source: trunk/source/processes/electromagnetic/muons/src/G4MuPairProductionModel.cc @ 989

Last change on this file since 989 was 961, checked in by garnier, 15 years ago

update processes
File size: 22.0 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 1.40 2009/02/20 14:48:16 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-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
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) {
164    if(pParticleChange) 
165      fParticleChange = 
166        reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
167    else 
168      fParticleChange = new G4ParticleChangeForLoss();
169  }
170}
171
172//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
173
174G4double G4MuPairProductionModel::ComputeDEDXPerVolume(
175                                              const G4Material* material,
176                                              const G4ParticleDefinition*,
177                                                    G4double kineticEnergy,
178                                                    G4double cutEnergy)
179{
180  G4double dedx = 0.0;
181  if (cutEnergy <= minPairEnergy || kineticEnergy <= lowestKinEnergy)
182    return dedx;
183
184  const G4ElementVector* theElementVector = material->GetElementVector();
185  const G4double* theAtomicNumDensityVector =
186                                   material->GetAtomicNumDensityVector();
187
188  //  loop for elements in the material
189  for (size_t i=0; i<material->GetNumberOfElements(); i++) {
190     G4double Z = (*theElementVector)[i]->GetZ();
191     SetCurrentElement(Z);
192     G4double tmax = MaxSecondaryEnergy(particle, kineticEnergy);
193     G4double loss = ComputMuPairLoss(Z, kineticEnergy, cutEnergy, tmax);
194     dedx += loss*theAtomicNumDensityVector[i];
195  }
196  if (dedx < 0.) dedx = 0.;
197  return dedx;
198}
199
200//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
201
202G4double G4MuPairProductionModel::ComputMuPairLoss(G4double Z, 
203                                                   G4double tkin,
204                                                   G4double cutEnergy, 
205                                                   G4double tmax)
206{
207  SetCurrentElement(Z);
208  G4double loss = 0.0;
209
210  G4double cut = std::min(cutEnergy,tmax);
211  if(cut <= minPairEnergy) return loss;
212
213  // calculate the rectricted loss
214  // numerical integration in log(PairEnergy)
215  G4double ak1=6.9;
216  G4double ak2=1.0;
217  G4double aaa = log(minPairEnergy);
218  G4double bbb = log(cut);
219  G4int    kkk = (G4int)((bbb-aaa)/ak1+ak2);
220  if (kkk > 8) kkk = 8;
221  G4double hhh = (bbb-aaa)/(G4double)kkk;
222  G4double x = aaa;
223
224  for (G4int l=0 ; l<kkk; l++)
225  {
226
227    for (G4int ll=0; ll<8; ll++)
228    {
229      G4double ep = exp(x+xgi[ll]*hhh);
230      loss += wgi[ll]*ep*ep*ComputeDMicroscopicCrossSection(tkin, Z, ep);
231    }
232    x += hhh;
233  }
234  loss *= hhh;
235  if (loss < 0.) loss = 0.;
236  return loss;
237}
238
239//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
240
241G4double G4MuPairProductionModel::ComputeMicroscopicCrossSection(
242                                           G4double tkin,
243                                           G4double Z,
244                                           G4double cut)
245{
246  G4double cross = 0.;
247  SetCurrentElement(Z);
