source: trunk/source/processes/electromagnetic/muons/src/G4MuPairProductionModel.cc@ 1050

Last change on this file since 1050 was 1007, checked in by garnier, 17 years ago

update to geant4.9.2
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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 *
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24// ********************************************************************
25//
26// $Id: G4MuPairProductionModel.cc,v 1.39 2008/07/22 16:11:34 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4MuPairProductionModel
35//
36// Author: Vladimir Ivanchenko on base of Laszlo Urban code
37//
38// Creation date: 24.06.2002
39//
40// Modifications:
41//
42// 04-12-02 Change G4DynamicParticle constructor in PostStep (V.Ivanchenko)
43// 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
44// 24-01-03 Fix for compounds (V.Ivanchenko)
45// 27-01-03 Make models region aware (V.Ivanchenko)
46// 13-02-03 Add model (V.Ivanchenko)
47// 06-06-03 Fix in cross section calculation for high energy (V.Ivanchenko)
48// 20-10-03 2*xi in ComputeDDMicroscopicCrossSection (R.Kokoulin)
49// 8 integration points in ComputeDMicroscopicCrossSection
50// 12-01-04 Take min cut of e- and e+ not its sum (V.Ivanchenko)
51// 10-02-04 Update parameterisation using R.Kokoulin model (V.Ivanchenko)
52// 28-04-04 For complex materials repeat calculation of max energy for each
53// material (V.Ivanchenko)
54// 01-11-04 Fix bug inside ComputeDMicroscopicCrossSection (R.Kokoulin)
55// 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
56// 03-08-05 Add SetParticle method (V.Ivantchenko)
57// 23-10-05 Add protection in sampling of e+e- pair energy needed for
58// low cuts (V.Ivantchenko)
59// 13-02-06 Add ComputeCrossSectionPerAtom (mma)
60// 24-04-07 Add protection in SelectRandomAtom method (V.Ivantchenko)
61// 12-05-06 Updated sampling (use cut) in SelectRandomAtom (A.Bogdanov)
62// 11-10-07 Add ignoreCut flag (V.Ivanchenko)
63
64//
65// Class Description:
66//
67//
68// -------------------------------------------------------------------
69//
70//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
71//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
72
73#include "G4MuPairProductionModel.hh"
74#include "G4Electron.hh"
75#include "G4Positron.hh"
76#include "G4MuonMinus.hh"
77#include "G4MuonPlus.hh"
78#include "Randomize.hh"
79#include "G4Material.hh"
80#include "G4Element.hh"
81#include "G4ElementVector.hh"
82#include "G4ProductionCutsTable.hh"
83#include "G4ParticleChangeForLoss.hh"
84#include "G4ParticleChangeForGamma.hh"
85
86//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
87
88// static members
89//
90G4double G4MuPairProductionModel::zdat[]={1., 4., 13., 29., 92.};
91G4double G4MuPairProductionModel::adat[]={1.01, 9.01, 26.98, 63.55, 238.03};
92G4double G4MuPairProductionModel::tdat[]={1.e3, 1.e4, 1.e5, 1.e6, 1.e7, 1.e8,
93 1.e9, 1.e10};
94G4double G4MuPairProductionModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083,
95 0.5917, 0.7628, 0.8983, 0.9801 };
96G4double G4MuPairProductionModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813,
