source: trunk/source/processes/electromagnetic/highenergy/src/G4eeToHadronsModel.cc

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26// $Id: G4eeToHadronsModel.cc,v 1.10 2010/10/26 14:15:40 vnivanch Exp $
27// GEANT4 tag $Name: emhighenergy-V09-03-02 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class header file
32//
33//
34// File name:     G4eeToHadronsModel
35//
36// Author:        Vladimir Ivanchenko
37//
38// Creation date: 12.08.2003
39//
40// Modifications:
41// 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
42// 18-05-05 Use optimized interfaces (V.Ivantchenko)
43//
44//
45// -------------------------------------------------------------------
46//
47
48
49//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
50//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
51
52#include "G4eeToHadronsModel.hh"
53#include "Randomize.hh"
54#include "G4Electron.hh"
55#include "G4Gamma.hh"
56#include "G4Positron.hh"
57#include "G4PionPlus.hh"
58#include "Randomize.hh"
59#include "G4Vee2hadrons.hh"
60#include "G4PhysicsVector.hh"
61#include "G4PhysicsLogVector.hh"
62
63//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
64
65using namespace std;
66
67G4eeToHadronsModel::G4eeToHadronsModel(G4Vee2hadrons* m, G4int ver,
68                                       const G4String& nam)
69  : G4VEmModel(nam),
70    model(m),
71    crossPerElectron(0),
72    crossBornPerElectron(0),
73    isInitialised(false),
74    nbins(100),
75    verbose(ver)
76{
77  theGamma = G4Gamma::Gamma();
78  highKinEnergy = HighEnergyLimit();
79  lowKinEnergy  = LowEnergyLimit();
80  emin = lowKinEnergy;
81  emax = highKinEnergy;
82  peakKinEnergy = highKinEnergy;
83  epeak = emax;
84}
85
86//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
87
88G4eeToHadronsModel::~G4eeToHadronsModel()
89{
90  delete model;
91  delete crossPerElectron;
92  delete crossBornPerElectron;
93}
94
95//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
96
97void G4eeToHadronsModel::Initialise(const G4ParticleDefinition*,
98                                    const G4DataVector&)
99{
100  if(isInitialised) { return; }
101  isInitialised  = true;
102
103  // Lab system
104  highKinEnergy = HighEnergyLimit();
105  lowKinEnergy  = LowEnergyLimit();
106
107  // CM system
108  emin  = model->LowEnergy();
109  emax  = model->HighEnergy();
110
111  G4double emin0 = 
112    2.0*electron_mass_c2*sqrt(1.0 + 0.5*lowKinEnergy/electron_mass_c2);
113  G4double emax0 = 
114    2.0*electron_mass_c2*sqrt(1.0 + 0.5*highKinEnergy/electron_mass_c2);
115
116  // recompute low energy
117  if(emin0 > emax) {
118    emin0 = emax;
119    model->SetLowEnergy(emin0);
120  }
121  if(emin > emin0) {
122    emin0 = emin;
123    lowKinEnergy  = 0.5*emin*emin/electron_mass_c2 - 2.0*electron_mass_c2;
124    SetLowEnergyLimit(lowKinEnergy);
125  }
126
127  // recompute high energy
128  if(emax < emax0) {
129    emax0 = emax;
130    highKinEnergy = 0.5*emax*emax/electron_mass_c2 - 2.0*electron_mass_c2;
131    SetHighEnergyLimit(highKinEnergy);
132  }
133
134  // peak energy
135  epeak = std::min(model->PeakEnergy(), emax);
136  peakKinEnergy  = 0.5*epeak*epeak/electron_mass_c2 - 2.0*electron_mass_c2;
137
138  if(verbose>0) {
139    G4cout << "G4eeToHadronsModel::Initialise: " << G4endl;
140    G4cout << "LabSystem: emin(GeV)= " << lowKinEnergy/GeV
141           << " epeak(GeV)= " << peakKinEnergy/GeV
142           << " emax(GeV)= " << highKinEnergy/GeV
143           << G4endl;
144    G4cout << "SM System: emin(MeV)= " << emin/MeV
145           << " epeak(MeV)= " << epeak/MeV
146           << " emax(MeV)= " << emax/MeV
147           << G4endl;
148  }
149
150  if(lowKinEnergy < peakKinEnergy) {
151    crossBornPerElectron = model->PhysicsVector(emin, emax);
152    crossPerElectron     = model->PhysicsVector(emin, emax);
153    nbins = crossPerElectron->GetVectorLength();
154    for(G4int i=0; i<nbins; i++) {
155      G4double e  = crossPerElectron->GetLowEdgeEnergy(i);
156      G4double cs = model->ComputeCrossSection(e);
157      crossBornPerElectron->PutValue(i, cs);
158    }
159    ComputeCMCrossSectionPerElectron();