248  G4double tmax = MaxSecondaryEnergy(particle, tkin);
249  if (tmax <= cut) return cross;
250
251  G4double ak1=6.9 ;
252  G4double ak2=1.0 ;
253  G4double aaa = log(cut);
254  G4double bbb = log(tmax);
255  G4int kkk = (G4int)((bbb-aaa)/ak1 + ak2);
256  if(kkk > 8) kkk = 8;
257  G4double hhh = (bbb-aaa)/float(kkk);
258  G4double x = aaa;
259
260  for(G4int l=0; l<kkk; l++)
261  {
262    for(G4int i=0; i<8; i++)
263    {
264      G4double ep = exp(x + xgi[i]*hhh);
265      cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
266    }
267    x += hhh;
268  }
269
270  cross *=hhh;
271  if(cross < 0.0) cross = 0.0;
272  return cross;
273}
274
275G4double G4MuPairProductionModel::ComputeDMicroscopicCrossSection(
276                                           G4double tkin,
277                                           G4double Z,
278                                           G4double pairEnergy)
279 // Calculates the  differential (D) microscopic cross section
280 // using the cross section formula of R.P. Kokoulin (18/01/98)
281 // Code modified by R.P. Kokoulin, V.N. Ivanchenko (27/01/04)
282{
283  G4double bbbtf= 183. ;
284  G4double bbbh = 202.4 ;
285  G4double g1tf = 1.95e-5 ;
286  G4double g2tf = 5.3e-5 ;
287  G4double g1h  = 4.4e-5 ;
288  G4double g2h  = 4.8e-5 ;
289
290  G4double totalEnergy  = tkin + particleMass;
291  G4double residEnergy  = totalEnergy - pairEnergy;
292  G4double massratio    = particleMass/electron_mass_c2 ;
293  G4double massratio2   = massratio*massratio ;
294  G4double cross = 0.;
295
296  SetCurrentElement(Z);
297
298  G4double c3 = 0.75*sqrte*particleMass;
299  if (residEnergy <= c3*z13) return cross;
300
301  G4double c7 = 4.*electron_mass_c2;
302  G4double c8 = 6.*particleMass*particleMass;
303  G4double alf = c7/pairEnergy;
304  G4double a3 = 1. - alf;
305  if (a3 <= 0.) return cross;
306
307  // zeta calculation
308  G4double bbb,g1,g2;
309  if( Z < 1.5 ) { bbb = bbbh ; g1 = g1h ; g2 = g2h ; }
310  else          { bbb = bbbtf; g1 = g1tf; g2 = g2tf; }
311
312  G4double zeta = 0;
313  G4double zeta1 = 0.073*log(totalEnergy/(particleMass+g1*z23*totalEnergy))-0.26;
314  if ( zeta1 > 0.)
315  {
316    G4double zeta2 = 0.058*log(totalEnergy/(particleMass+g2*z13*totalEnergy))-0.14;
317    zeta  = zeta1/zeta2 ;
318  }
319
320  G4double z2 = Z*(Z+zeta);
321  G4double screen0 = 2.*electron_mass_c2*sqrte*bbb/(z13*pairEnergy);
322  G4double a0 = totalEnergy*residEnergy;
323  G4double a1 = pairEnergy*pairEnergy/a0;
324  G4double bet = 0.5*a1;
325  G4double xi0 = 0.25*massratio2*a1;
326  G4double del = c8/a0;
327
328  G4double rta3 = sqrt(a3);
329  G4double tmnexp = alf/(1. + rta3) + del*rta3;
330  if(tmnexp >= 1.0) return cross;
331
332  G4double tmn = log(tmnexp);
333  G4double sum = 0.;
334
335  // Gaussian integration in ln(1-ro) ( with 8 points)
336  for (G4int i=0; i<8; i++)
337  {
338    G4double a4 = exp(tmn*xgi[i]);     // a4 = (1.-asymmetry)
339    G4double a5 = a4*(2.-a4) ;
340    G4double a6 = 1.-a5 ;
341    G4double a7 = 1.+a6 ;
342    G4double a9 = 3.+a6 ;
343    G4double xi = xi0*a5 ;
344    G4double xii = 1./xi ;
345    G4double xi1 = 1.+xi ;
346    G4double screen = screen0*xi1/a5 ;
347    G4double yeu = 5.-a6+4.*bet*a7 ;
348    G4double yed = 2.*(1.+3.*bet)*log(3.+xii)-a6-a1*(2.-a6) ;
349    G4double ye1 = 1.+yeu/yed ;
350    G4double ale=log(bbb/z13*sqrt(xi1*ye1)/(1.+screen*ye1)) ;