97 0.1813, 0.1569, 0.1112, 0.0506 };
98
99//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
100
101using namespace std;
102
103G4MuPairProductionModel::G4MuPairProductionModel(const G4ParticleDefinition* p,
104 const G4String& nam)
105 : G4VEmModel(nam),
106 particle(0),
107 factorForCross(4.*fine_structure_const*fine_structure_const
108 *classic_electr_radius*classic_electr_radius/(3.*pi)),
109 sqrte(sqrt(exp(1.))),
110 currentZ(0),
111 fParticleChange(0),
112 minPairEnergy(4.*electron_mass_c2),
113 lowestKinEnergy(1.*GeV),
114 nzdat(5),
115 ntdat(8),
116 nbiny(1000),
117 nmaxElements(0),
118 ymin(-5.),
119 ymax(0.),
120 dy((ymax-ymin)/nbiny),
121 samplingTablesAreFilled(false)
122{
123 SetLowEnergyLimit(minPairEnergy);
124 nist = G4NistManager::Instance();
125
126 theElectron = G4Electron::Electron();
127 thePositron = G4Positron::Positron();
128
129 if(p) SetParticle(p);
130}
131
132//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
133
134G4MuPairProductionModel::~G4MuPairProductionModel()
135{}
136
137//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
138
139void G4MuPairProductionModel::Initialise(const G4ParticleDefinition* p,
140 const G4DataVector&)
141{
142 if (!samplingTablesAreFilled) {
143 if(p) SetParticle(p);
144 MakeSamplingTables();
145 }
146 if(!fParticleChange) {
147 if(pParticleChange)
148 fParticleChange =
149 reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
150 else
151 fParticleChange = new G4ParticleChangeForLoss();
152 }
153}
154
155//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
156
157G4double G4MuPairProductionModel::ComputeDEDXPerVolume(
158 const G4Material* material,
159 const G4ParticleDefinition*,
160 G4double kineticEnergy,
161 G4double cutEnergy)
162{
163 G4double dedx = 0.0;
164 if (cutEnergy <= minPairEnergy || kineticEnergy <= lowestKinEnergy)
165 return dedx;
166
167 const G4ElementVector* theElementVector = material->GetElementVector();
168 const G4double* theAtomicNumDensityVector =
169 material->GetAtomicNumDensityVector();
170
171 // loop for elements in the material
172 for (size_t i=0; i<material->GetNumberOfElements(); i++) {
173 G4double Z = (*theElementVector)[i]->GetZ();
174 SetCurrentElement(Z);
175 G4double tmax = MaxSecondaryEnergy(particle, kineticEnergy);
176 G4double loss = ComputMuPairLoss(Z, kineticEnergy, cutEnergy, tmax);
177 dedx += loss*theAtomicNumDensityVector[i];
178 }
179 if (dedx < 0.) dedx = 0.;
180 return dedx;
181}
182
183//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
184
185G4double G4MuPairProductionModel::ComputMuPairLoss(G4double Z,
186 G4double tkin,
187 G4double cutEnergy,
188 G4double tmax)
189{
190 SetCurrentElement(Z);
191 G4double loss = 0.0;
192
193 G4double cut = std::min(cutEnergy,tmax);
194 if(cut <= minPairEnergy) return loss;
195
196 // calculate the rectricted loss
197 // numerical integration in log(PairEnergy)
198 G4double ak1=6.9;
199 G4double ak2=1.0;
200 G4double aaa = log(minPairEnergy);
201 G4double bbb = log(cut);
202 G4int kkk = (G4int)((bbb-aaa)/ak1+ak2);
203 if (kkk > 8) kkk = 8;
204 G4double hhh = (bbb-aaa)/(G4double)kkk;
205 G4double x = aaa;
206
207 for (G4int l=0 ; l<kkk; l++)