160  }
161  if(verbose>1) {
162    G4cout << "G4eeToHadronsModel: Cross secsions per electron"
163           << " nbins= " << nbins
164           << " emin(MeV)= " << emin/MeV
165           << " emax(MeV)= " << emax/MeV
166           << G4endl;
167    G4bool b;
168    for(G4int i=0; i<nbins; i++) {
169      G4double e  = crossPerElectron->GetLowEdgeEnergy(i);
170      G4double s1 = crossPerElectron->GetValue(e, b);
171      G4double s2 = crossBornPerElectron->GetValue(e, b);
172      G4cout << "E(MeV)= " << e/MeV
173             << "  cross(nb)= " << s1/nanobarn
174             << "  crossBorn(nb)= " << s2/nanobarn
175             << G4endl;
176    }
177  }
178}
179
180//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
181
182G4double G4eeToHadronsModel::CrossSectionPerVolume(
183                                      const G4Material* mat,
184                                      const G4ParticleDefinition* p,
185                                      G4double kineticEnergy,
186                                      G4double, G4double)
187{
188  return mat->GetElectronDensity()*
189    ComputeCrossSectionPerElectron(p, kineticEnergy);
190}
191
192//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
193
194G4double G4eeToHadronsModel::ComputeCrossSectionPerAtom(
195                                      const G4ParticleDefinition* p,
196                                      G4double kineticEnergy,
197                                      G4double Z, G4double,
198                                      G4double, G4double)
199{
200  return Z*ComputeCrossSectionPerElectron(p, kineticEnergy);
201}
202
203//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
204
205G4double G4eeToHadronsModel::ComputeCrossSectionPerElectron(
206                                          const G4ParticleDefinition*,
207                                                G4double kineticEnergy,
208                                                G4double, G4double)
209{
210  G4double cross = 0.0;
211  if(crossPerElectron) {
212    G4bool b;
213    G4double e = 2.0*electron_mass_c2*
214                 sqrt(1.0 + 0.5*kineticEnergy/electron_mass_c2);
215    cross = crossPerElectron->GetValue(e, b);
216  }
217  //  G4cout << "e= " << kineticEnergy << " cross= " << cross << G4endl;
218  return cross;
219}
220
221//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
222
223void G4eeToHadronsModel::SampleSecondaries(std::vector<G4DynamicParticle*>* newp,
224                                           const G4MaterialCutsCouple*,
225                                           const G4DynamicParticle* dParticle,
226                                           G4double,
227                                           G4double)
228{
229  if(crossPerElectron) {
230    G4double t = dParticle->GetKineticEnergy();
231    G4double e = 2.0*electron_mass_c2*sqrt(1.0 + 0.5*t/electron_mass_c2);
232    G4LorentzVector inlv = dParticle->Get4Momentum();
233    G4ThreeVector inBoost = inlv.boostVector();
234    if(e > emin) {
235      G4DynamicParticle* gamma = GenerateCMPhoton(e);
236      G4LorentzVector gLv = gamma->Get4Momentum();
237      G4LorentzVector lv(0.0,0.0,0.0,e);
238      lv -= gLv;
239      G4double m = lv.m();
240      G4ThreeVector boost = lv.boostVector();
241      const G4ThreeVector dir = gamma->GetMomentumDirection();
242      model->SampleSecondaries(newp, m, dir);
243      G4int np = newp->size();
244      for(G4int j=0; j<np; j++) {
245        G4DynamicParticle* dp = (*newp)[j];
246        G4LorentzVector v = dp->Get4Momentum();
247        v.boost(boost);
248        v.boost(inBoost);
249        dp->Set4Momentum(v);
250      }
251      gLv.boost(inBoost);
252      gamma->Set4Momentum(gLv);
253      newp->push_back(gamma);
254    }
255  }
256}
257
258//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
259
260void G4eeToHadronsModel::ComputeCMCrossSectionPerElectron()
261{
262  G4bool b;
263  for(G4int i=0; i<nbins; i++) {
264    G4double e  = crossPerElectron->GetLowEdgeEnergy(i);
265    G4double cs = 0.0;
266    if(i > 0) {
