176 G4double kineticEnergy,
177 G4double Z, G4double,
178 G4double cutEnergy,
179 G4double maxEnergy)
180 {
181 return Z*ComputeCrossSectionPerElectron(p,kineticEnergy,cutEnergy,maxEnergy);
182 }
183
184 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
185
186 G4double G4MollerBhabhaModel::CrossSectionPerVolume(
187 const G4Material* material,
188 const G4ParticleDefinition* p,
189 G4double kinEnergy,
190 G4double cutEnergy,
191 G4double maxEnergy)
192 {
193 G4double eDensity = material->GetElectronDensity();
194 return eDensity*ComputeCrossSectionPerElectron(p,kinEnergy,cutEnergy,maxEnergy);
195 }
196
197 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
198
199 G4double G4MollerBhabhaModel::ComputeDEDXPerVolume(
200 const G4Material* material,
201 const G4ParticleDefinition* p,
202 G4double kineticEnergy,
203 G4double cut)
204 {
205 if(p != particle) { SetParticle(p); }
206 // calculate the dE/dx due to the ionization by Seltzer-Berger formula
207 // checl low-energy limit
208 G4double electronDensity = material->GetElectronDensity();
209
210 G4double Zeff = material->GetIonisation()->GetZeffective();
211 G4double th = 0.25*sqrt(Zeff)*keV;
212 G4double tkin = std::max(kineticEnergy, th);
213
214 G4double tau = tkin/electron_mass_c2;
215 G4double gam = tau + 1.0;
216 G4double gamma2= gam*gam;
217 G4double bg2 = tau*(tau + 2);
218 G4double beta2 = bg2/gamma2;
219
220 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
221 eexc /= electron_mass_c2;
222 G4double eexc2 = eexc*eexc;
223
224 G4double d = std::min(cut, MaxSecondaryEnergy(p, tkin))/electron_mass_c2;
225 G4double dedx;
226
227 // electron
228 if (isElectron) {
229
230 dedx = G4Log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2
231 + G4Log((tau-d)*d) + tau/(tau-d)
232 + (0.5*d*d + (2.0*tau + 1.)*G4Log(1. - d/tau))/gamma2;
233
234 //positron
235 } else {
236
237 G4double d2 = d*d*0.5;
238 G4double d3 = d2*d/1.5;
239 G4double d4 = d3*d*0.75;
240 G4double y = 1.0/(1.0 + gam);
241 dedx = G4Log(2.0*(tau + 2.0)/eexc2) + G4Log(tau*d)
242 - beta2*(tau + 2.0*d - y*(3.0*d2
243 + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau;
244 }
245
246 //density correction
247 G4double x = G4Log(bg2)/twoln10;
248 dedx -= material->GetIonisation()->DensityCorrection(x);
249
250 // now you can compute the total ionization loss
251 dedx *= twopi_mc2_rcl2*electronDensity/beta2;
252 if (dedx < 0.0) { dedx = 0.0; }
253
254 // lowenergy extrapolation
255
256 if (kineticEnergy < th) {
257 x = kineticEnergy/th;
258 if(x > 0.25) { dedx /= sqrt(x); }
259 else { dedx *= 1.4*sqrt(x)/(0.1 + x); }
260 }
261 return dedx;
262 }
263
264 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
265
266 void
267 G4MollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
268 const G4MaterialCutsCouple* couple,
269 const G4DynamicParticle* dp,
270 G4double cutEnergy,
271 G4double maxEnergy)
272 {
273 G4double kineticEnergy = dp->GetKineticEnergy();
274 //G4cout << "G4MollerBhabhaModel::SampleSecondaries: E= " << kineticEnergy
275 // << " in " << couple->GetMaterial()->GetName() << G4endl;
276 G4double tmax;
277 G4double tmin = cutEnergy;
278 if(isElectron) {
279 tmax = 0.5*kineticEnergy;
280 } else {
281 tmax = kineticEnergy;
282 }
283 if(maxEnergy < tmax) { tmax = maxEnergy; }