208 {
209
210 for (G4int ll=0; ll<8; ll++)
211 {
212 G4double ep = exp(x+xgi[ll]*hhh);
213 loss += wgi[ll]*ep*ep*ComputeDMicroscopicCrossSection(tkin, Z, ep);
214 }
215 x += hhh;
216 }
217 loss *= hhh;
218 if (loss < 0.) loss = 0.;
219 return loss;
220}
221
222//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
223
224G4double G4MuPairProductionModel::ComputeMicroscopicCrossSection(
225 G4double tkin,
226 G4double Z,
227 G4double cut)
228{
229 G4double cross = 0.;
230 SetCurrentElement(Z);
231 G4double tmax = MaxSecondaryEnergy(particle, tkin);
232 if (tmax <= cut) return cross;
233
234 G4double ak1=6.9 ;
235 G4double ak2=1.0 ;
236 G4double aaa = log(cut);
237 G4double bbb = log(tmax);
238 G4int kkk = (G4int)((bbb-aaa)/ak1 + ak2);
239 if(kkk > 8) kkk = 8;
240 G4double hhh = (bbb-aaa)/float(kkk);
241 G4double x = aaa;
242
243 for(G4int l=0; l<kkk; l++)
244 {
245 for(G4int i=0; i<8; i++)
246 {
247 G4double ep = exp(x + xgi[i]*hhh);
248 cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
249 }
250 x += hhh;
251 }
252
253 cross *=hhh;
254 if(cross < 0.0) cross = 0.0;
255 return cross;
256}
257
258G4double G4MuPairProductionModel::ComputeDMicroscopicCrossSection(
259 G4double tkin,
260 G4double Z,
261 G4double pairEnergy)
262 // Calculates the differential (D) microscopic cross section
263 // using the cross section formula of R.P. Kokoulin (18/01/98)
264 // Code modified by R.P. Kokoulin, V.N. Ivanchenko (27/01/04)
265{
266 G4double bbbtf= 183. ;
267 G4double bbbh = 202.4 ;
268 G4double g1tf = 1.95e-5 ;
269 G4double g2tf = 5.3e-5 ;
270 G4double g1h = 4.4e-5 ;
271 G4double g2h = 4.8e-5 ;
272
273 G4double totalEnergy = tkin + particleMass;
274 G4double residEnergy = totalEnergy - pairEnergy;
275 G4double massratio = particleMass/electron_mass_c2 ;
276 G4double massratio2 = massratio*massratio ;
277 G4double cross = 0.;
278
279 SetCurrentElement(Z);
280
281 G4double c3 = 0.75*sqrte*particleMass;
282 if (residEnergy <= c3*z13) return cross;
283
284 G4double c7 = 4.*electron_mass_c2;
285 G4double c8 = 6.*particleMass*particleMass;
286 G4double alf = c7/pairEnergy;
287 G4double a3 = 1. - alf;
288 if (a3 <= 0.) return cross;
289
290 // zeta calculation
291 G4double bbb,g1,g2;
292 if( Z < 1.5 ) { bbb = bbbh ; g1 = g1h ; g2 = g2h ; }
293 else { bbb = bbbtf; g1 = g1tf; g2 = g2tf; }
294
295 G4double zeta = 0;
296 G4double zeta1 = 0.073*log(totalEnergy/(particleMass+g1*z23*totalEnergy))-0.26;
297 if ( zeta1 > 0.)
298 {
299 G4double zeta2 = 0.058*log(totalEnergy/(particleMass+g2*z13*totalEnergy))-0.14;
300 zeta = zeta1/zeta2 ;
301 }
302
303 G4double z2 = Z*(Z+zeta);
304 G4double screen0 = 2.*electron_mass_c2*sqrte*bbb/(z13*pairEnergy);
305 G4double a0 = totalEnergy*residEnergy;
306 G4double a1 = pairEnergy*pairEnergy/a0;
307 G4double bet = 0.5*a1;
308 G4double xi0 = 0.25*massratio2*a1;
309 G4double del = c8/a0;
310
311 G4double rta3 = sqrt(a3);
312 G4double tmnexp = alf/(1. + rta3) + del*rta3;
313 if(tmnexp >= 1.0) return cross;
314
315 G4double tmn = log(tmnexp);
316 G4double sum = 0.;
317
318 // Gaussian integration in ln(1-ro) ( with 8 points)
319 for (G4int i=0; i<8; i++)
320 {
321 G4double a4 = exp(tmn*xgi[i]); // a4 = (1.-asymmetry)