267      G4double L   = 2.0*log(e/electron_mass_c2);
268      G4double bt  = 2.0*fine_structure_const*(L - 1.0)/pi;
269      G4double btm1= bt - 1.0;
270      G4double del = 1. + fine_structure_const*(1.5*L + pi*pi/3. -2.)/pi;
271      G4double s1  = crossBornPerElectron->GetValue(e, b);
272      G4double e1  = crossPerElectron->GetLowEdgeEnergy(i-1);
273      G4double x1  = 1. - e1/e;
274      cs += s1*(del*pow(x1,bt) - bt*(x1 - 0.25*x1*x1));
275      if(i > 1) {
276        G4double e2  = e1;
277        G4double x2  = x1;
278        G4double s2  = crossBornPerElectron->GetValue(e2, b);
279        G4double w2  = bt*(del*pow(x2,btm1) - 1.0 + 0.5*x2);
280     
281        for(G4int j=i-2; j>=0; j--) {
282          e1  = crossPerElectron->GetLowEdgeEnergy(j);
283          x1  = 1. - e1/e;
284          G4double s1 = crossBornPerElectron->GetValue(e1, b);
285          G4double w1 = bt*(del*pow(x1,btm1) - 1.0 + 0.5*x1);
286          cs += 0.5*(x1 - x2)*(w2*s2 + w1*s1);
287          e2 = e1;
288          x2 = x1;
289          s2 = s1;
290          w2 = w1;
291        }
292      }
293    }
294    crossPerElectron->PutValue(i, cs);
295    //    G4cout << "e= " << e << "  cs= " << cs << G4endl;
296  }
297}
298
299//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
300
301G4DynamicParticle* G4eeToHadronsModel::GenerateCMPhoton(G4double e)
302{
303  G4bool b;   
304  G4double x;
305  G4DynamicParticle* gamma = 0;
306  G4double L   = 2.0*log(e/electron_mass_c2);
307  G4double bt  = 2.0*fine_structure_const*(L - 1.)/pi;
308  G4double btm1= bt - 1.0;
309  G4double del = 1. + fine_structure_const*(1.5*L + pi*pi/3. -2.)/pi;
310
311  G4double s0 = crossBornPerElectron->GetValue(e, b);
312  G4double de = (emax - emin)/(G4double)nbins;
313  G4double x0 = min(de,e - emin)/e;
314  G4double ds = crossBornPerElectron->GetValue(e, b)
315              *(del*pow(x0,bt) - bt*(x0 - 0.25*x0*x0));
316  G4double e1 = e*(1. - x0);
317
318  if(e1 < emax && s0*G4UniformRand()<ds) { 
319    x = x0*pow(G4UniformRand(),1./bt);
320  } else {   
321
322    x  = 1. - e1/e;
323    G4double s1 = crossBornPerElectron->GetValue(e1, b);
324    G4double w1 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
325    G4double grej = s1*w1;
326    G4double f;
327    //    G4cout << "e= " << e/GeV << " epeak= " << epeak/GeV
328    //       << " s1= " << s1 << " w1= " << w1
329    //       << " grej= " << grej << G4endl;
330    // Above emax cross section is 0
331    if(e1 > emax) {
332      x  = 1. - emax/e;
333      G4double s2 = crossBornPerElectron->GetValue(emax, b);
334      G4double w2 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
335      grej = s2*w2;
336      //  G4cout << "emax= " << emax << " s2= " << s2 << " w2= " << w2
337      //   << " grej= " << grej << G4endl;
338    }
339
340    if(e1 > epeak) {
341      x  = 1. - epeak/e;
342      G4double s2 = crossBornPerElectron->GetValue(epeak, b);
343      G4double w2 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
344      grej = max(grej,s2*w2);
345      //G4cout << "epeak= " << epeak << " s2= " << s2 << " w2= " << w2
346      //     << " grej= " << grej << G4endl;
347    }
348    G4double xmin = 1. - e1/e;
349    if(e1 > emax) xmin = 1. - emax/e;
350    G4double xmax = 1. - emin/e;
351    do {
352      x = xmin + G4UniformRand()*(xmax - xmin);
353      G4double s2 = crossBornPerElectron->GetValue((1.0 - x)*e, b);
354      G4double w2 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
355      //G4cout << "x= " << x << " xmin= " << xmin << " xmax= " << xmax
356      //     << " s2= " << s2 << " w2= " << w2
357      //           << G4endl;
358      f = s2*w2;
359      if(f > grej) {
360        G4cout << "G4DynamicParticle* G4eeToHadronsModel:WARNING "
361               << f << " > " << grej << " majorant is`small!" 
362               << G4endl; 
363      }
364    } while (f < grej*G4UniformRand());
365  }
366
367  G4ThreeVector dir(0.0,0.0,1.0);
368  gamma = new G4DynamicParticle(theGamma,dir,x*e);
369  return gamma;
370}
371
372//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
373
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