351    G4double cre = 0.5*log(1.+2.25*z23*xi1*ye1/massratio2) ;
352    G4double be;
353
354    if (xi <= 1.e3) be = ((2.+a6)*(1.+bet)+xi*a9)*log(1.+xii)+(a5-bet)/xi1-a9;
355    else            be = (3.-a6+a1*a7)/(2.*xi);
356
357    G4double fe = (ale-cre)*be;
358    if ( fe < 0.) fe = 0. ;
359
360    G4double ymu = 4.+a6 +3.*bet*a7 ;
361    G4double ymd = a7*(1.5+a1)*log(3.+xi)+1.-1.5*a6 ;
362    G4double ym1 = 1.+ymu/ymd ;
363    G4double alm_crm = log(bbb*massratio/(1.5*z23*(1.+screen*ym1)));
364    G4double a10,bm;
365    if ( xi >= 1.e-3)
366    {
367      a10 = (1.+a1)*a5 ;
368      bm  = (a7*(1.+1.5*bet)-a10*xii)*log(xi1)+xi*(a5-bet)/xi1+a10;
369    } else {
370      bm = (5.-a6+bet*a9)*(xi/2.);
371    }
372
373    G4double fm = alm_crm*bm;
374    if ( fm < 0.) fm = 0. ;
375
376    sum += wgi[i]*a4*(fe+fm/massratio2);
377  }
378
379  cross = -tmn*sum*factorForCross*z2*residEnergy/(totalEnergy*pairEnergy);
380
381  return cross;
382}
383
384//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
385
386G4double G4MuPairProductionModel::ComputeCrossSectionPerAtom(
387                                           const G4ParticleDefinition*,
388                                                 G4double kineticEnergy,
389                                                 G4double Z, G4double,
390                                                 G4double cutEnergy,
391                                                 G4double maxEnergy)
392{
393  G4double cross = 0.0;
394  if (kineticEnergy <= lowestKinEnergy) return cross;
395
396  SetCurrentElement(Z);
397  G4double tmax = std::min(maxEnergy, kineticEnergy);
398  G4double cut  = std::min(cutEnergy, kineticEnergy);
399  if(cut < minPairEnergy) cut = minPairEnergy;
400  if (cut >= tmax) return cross;
401
402  cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut);
403  if(tmax < kineticEnergy) {
404    cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
405  }
406  return cross;
407}
408
409//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
410
411void G4MuPairProductionModel::MakeSamplingTables()
412{
413  for (G4int iz=0; iz<nzdat; iz++)
414  {
415    G4double Z = zdat[iz];
416    SetCurrentElement(Z);
417
418    for (G4int it=0; it<ntdat; it++) {
419
420      G4double kineticEnergy = tdat[it];
421      G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
422      // G4cout << "Z= " << currentZ << " z13= " << z13
423      //<< " mE= " << maxPairEnergy << G4endl;
424      G4double CrossSection = 0.0 ;
425
426      if(maxPairEnergy > minPairEnergy) {
427
428        G4double y = ymin - 0.5*dy ;
429        G4double yy = ymin - dy ;
430        G4double x = exp(y);
431        G4double fac = exp(dy);
432        G4double dx = exp(yy)*(fac - 1.0);
433
434        G4double c = log(maxPairEnergy/minPairEnergy);
435
436        for (G4int i=0 ; i<nbiny; i++) {
437          y += dy ;
438          if(c > 0.0) {
439            x *= fac;
440            dx*= fac;
441            G4double ep = minPairEnergy*exp(c*x) ;
442            CrossSection += 
443              ep*dx*ComputeDMicroscopicCrossSection(kineticEnergy, Z, ep);
444          }
445          ya[i] = y;
446          proba[iz][it][i] = CrossSection;
447        }
448       
449      } else {
450        for (G4int i=0 ; i<nbiny; i++) {
451          proba[iz][it][i] = CrossSection;
452        }
453      }
454
455      ya[nbiny]=ymax;