322 G4double a5 = a4*(2.-a4) ;
323 G4double a6 = 1.-a5 ;
324 G4double a7 = 1.+a6 ;
325 G4double a9 = 3.+a6 ;
326 G4double xi = xi0*a5 ;
327 G4double xii = 1./xi ;
328 G4double xi1 = 1.+xi ;
329 G4double screen = screen0*xi1/a5 ;
330 G4double yeu = 5.-a6+4.*bet*a7 ;
331 G4double yed = 2.*(1.+3.*bet)*log(3.+xii)-a6-a1*(2.-a6) ;
332 G4double ye1 = 1.+yeu/yed ;
333 G4double ale=log(bbb/z13*sqrt(xi1*ye1)/(1.+screen*ye1)) ;
334 G4double cre = 0.5*log(1.+2.25*z23*xi1*ye1/massratio2) ;
335 G4double be;
336
337 if (xi <= 1.e3) be = ((2.+a6)*(1.+bet)+xi*a9)*log(1.+xii)+(a5-bet)/xi1-a9;
338 else be = (3.-a6+a1*a7)/(2.*xi);
339
340 G4double fe = (ale-cre)*be;
341 if ( fe < 0.) fe = 0. ;
342
343 G4double ymu = 4.+a6 +3.*bet*a7 ;
344 G4double ymd = a7*(1.5+a1)*log(3.+xi)+1.-1.5*a6 ;
345 G4double ym1 = 1.+ymu/ymd ;
346 G4double alm_crm = log(bbb*massratio/(1.5*z23*(1.+screen*ym1)));
347 G4double a10,bm;
348 if ( xi >= 1.e-3)
349 {
350 a10 = (1.+a1)*a5 ;
351 bm = (a7*(1.+1.5*bet)-a10*xii)*log(xi1)+xi*(a5-bet)/xi1+a10;
352 } else {
353 bm = (5.-a6+bet*a9)*(xi/2.);
354 }
355
356 G4double fm = alm_crm*bm;
357 if ( fm < 0.) fm = 0. ;
358
359 sum += wgi[i]*a4*(fe+fm/massratio2);
360 }
361
362 cross = -tmn*sum*factorForCross*z2*residEnergy/(totalEnergy*pairEnergy);
363
364 return cross;
365}
366
367//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
368
369G4double G4MuPairProductionModel::ComputeCrossSectionPerAtom(
370 const G4ParticleDefinition*,
371 G4double kineticEnergy,
372 G4double Z, G4double,
373 G4double cutEnergy,
374 G4double maxEnergy)
375{
376 G4double cross = 0.0;
377 if (kineticEnergy <= lowestKinEnergy) return cross;
378
379 SetCurrentElement(Z);
380 G4double tmax = std::min(maxEnergy, kineticEnergy);
381 G4double cut = std::min(cutEnergy, kineticEnergy);
382 if(cut < minPairEnergy) cut = minPairEnergy;
383 if (cut >= tmax) return cross;
384
385 cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut);
386 if(tmax < kineticEnergy) {
387 cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
388 }
389 return cross;
390}
391
392//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
393
394void G4MuPairProductionModel::MakeSamplingTables()
395{
396 for (G4int iz=0; iz<nzdat; iz++)
397 {
398 G4double Z = zdat[iz];
399 SetCurrentElement(Z);
400
401 for (G4int it=0; it<ntdat; it++) {
402
403 G4double kineticEnergy = tdat[it];
404 G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
405 // G4cout << "Z= " << currentZ << " z13= " << z13
406 //<< " mE= " << maxPairEnergy << G4endl;
407 G4double CrossSection = 0.0 ;
408
409 if(maxPairEnergy > minPairEnergy) {
410
411 G4double y = ymin - 0.5*dy ;
412 G4double yy = ymin - dy ;
413 G4double x = exp(y);
414 G4double fac = exp(dy);
415 G4double dx = exp(yy)*(fac - 1.0);
416
417 G4double c = log(maxPairEnergy/minPairEnergy);
418
419 for (G4int i=0 ; i<nbiny; i++) {
420 y += dy ;
421 if(c > 0.0) {
422 x *= fac;
423 dx*= fac;
424 G4double ep = minPairEnergy*exp(c*x) ;
425 CrossSection +=
426 ep*dx*ComputeDMicroscopicCrossSection(kineticEnergy, Z, ep);
427 }
428 ya[i] = y;
429 proba[iz][it][i] = CrossSection;
430 }
431
432 } else {
