source: trunk/source/processes/electromagnetic/muons/src/G4MuPairProductionModel.cc @ 1316

Last change on this file since 1316 was 1315, checked in by garnier, 14 years ago

update geant4-09-04-beta-cand-01 interfaces-V09-03-09 vis-V09-03-08
File size: 21.7 KB
Line 
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// $Id: G4MuPairProductionModel.cc,v 1.45 2010/06/01 15:21:59 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-04-beta-cand-01 $
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
139G4double G4MuPairProductionModel::MinEnergyCut(const G4ParticleDefinition*,
140                                               const G4MaterialCutsCouple* )
141{
142  return minPairEnergy;
143}
144
145//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
146
147G4double G4MuPairProductionModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
148                                                     G4double kineticEnergy)
149{
150  G4double maxPairEnergy = kineticEnergy + particleMass*(1.0 - 0.75*sqrte*z13);
151  return maxPairEnergy;
152}
153
154//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
155
156void G4MuPairProductionModel::Initialise(const G4ParticleDefinition* p,
157                                         const G4DataVector&)
158{ 
159  if (!samplingTablesAreFilled) {
160    if(p) SetParticle(p);
161    MakeSamplingTables();
162  }
163  if(!fParticleChange) fParticleChange = GetParticleChangeForLoss();
164}
165
166//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
167
168G4double G4MuPairProductionModel::ComputeDEDXPerVolume(
169                                              const G4Material* material,
170                                              const G4ParticleDefinition*,
171                                                    G4double kineticEnergy,
172                                                    G4double cutEnergy)
173{
174  G4double dedx = 0.0;
175  if (cutEnergy <= minPairEnergy || kineticEnergy <= lowestKinEnergy)
176    return dedx;
177
178  const G4ElementVector* theElementVector = material->GetElementVector();
179  const G4double* theAtomicNumDensityVector =
180                                   material->GetAtomicNumDensityVector();
181
182  //  loop for elements in the material
183  for (size_t i=0; i<material->GetNumberOfElements(); i++) {
184     G4double Z = (*theElementVector)[i]->GetZ();
185     SetCurrentElement(Z);
186     G4double tmax = MaxSecondaryEnergy(particle, kineticEnergy);
187     G4double loss = ComputMuPairLoss(Z, kineticEnergy, cutEnergy, tmax);
188     dedx += loss*theAtomicNumDensityVector[i];
189  }
190  if (dedx < 0.) dedx = 0.;
191  return dedx;
192}
193
194//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
195
196G4double G4MuPairProductionModel::ComputMuPairLoss(G4double Z, 
197                                                   G4double tkin,
198                                                   G4double cutEnergy, 
199                                                   G4double tmax)
200{
201  SetCurrentElement(Z);
202  G4double loss = 0.0;
203
204  G4double cut = std::min(cutEnergy,tmax);
205  if(cut <= minPairEnergy) return loss;
206
207  // calculate the rectricted loss
208  // numerical integration in log(PairEnergy)
209  G4double ak1=6.9;
210  G4double ak2=1.0;
211  G4double aaa = log(minPairEnergy);
212  G4double bbb = log(cut);
213  G4int    kkk = (G4int)((bbb-aaa)/ak1+ak2);
214  if (kkk > 8) kkk = 8;
215  G4double hhh = (bbb-aaa)/(G4double)kkk;
216  G4double x = aaa;
217
218  for (G4int l=0 ; l<kkk; l++)
219  {
220
221    for (G4int ll=0; ll<8; ll++)
222    {