456      proba[iz][it][nbiny] = CrossSection;
457
458    }
459  }
460  samplingTablesAreFilled = true;
461}
462
463//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
464
465void G4MuPairProductionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp, 
466                                                const G4MaterialCutsCouple* couple,
467                                                const G4DynamicParticle* aDynamicParticle,
468                                                G4double tmin,
469                                                G4double tmax)
470{
471  G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
472  G4double totalEnergy   = kineticEnergy + particleMass ;
473  G4ParticleMomentum ParticleDirection = 
474    aDynamicParticle->GetMomentumDirection();
475
476  G4int it;
477  for(it=1; it<ntdat; it++) {if(kineticEnergy <= tdat[it]) break;}
478  if(it == ntdat) it--;
479  G4double dt = log(kineticEnergy/tdat[it-1])/log(tdat[it]/tdat[it-1]);
480
481  // select randomly one element constituing the material
482  const G4Element* anElement = SelectRandomAtom(kineticEnergy, dt, it, couple, tmin);
483  SetCurrentElement(anElement->GetZ());
484
485  // define interval of enegry transfer
486  G4double maxPairEnergy = MaxSecondaryEnergy(particle,kineticEnergy);
487  G4double maxEnergy     = std::min(tmax, maxPairEnergy);
488  G4double minEnergy     = std::max(tmin, minPairEnergy);
489
490  if(minEnergy >= maxEnergy) return;
491  //G4cout << "emin= " << minEnergy << " emax= " << maxEnergy
492  //     << " minPair= " << minPairEnergy << " maxpair= " << maxPairEnergy
493  //       << " ymin= " << ymin << " dy= " << dy << G4endl;
494
495  // select bins
496  G4int iymin = 0;
497  G4int iymax = nbiny-1;
498  if( minEnergy > minPairEnergy)
499  {
500    G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
501    iymin = (G4int)((log(xc) - ymin)/dy);
502    if(iymin >= nbiny) iymin = nbiny-1;
503    else if(iymin < 0) iymin = 0;
504    xc = log(maxEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
505    iymax = (G4int)((log(xc) - ymin)/dy) + 1;
506    if(iymax >= nbiny) iymax = nbiny-1;
507    else if(iymax < 0) iymax = 0;
508  }
509
510  // sample e-e+ energy, pair energy first
511  G4int iz, iy;
512
513  for(iz=1; iz<nzdat; iz++) {if(currentZ <= zdat[iz]) break;}
514  if(iz == nzdat) iz--;
515
516  G4double dz = log(currentZ/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
517
518  G4double pmin = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymin,currentZ);
519  G4double pmax = InterpolatedIntegralCrossSection(dt,dz,iz,it,iymax,currentZ);
520
521  G4double p = pmin+G4UniformRand()*(pmax - pmin);
522
523  // interpolate sampling vector;
524  G4double p1 = pmin;
525  G4double p2 = pmin;
526  for(iy=iymin+1; iy<=iymax; iy++) {
527    p1 = p2;
528    p2 = InterpolatedIntegralCrossSection(dt, dz, iz, it, iy, currentZ);
529    if(p <= p2) break;
530  }
531  // G4cout << "iy= " << iy << " iymin= " << iymin << " iymax= "
532  //        << iymax << " Z= " << currentZ << G4endl;
533  G4double y = ya[iy-1] + dy*(p - p1)/(p2 - p1);
534
535  G4double PairEnergy = minPairEnergy*exp(exp(y)
536                       *log(maxPairEnergy/minPairEnergy));
537                       
538  if(PairEnergy < minEnergy) PairEnergy = minEnergy;
539  if(PairEnergy > maxEnergy) PairEnergy = maxEnergy;
540
541  // sample r=(E+-E-)/PairEnergy  ( uniformly .....)