433 for (G4int i=0 ; i<nbiny; i++) {
434 proba[iz][it][i] = CrossSection;
435 }
436 }
437
438 ya[nbiny]=ymax;
439 proba[iz][it][nbiny] = CrossSection;
440
441 }
442 }
443 samplingTablesAreFilled = true;
444}
445
446//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
447
448void G4MuPairProductionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
449 const G4MaterialCutsCouple* couple,
450 const G4DynamicParticle* aDynamicParticle,
451 G4double tmin,
452 G4double tmax)
453{
454 G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
455 G4double totalEnergy = kineticEnergy + particleMass ;
456 G4ParticleMomentum ParticleDirection =
457 aDynamicParticle->GetMomentumDirection();
458
459 G4int it;
460 for(it=1; it<ntdat; it++) {if(kineticEnergy <= tdat[it]) break;}
461 if(it == ntdat) it--;
462 G4double dt = log(kineticEnergy/tdat[it-1])/log(tdat[it]/tdat[it-1]);
463
464 // select randomly one element constituing the material
465 const G4Element* anElement = SelectRandomAtom(kineticEnergy, dt, it, couple, tmin);
466 SetCurrentElement(anElement->GetZ());
467
468 // define interval of enegry transfer
469 G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
470 G4double maxEnergy = std::min(tmax, maxPairEnergy);
471 G4double minEnergy = std::max(tmin, minPairEnergy);
472
473 if(minEnergy >= maxEnergy) return;
474 //G4cout << "emin= " << minEnergy << " emax= " << maxEnergy
475 // << " minPair= " << minPairEnergy << " maxpair= " << maxPairEnergy
476 // << " ymin= " << ymin << " dy= " << dy << G4endl;
477
478 // select bins
479 G4int iymin = 0;
480 G4int iymax = nbiny-1;
481 if( minEnergy > minPairEnergy)
482 {
483 G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
484 iymin = (G4int)((log(xc) - ymin)/dy);
485 if(iymin >= nbiny) iymin = nbiny-1;
486 else if(iymin < 0) iymin = 0;
487 xc = log(maxEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
488 iymax = (G4int)((log(xc) - ymin)/dy) + 1;
489 if(iymax >= nbiny) iymax = nbiny-1;
490 else if(iymax < 0) iymax = 0;
491 }
492
493 // sample e-e+ energy, pair energy first
494 G4int iz, iy;
495
496 for(iz=1; iz<nzdat; iz++) {if(currentZ <= zdat[iz]) break;}
497 if(iz == nzdat) iz--;
498
499 G4double dz = log(currentZ/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
500
501 G4double pmin = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymin,currentZ);
502 G4double pmax = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymax,currentZ);
503
504 G4double p = pmin+G4UniformRand()*(pmax - pmin);
505
506 // interpolate sampling vector;
507 G4double p1 = pmin;
508 G4double p2 = pmin;
509 for(iy=iymin+1; iy<=iymax; iy++) {
510 p1 = p2;
511 p2 = InterpolatedIntegralCrossSection(dt, dz, iz, it, iy, currentZ);
512 if(p <= p2) break;
513 }
514 // G4cout << "iy= " << iy << " iymin= " << iymin << " iymax= "
515 // << iymax << " Z= " << currentZ << G4endl;
516 G4double y = ya[iy-1] + dy*(p - p1)/(p2 - p1);
517
518 G4double PairEnergy = minPairEnergy*exp(exp(y)
519 *log(maxPairEnergy/minPairEnergy));
520
521 if(PairEnergy < minEnergy) PairEnergy = minEnergy;
522 if(PairEnergy > maxEnergy) PairEnergy = maxEnergy;
523
524 // sample r=(E+-E-)/PairEnergy ( uniformly .....)