223      G4double ep = exp(x+xgi[ll]*hhh);
224      loss += wgi[ll]*ep*ep*ComputeDMicroscopicCrossSection(tkin, Z, ep);
225    }
226    x += hhh;
227  }
228  loss *= hhh;
229  if (loss < 0.) loss = 0.;
230  return loss;
231}
232
233//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
234
235G4double G4MuPairProductionModel::ComputeMicroscopicCrossSection(
236                                           G4double tkin,
237                                           G4double Z,
238                                           G4double cut)
239{
240  G4double cross = 0.;
241  SetCurrentElement(Z);
242  G4double tmax = MaxSecondaryEnergy(particle, tkin);
243  if (tmax <= cut) return cross;
244
245  G4double ak1=6.9 ;
246  G4double ak2=1.0 ;
247  G4double aaa = log(cut);
248  G4double bbb = log(tmax);
249  G4int kkk = (G4int)((bbb-aaa)/ak1 + ak2);
250  if(kkk > 8) kkk = 8;
251  G4double hhh = (bbb-aaa)/float(kkk);
252  G4double x = aaa;
253
254  for(G4int l=0; l<kkk; l++)
255  {
256    for(G4int i=0; i<8; i++)
257    {
258      G4double ep = exp(x + xgi[i]*hhh);
259      cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
260    }
261    x += hhh;
262  }
263
264  cross *=hhh;
265  if(cross < 0.0) cross = 0.0;
266  return cross;
267}
268
269G4double G4MuPairProductionModel::ComputeDMicroscopicCrossSection(
270                                           G4double tkin,
271                                           G4double Z,
272                                           G4double pairEnergy)
273 // Calculates the  differential (D) microscopic cross section
274 // using the cross section formula of R.P. Kokoulin (18/01/98)
275 // Code modified by R.P. Kokoulin, V.N. Ivanchenko (27/01/04)
276{
277  G4double bbbtf= 183. ;
278  G4double bbbh = 202.4 ;
279  G4double g1tf = 1.95e-5 ;
280  G4double g2tf = 5.3e-5 ;
281  G4double g1h  = 4.4e-5 ;
282  G4double g2h  = 4.8e-5 ;
283
284  G4double totalEnergy  = tkin + particleMass;
285  G4double residEnergy  = totalEnergy - pairEnergy;
286  G4double massratio    = particleMass/electron_mass_c2 ;
287  G4double massratio2   = massratio*massratio ;
288  G4double cross = 0.;
289
290  SetCurrentElement(Z);
291
292  G4double c3 = 0.75*sqrte*particleMass;
293  if (residEnergy <= c3*z13) return cross;
294
295  G4double c7 = 4.*electron_mass_c2;
296  G4double c8 = 6.*particleMass*particleMass;
297  G4double alf = c7/pairEnergy;
298  G4double a3 = 1. - alf;
299  if (a3 <= 0.) return cross;
300
301  // zeta calculation
302  G4double bbb,g1,g2;
303  if( Z < 1.5 ) { bbb = bbbh ; g1 = g1h ; g2 = g2h ; }
304  else          { bbb = bbbtf; g1 = g1tf; g2 = g2tf; }
305
306  G4double zeta = 0;
307  G4double zeta1 = 0.073*log(totalEnergy/(particleMass+g1*z23*totalEnergy))-0.26;
308  if ( zeta1 > 0.)
309  {
310    G4double zeta2 = 0.058*log(totalEnergy/(particleMass+g2*z13*totalEnergy))-0.14;
311    zeta  = zeta1/zeta2 ;
312  }
313
314  G4double z2 = Z*(Z+zeta);
315  G4double screen0 = 2.*electron_mass_c2*sqrte*bbb/(z13*pairEnergy);
316  G4double a0 = totalEnergy*residEnergy;
317  G4double a1 = pairEnergy*pairEnergy/a0;
318  G4double bet = 0.5*a1;
319  G4double xi0 = 0.25*massratio2*a1;
320  G4double del = c8/a0;
321
322  G4double rta3 = sqrt(a3);
323  G4double tmnexp = alf/(1. + rta3) + del*rta3;
324  if(tmnexp >= 1.0) return cross;
325
326  G4double tmn = log(tmnexp);
327  G4double sum = 0.;
328
329  // Gaussian integration in ln(1-ro) ( with 8 points)
330  for (G4int i=0; i<8; i++)
331  {
332    G4double a4 = exp(tmn*xgi[i]);     // a4 = (1.-asymmetry)
333    G4double a5 = a4*(2.-a4) ;
334    G4double a6 = 1.-a5 ;
335    G4double a7 = 1.+a6 ;
336    G4double a9 = 3.+a6 ;