284 if(tmin >= tmax) { return; }
285
286 G4double energy = kineticEnergy + electron_mass_c2;
287 G4double xmin = tmin/kineticEnergy;
288 G4double xmax = tmax/kineticEnergy;
289 G4double gam = energy/electron_mass_c2;
290 G4double gamma2 = gam*gam;
291 G4double beta2 = 1.0 - 1.0/gamma2;
292 G4double x, z, grej;
293 CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
294 G4double rndm[2];
295
296 //Moller (e-e-) scattering
297 if (isElectron) {
298
299 G4double gg = (2.0*gam - 1.0)/gamma2;
300 G4double y = 1.0 - xmax;
301 grej = 1.0 - gg*xmax + xmax*xmax*(1.0 - gg + (1.0 - gg*y)/(y*y));
302
303 do {
304 rndmEngine->flatArray(2, rndm);
305 x = xmin*xmax/(xmin*(1.0 - rndm[0]) + xmax*rndm[0]);
306 y = 1.0 - x;
307 z = 1.0 - gg*x + x*x*(1.0 - gg + (1.0 - gg*y)/(y*y));
308 /*
309 if(z > grej) {
310 G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
311 << "Majorant " << grej << " < "
312 << z << " for x= " << x
313 << " e-e- scattering"
314 << G4endl;
315 }
316 */
317 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
318 } while(grej * rndm[1] > z);
319
320 //Bhabha (e+e-) scattering
321 } else {
322
323 G4double y = 1.0/(1.0 + gam);
324 G4double y2 = y*y;
325 G4double y12 = 1.0 - 2.0*y;
326 G4double b1 = 2.0 - y2;
327 G4double b2 = y12*(3.0 + y2);
328 G4double y122= y12*y12;
329 G4double b4 = y122*y12;
330 G4double b3 = b4 + y122;
331
332 y = xmax*xmax;
333 grej = 1.0 + (y*y*b4 - xmin*xmin*xmin*b3 + y*b2 - xmin*b1)*beta2;
334 do {
335 rndmEngine->flatArray(2, rndm);
336 x = xmin*xmax/(xmin*(1.0 - rndm[0]) + xmax*rndm[0]);
337 y = x*x;
338 z = 1.0 + (y*y*b4 - x*y*b3 + y*b2 - x*b1)*beta2;
339 /*
340 if(z > grej) {
341 G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
342 << "Majorant " << grej << " < "
343 << z << " for x= " << x
344 << " e+e- scattering"
345 << G4endl;
346 }
347 */
348 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
349 } while(grej * rndm[1] > z);
350 }
351
352 G4double deltaKinEnergy = x * kineticEnergy;
353
354 G4ThreeVector deltaDirection;
355
356 if(UseAngularGeneratorFlag()) {
357 const G4Material* mat = couple->GetMaterial();
358 G4int Z = SelectRandomAtomNumber(mat);
359
360 deltaDirection =
361 GetAngularDistribution()->SampleDirection(dp, deltaKinEnergy, Z, mat);
362
363 } else {
364
365 G4double deltaMomentum =
366 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
367 G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
368 (deltaMomentum * dp->GetTotalMomentum());
369 if(cost > 1.0) { cost = 1.0; }
370 G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
371
372 G4double phi = twopi * rndmEngine->flat() ;
373
374 deltaDirection.set(sint*cos(phi),sint*sin(phi), cost) ;
375 deltaDirection.rotateUz(dp->GetMomentumDirection());
376 }
377
378 // create G4DynamicParticle object for delta ray
379 auto delta = new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy);
380 vdp->push_back(delta);
381
382 // primary change
383 kineticEnergy -= deltaKinEnergy;
384 G4ThreeVector finalP = dp->GetMomentum() - delta->GetMomentum();
385 finalP = finalP.unit();
386
387 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
388 fParticleChange->SetProposedMomentumDirection(finalP);
389 }
390
391 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
392