525 G4double rmax =
526 (1.-6.*particleMass*particleMass/(totalEnergy*(totalEnergy-PairEnergy)))
527 *sqrt(1.-minPairEnergy/PairEnergy);
528 G4double r = rmax * (-1.+2.*G4UniformRand()) ;
529
530 // compute energies from PairEnergy,r
531 G4double ElectronEnergy = (1.-r)*PairEnergy*0.5;
532 G4double PositronEnergy = PairEnergy - ElectronEnergy;
533
534 // angles of the emitted particles ( Z - axis along the parent particle)
535 // (mean theta for the moment)
536
537 //
538 // scattered electron (positron) angles. ( Z - axis along the parent photon)
539 //
540 // universal distribution suggested by L. Urban
541 // (Geant3 manual (1993) Phys211),
542 // derived from Tsai distribution (Rev Mod Phys 49,421(1977))
543 // G4cout << "Ee= " << ElectronEnergy << " Ep= " << PositronEnergy << G4endl;
544 G4double u;
545 const G4double a1 = 0.625 , a2 = 3.*a1 , d = 27. ;
546
547 if (9./(9.+d) >G4UniformRand()) u= - log(G4UniformRand()*G4UniformRand())/a1;
548 else u= - log(G4UniformRand()*G4UniformRand())/a2;
549
550 G4double TetEl = u*electron_mass_c2/ElectronEnergy;
551 G4double TetPo = u*electron_mass_c2/PositronEnergy;
552 G4double Phi = twopi * G4UniformRand();
553 G4double dxEl= sin(TetEl)*cos(Phi),dyEl= sin(TetEl)*sin(Phi),dzEl=cos(TetEl);
554 G4double dxPo=-sin(TetPo)*cos(Phi),dyPo=-sin(TetPo)*sin(Phi),dzPo=cos(TetPo);
555
556 G4ThreeVector ElectDirection (dxEl, dyEl, dzEl);
557 ElectDirection.rotateUz(ParticleDirection);
558
559 // create G4DynamicParticle object for the particle1
560 G4DynamicParticle* aParticle1= new G4DynamicParticle(theElectron,
561 ElectDirection,
562 ElectronEnergy - electron_mass_c2);
563
564 G4ThreeVector PositDirection (dxPo, dyPo, dzPo);
565 PositDirection.rotateUz(ParticleDirection);
566
567 // create G4DynamicParticle object for the particle2
568 G4DynamicParticle* aParticle2 =
569 new G4DynamicParticle(thePositron,
570 PositDirection,
571 PositronEnergy - electron_mass_c2);
572
573 // primary change
574 kineticEnergy -= (ElectronEnergy + PositronEnergy);
575 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
576
577 vdp->push_back(aParticle1);
578 vdp->push_back(aParticle2);
579}
580
581//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
582
583const G4Element* G4MuPairProductionModel::SelectRandomAtom(
584 G4double kinEnergy, G4double dt, G4int it,
585 const G4MaterialCutsCouple* couple, G4double tmin)
586{
587 // select randomly 1 element within the material
588
589 const G4Material* material = couple->GetMaterial();
590 size_t nElements = material->GetNumberOfElements();
591 const G4ElementVector* theElementVector = material->GetElementVector();
592 if (nElements == 1) return (*theElementVector)[0];
593
594 if(nElements > nmaxElements) {
595 nmaxElements = nElements;
596 partialSum.resize(nmaxElements);
597 }
598
599 const G4double* theAtomNumDensityVector=material->GetAtomicNumDensityVector();
600
601 G4double sum = 0.0;
602
603 size_t i;
604 for (i=0; i<nElements; i++) {
605 G4double Z = ((*theElementVector)[i])->GetZ();
606 SetCurrentElement(Z);
607 G4double maxPairEnergy = MaxSecondaryEnergy(particle,kinEnergy);
608 G4double minEnergy = std::max(tmin, minPairEnergy);
609
610 G4int iz;
611 for(iz=1; iz<nzdat; iz++) {if(Z <= zdat[iz]) break;}
612 if(iz == nzdat) iz--;
613 G4double dz = log(Z/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
614
615 G4double sigcut;
616 if(minEnergy <= minPairEnergy)
617 sigcut = 0.;
618 else
619 {
620 G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
621 G4int iy = (G4int)((log(xc) - ymin)/dy);
622 if(iy < 0) iy = 0;
623 if(iy >= nbiny) iy = nbiny-1;
624 sigcut = InterpolatedIntegralCrossSection(dt,dz,iz,it,iy, Z);
625 }
626
627 G4double sigtot = InterpolatedIntegralCrossSection(dt,dz,iz,it,nbiny,Z);
628 G4double dl = (sigtot - sigcut)*theAtomNumDensityVector[i];
629
630 // protection
631 if(dl < 0.0) dl = 0.0;
632 sum += dl;
633 partialSum[i] = sum;
634 }
635
636 G4double rval = G4UniformRand()*sum;
637 for (i=0; i<nElements; i++) {
638 if(rval<=partialSum[i]) return (*theElementVector)[i];
639 }
640
641 return (*theElementVector)[nElements - 1];
642
643}
644
645//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
646
647
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