337    G4double xi = xi0*a5 ;
338    G4double xii = 1./xi ;
339    G4double xi1 = 1.+xi ;
340    G4double screen = screen0*xi1/a5 ;
341    G4double yeu = 5.-a6+4.*bet*a7 ;
342    G4double yed = 2.*(1.+3.*bet)*log(3.+xii)-a6-a1*(2.-a6) ;
343    G4double ye1 = 1.+yeu/yed ;
344    G4double ale=log(bbb/z13*sqrt(xi1*ye1)/(1.+screen*ye1)) ;
345    G4double cre = 0.5*log(1.+2.25*z23*xi1*ye1/massratio2) ;
346    G4double be;
347
348    if (xi <= 1.e3) be = ((2.+a6)*(1.+bet)+xi*a9)*log(1.+xii)+(a5-bet)/xi1-a9;
349    else            be = (3.-a6+a1*a7)/(2.*xi);
350
351    G4double fe = (ale-cre)*be;
352    if ( fe < 0.) fe = 0. ;
353
354    G4double ymu = 4.+a6 +3.*bet*a7 ;
355    G4double ymd = a7*(1.5+a1)*log(3.+xi)+1.-1.5*a6 ;
356    G4double ym1 = 1.+ymu/ymd ;
357    G4double alm_crm = log(bbb*massratio/(1.5*z23*(1.+screen*ym1)));
358    G4double a10,bm;
359    if ( xi >= 1.e-3)
360    {
361      a10 = (1.+a1)*a5 ;
362      bm  = (a7*(1.+1.5*bet)-a10*xii)*log(xi1)+xi*(a5-bet)/xi1+a10;
363    } else {
364      bm = (5.-a6+bet*a9)*(xi/2.);
365    }
366
367    G4double fm = alm_crm*bm;
368    if ( fm < 0.) fm = 0. ;
369
370    sum += wgi[i]*a4*(fe+fm/massratio2);
371  }
372
373  cross = -tmn*sum*factorForCross*z2*residEnergy/(totalEnergy*pairEnergy);
374
375  return cross;
376}
377
378//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
379
380G4double G4MuPairProductionModel::ComputeCrossSectionPerAtom(
381                                           const G4ParticleDefinition*,
382                                                 G4double kineticEnergy,
383                                                 G4double Z, G4double,
384                                                 G4double cutEnergy,
385                                                 G4double maxEnergy)
386{
387  G4double cross = 0.0;
388  if (kineticEnergy <= lowestKinEnergy) return cross;
389
390  SetCurrentElement(Z);
391
392  G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
393  G4double tmax = std::min(maxEnergy, maxPairEnergy);
394  G4double cut  = std::max(cutEnergy, minPairEnergy);
395  if (cut >= tmax) return cross;
396
397  cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut);
398  if(tmax < kineticEnergy) {
399    cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
400  }
401  return cross;
402}
403
404//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
405
406void G4MuPairProductionModel::MakeSamplingTables()
407{
408  for (G4int iz=0; iz<nzdat; iz++)
409  {
410    G4double Z = zdat[iz];
411    SetCurrentElement(Z);
412
413    for (G4int it=0; it<ntdat; it++) {
414
415      G4double kineticEnergy = tdat[it];
416      G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
417      // G4cout << "Z= " << currentZ << " z13= " << z13
418      //<< " mE= " << maxPairEnergy << G4endl;
419      G4double CrossSection = 0.0 ;
420
421      if(maxPairEnergy > minPairEnergy) {
422
423        G4double y = ymin - 0.5*dy ;
424        G4double yy = ymin - dy ;
425        G4double x = exp(y);
426        G4double fac = exp(dy);
427        G4double dx = exp(yy)*(fac - 1.0);
428
429        G4double c = log(maxPairEnergy/minPairEnergy);
430
431        for (G4int i=0 ; i<nbiny; i++) {
432          y += dy ;
433          if(c > 0.0) {
434            x *= fac;
435            dx*= fac;
436            G4double ep = minPairEnergy*exp(c*x) ;
437            CrossSection += 
438              ep*dx*ComputeDMicroscopicCrossSection(kineticEnergy, Z, ep);
439          }
440          ya[i] = y;
441          proba[iz][it][i] = CrossSection;
442        }
443       
444      } else {
445        for (G4int i=0 ; i<nbiny; i++) {