542  G4double rmax =
543    (1.-6.*particleMass*particleMass/(totalEnergy*(totalEnergy-PairEnergy)))
544                                       *sqrt(1.-minPairEnergy/PairEnergy);
545  G4double r = rmax * (-1.+2.*G4UniformRand()) ;
546
547  // compute energies from PairEnergy,r
548  G4double ElectronEnergy = (1.-r)*PairEnergy*0.5;
549  G4double PositronEnergy = PairEnergy - ElectronEnergy;
550
551  //  angles of the emitted particles ( Z - axis along the parent particle)
552  //      (mean theta for the moment)
553
554  //
555  // scattered electron (positron) angles. ( Z - axis along the parent photon)
556  //
557  //  universal distribution suggested by L. Urban
558  // (Geant3 manual (1993) Phys211),
559  //  derived from Tsai distribution (Rev Mod Phys 49,421(1977))
560  //  G4cout << "Ee= " << ElectronEnergy << " Ep= " << PositronEnergy << G4endl;
561  G4double u;
562  const G4double a1 = 0.625 , a2 = 3.*a1 , d = 27. ;
563
564  if (9./(9.+d) >G4UniformRand()) u= - log(G4UniformRand()*G4UniformRand())/a1;
565  else                            u= - log(G4UniformRand()*G4UniformRand())/a2;
566
567  G4double TetEl = u*electron_mass_c2/ElectronEnergy;
568  G4double TetPo = u*electron_mass_c2/PositronEnergy;
569  G4double Phi  = twopi * G4UniformRand();
570  G4double dxEl= sin(TetEl)*cos(Phi),dyEl= sin(TetEl)*sin(Phi),dzEl=cos(TetEl);
571  G4double dxPo=-sin(TetPo)*cos(Phi),dyPo=-sin(TetPo)*sin(Phi),dzPo=cos(TetPo);
572
573  G4ThreeVector ElectDirection (dxEl, dyEl, dzEl);
574  ElectDirection.rotateUz(ParticleDirection);
575
576  // create G4DynamicParticle object for the particle1
577  G4DynamicParticle* aParticle1= new G4DynamicParticle(theElectron,
578                                                       ElectDirection,
579                                             ElectronEnergy - electron_mass_c2);
580
581  G4ThreeVector PositDirection (dxPo, dyPo, dzPo);
582  PositDirection.rotateUz(ParticleDirection);
583
584  // create G4DynamicParticle object for the particle2
585  G4DynamicParticle* aParticle2 = 
586    new G4DynamicParticle(thePositron,
587                          PositDirection,
588                          PositronEnergy - electron_mass_c2);
589
590  // primary change
591  kineticEnergy -= (ElectronEnergy + PositronEnergy);
592  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
593
594  vdp->push_back(aParticle1);
595  vdp->push_back(aParticle2);
596}
597
598//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
599
600const G4Element* G4MuPairProductionModel::SelectRandomAtom(
601                 G4double kinEnergy, G4double dt, G4int it,
602           const G4MaterialCutsCouple* couple, G4double tmin)
603{
604  // select randomly 1 element within the material
605
606  const G4Material* material = couple->GetMaterial();
607  size_t nElements = material->GetNumberOfElements();
608  const G4ElementVector* theElementVector = material->GetElementVector();
609  if (nElements == 1) return (*theElementVector)[0];
610
611  if(nElements > nmaxElements) {
612    nmaxElements = nElements;
613    partialSum.resize(nmaxElements);
614  }
615
616  const G4double* theAtomNumDensityVector=material->GetAtomicNumDensityVector();
617
618  G4double sum = 0.0;
619
620  size_t i;
621  for (i=0; i<nElements; i++) {
622    G4double Z = ((*theElementVector)[i])->GetZ();
623    SetCurrentElement(Z);
624    G4double maxPairEnergy = MaxSecondaryEnergy(particle,kinEnergy);
625    G4double minEnergy     = std::max(tmin, minPairEnergy);
626
627    G4int iz;
628    for(iz=1; iz<nzdat; iz++) {if(Z <= zdat[iz]) break;}
629    if(iz == nzdat) iz--;
630    G4double dz = log(Z/zdat[iz-1])/log(zdat[iz]/zdat[iz-1]);
631
632    G4double sigcut;
633    if(minEnergy <= minPairEnergy)
634      sigcut = 0.;
635    else
636    {
637      G4double xc = log(minEnergy/minPairEnergy)/log(maxPairEnergy/minPairEnergy);
638      G4int iy = (G4int)((log(xc) - ymin)/dy);
639      if(iy < 0) iy = 0;
640      if(iy >= nbiny) iy = nbiny-1;
641      sigcut = InterpolatedIntegralCrossSection(dt,dz,iz,it,iy,   Z);
642    }
643
644    G4double sigtot = InterpolatedIntegralCrossSection(dt,dz,iz,it,nbiny,Z);
645    G4double dl = (sigtot - sigcut)*theAtomNumDensityVector[i];
646
647    // protection
648    if(dl < 0.0) dl = 0.0;
649    sum += dl;
650    partialSum[i] = sum;
651  }
652
653  G4double rval = G4UniformRand()*sum;
654  for (i=0; i<nElements; i++) {
655    if(rval<=partialSum[i]) return (*theElementVector)[i];
656  }
657
658  return (*theElementVector)[nElements - 1];
659
660}
661
662//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
663
664
Note: See TracBrowser for help on using the repository browser.