446          proba[iz][it][i] = CrossSection;
447        }
448      }
449
450      ya[nbiny]=ymax;
451      proba[iz][it][nbiny] = CrossSection;
452
453    }
454  }
455  samplingTablesAreFilled = true;
456}
457
458//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
459
460void 
461G4MuPairProductionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp, 
462                                           const G4MaterialCutsCouple* couple,
463                                           const G4DynamicParticle* aDynamicParticle,
464                                           G4double tmin,
465                                           G4double tmax)
466{
467  G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
468  G4double totalEnergy   = kineticEnergy + particleMass;
469  G4double totalMomentum = 
470    sqrt(kineticEnergy*(kineticEnergy + 2.0*particleMass));
471
472  G4ThreeVector partDirection = aDynamicParticle->GetMomentumDirection();
473
474  G4int it;
475  for(it=1; it<ntdat; ++it) {if(kineticEnergy <= tdat[it]) break;}
476  if(it == ntdat) { --it; }
477  G4double dt = log(kineticEnergy/tdat[it-1])/log(tdat[it]/tdat[it-1]);
478
479  // select randomly one element constituing the material
480  const G4Element* anElement = 
481    SelectRandomAtom(kineticEnergy, dt, it, couple, tmin);
482  SetCurrentElement(anElement->GetZ());
483
484  // define interval of enegry transfer
485  G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
486  G4double maxEnergy     = std::min(tmax, maxPairEnergy);
487  G4double minEnergy     = std::max(tmin, minPairEnergy);
488
489  if(minEnergy >= maxEnergy) { return; }
490  //G4cout << "emin= " << minEnergy << " emax= " << maxEnergy
491  //     << " minPair= " << minPairEnergy << " maxpair= " << maxPairEnergy
492  //       << " ymin= " << ymin << " dy= " << dy << G4endl;
493
494  // select bins
495  G4int iymin = 0;
496  G4int iymax = nbiny-1;
497  if( minEnergy > minPairEnergy)
498  {
499    G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
500    iymin = (G4int)((log(xc) - ymin)/dy);
501    if(iymin >= nbiny) iymin = nbiny-1;
502    else if(iymin < 0) iymin = 0;
503    xc = log(maxEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
504    iymax = (G4int)((log(xc) - ymin)/dy) + 1;
505    if(iymax >= nbiny) iymax = nbiny-1;
506    else if(iymax < 0) iymax = 0;
507  }
508
509  // sample e-e+ energy, pair energy first
510  G4int iz, iy;
511
512  for(iz=1; iz<nzdat; ++iz) { if(currentZ <= zdat[iz]) { break; } }
513  if(iz == nzdat) { --iz; }
514
515  G4double dz = log(currentZ/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
516
517  G4double pmin = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymin,currentZ);
518  G4double pmax = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymax,currentZ);
519
520  G4double p = pmin+G4UniformRand()*(pmax - pmin);
521
522  // interpolate sampling vector;
523  G4double p1 = pmin;
524  G4double p2 = pmin;
525  for(iy=iymin+1; iy<=iymax; ++iy) {
526    p1 = p2;
527    p2 = InterpolatedIntegralCrossSection(dt, dz, iz, it, iy, currentZ);
528    if(p <= p2) break;
529  }
530  // G4cout << "iy= " << iy << " iymin= " << iymin << " iymax= "
531  //        << iymax << " Z= " << currentZ << G4endl;
532  G4double y = ya[iy-1] + dy*(p - p1)/(p2 - p1);
533
534  G4double PairEnergy = minPairEnergy*exp(exp(y)
535                       *log(maxPairEnergy/minPairEnergy));
536                       
537  if(PairEnergy < minEnergy) { PairEnergy = minEnergy; }
538  if(PairEnergy > maxEnergy) { PairEnergy = maxEnergy; }
539
540  // sample r=(E+-E-)/PairEnergy  ( uniformly .....)
541  G4double rmax =
542    (1.-6.*particleMass*particleMass/(totalEnergy*(totalEnergy-PairEnergy)))
543                                       *sqrt(1.-minPairEnergy/PairEnergy);
544  G4double r = rmax * (-1.+2.*G4UniformRand()) ;
545
546  // compute energies from PairEnergy,r
547  G4double ElectronEnergy = (1.-r)*PairEnergy*0.5;
548  G4double PositronEnergy = PairEnergy - ElectronEnergy;
549
550  // The angle of the emitted virtual photon is sampled
551  // according to the muon bremsstrahlung model
552 
553  G4double gam  = totalEnergy/particleMass;
554  G4double gmax = gam*std::min(1.0, totalEnergy/PairEnergy - 1.0);
555  G4double gmax2= gmax*gmax;
556  G4double x = G4UniformRand()*gmax2/(1.0 + gmax2);
557
558  G4double theta = sqrt(x/(1.0 - x))/gam;
559  G4double sint  = sin(theta);
560  G4double phi   = twopi * G4UniformRand() ;
561  G4double dirx  = sint*cos(phi), diry = sint*sin(phi), dirz = cos(theta) ;
562
563  G4ThreeVector gDirection(dirx, diry, dirz);
564  gDirection.rotateUz(partDirection);
565
566  // the angles of e- and e+ assumed to be the same as virtual gamma
567
568  // create G4DynamicParticle object for the particle1
569  G4DynamicParticle* aParticle1 = 
570    new G4DynamicParticle(theElectron, gDirection, 
571                          ElectronEnergy - electron_mass_c2);
572
573  // create G4DynamicParticle object for the particle2
574  G4DynamicParticle* aParticle2 = 
575    new G4DynamicParticle(thePositron, gDirection,
576                          PositronEnergy - electron_mass_c2);
577
578  // primary change
579  kineticEnergy -= (ElectronEnergy + PositronEnergy);
580  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
581
582  partDirection *= totalMomentum;
583  partDirection -= (aParticle1->GetMomentum() + aParticle2->GetMomentum());
584  partDirection = partDirection.unit();
585  fParticleChange->SetProposedMomentumDirection(partDirection);
586
587  // add secondary
588  vdp->push_back(aParticle1);
589  vdp->push_back(aParticle2);
590}
591
592//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
593
594const G4Element* G4MuPairProductionModel::SelectRandomAtom(
595                 G4double kinEnergy, G4double dt, G4int it,
596           const G4MaterialCutsCouple* couple, G4double tmin)
597{
598  // select randomly 1 element within the material
599
600  const G4Material* material = couple->GetMaterial();
601  size_t nElements = material->GetNumberOfElements();
602  const G4ElementVector* theElementVector = material->GetElementVector();
603  if (nElements == 1) return (*theElementVector)[0];
604
605  if(nElements > nmaxElements) {
606    nmaxElements = nElements;
607    partialSum.resize(nmaxElements);
608  }
609
610  const G4double* theAtomNumDensityVector=material->GetAtomicNumDensityVector();
611
612  G4double sum = 0.0;
613  G4double dl;
614
615  size_t i;
616  for (i=0; i<nElements; i++) {
617    G4double Z = ((*theElementVector)[i])->GetZ();
618    SetCurrentElement(Z);
619    G4double maxPairEnergy = MaxSecondaryEnergy(particle,kinEnergy);
620    G4double minEnergy     = std::max(tmin, minPairEnergy);
621    dl = 0.0;
622    if(minEnergy < maxPairEnergy) {
623
624      G4int iz;
625      for(iz=1; iz<nzdat; iz++) {if(Z <= zdat[iz]) break;}
626      if(iz == nzdat) iz--;
627      G4double dz = log(Z/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
628
629      G4double sigcut;
630      if(minEnergy <= minPairEnergy)
631        sigcut = 0.;
632      else
633        {
634          G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
635          G4int iy = (G4int)((log(xc) - ymin)/dy);
636          if(iy < 0) iy = 0;
637          if(iy >= nbiny) iy = nbiny-1;
638          sigcut = InterpolatedIntegralCrossSection(dt,dz,iz,it,iy,   Z);
639        }
640
641      G4double sigtot = InterpolatedIntegralCrossSection(dt,dz,iz,it,nbiny,Z);
642      dl = (sigtot - sigcut)*theAtomNumDensityVector[i];
643    }
644    // protection
645    if(dl < 0.0) dl = 0.0;
646    sum += dl;
647    partialSum[i] = sum;
648  }
649
650  G4double rval = G4UniformRand()*sum;
651  for (i=0; i<nElements; i++) {
652    if(rval<=partialSum[i]) return (*theElementVector)[i];
653  }
654
655  return (*theElementVector)[nElements - 1];
656
657}
658
659//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
660
661
Note: See TracBrowser for help on using the repository browser.