source: trunk/source/processes/electromagnetic/highenergy/src/G4eeToHadronsModel.cc @ 846

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26// $Id: G4eeToHadronsModel.cc,v 1.8 2007/05/22 17:37:30 vnivanch Exp $
27// GEANT4 tag $Name:  $
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(const G4Vee2hadrons* m,
68                                             G4int ver,
69                                       const G4String& nam)
70  : G4VEmModel(nam),
71  model(m),
72  crossPerElectron(0),
73  crossBornPerElectron(0),
74  isInitialised(false),
75  nbins(100),
76  verbose(ver)
77{
78  theGamma      = G4Gamma::Gamma();
79}
80
81//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
82
83G4eeToHadronsModel::~G4eeToHadronsModel()
84{
85  delete model;
86  delete crossPerElectron;
87  delete crossBornPerElectron;
88}
89
90//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
91
92void G4eeToHadronsModel::Initialise(const G4ParticleDefinition*,
93                                    const G4DataVector&)
94{
95  if(isInitialised) return;
96  isInitialised  = true;
97
98  highKinEnergy = HighEnergyLimit();
99  lowKinEnergy  = LowEnergyLimit();
100
101  emin  = model->ThresholdEnergy();
102  emax = 2.0*electron_mass_c2*sqrt(1.0 + 0.5*highKinEnergy/electron_mass_c2);
103  if(emin > emax) emin = emax;
104
105  lowKinEnergy  = 0.5*emin*emin/electron_mass_c2 - 2.0*electron_mass_c2;
106
107  epeak = min(model->PeakEnergy(), emax);
108  peakKinEnergy  = 0.5*epeak*epeak/electron_mass_c2 - 2.0*electron_mass_c2;
109
110  if(verbose>0) {
111    G4cout << "G4eeToHadronsModel::Initialise: " << G4endl;
112    G4cout << "LabSystem: emin(GeV)= " << lowKinEnergy/GeV
113           << " epeak(GeV)= " << peakKinEnergy/GeV
114           << " emax(GeV)= " << highKinEnergy/GeV
115           << G4endl;
116    G4cout << "SM System: emin(MeV)= " << emin/MeV
117           << " epeak(MeV)= " << epeak/MeV
118           << " emax(MeV)= " << emax/MeV
119           << G4endl;
120  }
121
122  if(lowKinEnergy < peakKinEnergy) {
123    crossBornPerElectron = model->PhysicsVector(emin, emax);
124    crossPerElectron     = model->PhysicsVector(emin, emax);
125    nbins = crossPerElectron->GetVectorLength();
126    for(G4int i=0; i<nbins; i++) {
127      G4double e  = crossPerElectron->GetLowEdgeEnergy(i);
128      G4double cs = model->ComputeCrossSection(e);
129      crossBornPerElectron->PutValue(i, cs);
130    }
131    ComputeCMCrossSectionPerElectron();
132  }
133  if(verbose>1) {
134    G4cout << "G4eeToHadronsModel: Cross secsions per electron"
135           << " nbins= " << nbins
136           << " emin(MeV)= " << emin/MeV
137           << " emax(MeV)= " << emax/MeV
138           << G4endl;
139    G4bool b;
140    for(G4int i=0; i<nbins; i++) {
141      G4double e  = crossPerElectron->GetLowEdgeEnergy(i);
142      G4double s1 = crossPerElectron->GetValue(e, b);
143      G4double s2 = crossBornPerElectron->GetValue(e, b);
144      G4cout << "E(MeV)= " << e/MeV
145             << "  cross(nb)= " << s1/nanobarn
146             << "  crossBorn(nb)= " << s2/nanobarn
147             << G4endl;
148    }
149  }
150}
151
152//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
153
154G4double G4eeToHadronsModel::ComputeCrossSectionPerElectron(
155                                          const G4ParticleDefinition*,
156                                                G4double kineticEnergy,
157                                                G4double, G4double)
158{
159  G4double cross = 0.0;
160  if(crossPerElectron) {
161    G4bool b;
162    G4double e = 2.0*electron_mass_c2*
163                 sqrt(1.0 + 0.5*kineticEnergy/electron_mass_c2);
164    cross = crossPerElectron->GetValue(e, b);
165  }
166  //  G4cout << "e= " << kineticEnergy << " cross= " << cross << G4endl;
167  return cross;
168}
169
170//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
171
172void G4eeToHadronsModel::SampleSecondaries(std::vector<G4DynamicParticle*>* newp,
173                                           const G4MaterialCutsCouple*,
174                                           const G4DynamicParticle* dParticle,
175                                           G4double,
176                                           G4double)
177{
178  if(crossPerElectron) {
179    G4double t = dParticle->GetKineticEnergy();
180    G4double e = 2.0*electron_mass_c2*sqrt(1.0 + 0.5*t/electron_mass_c2);
181    G4LorentzVector inlv = dParticle->Get4Momentum();
182    G4ThreeVector inBoost = inlv.boostVector();
183    if(e > emin) {
184      G4DynamicParticle* gamma = GenerateCMPhoton(e);
185      G4LorentzVector gLv = gamma->Get4Momentum();
186      G4LorentzVector lv(0.0,0.0,0.0,e);
187      lv -= gLv;
188      G4double m = lv.m();
189      G4ThreeVector boost = lv.boostVector();
190      const G4ThreeVector dir = gamma->GetMomentumDirection();
191      model->SampleSecondaries(newp, m, dir);
192      G4int np = newp->size();
193      for(G4int j=0; j<np; j++) {
194        G4DynamicParticle* dp = (*newp)[j];
195        G4LorentzVector v = dp->Get4Momentum();
196        v.boost(boost);
197        v.boost(inBoost);
198        dp->Set4Momentum(v);
199      }
200      gLv.boost(inBoost);
201      gamma->Set4Momentum(gLv);
202      newp->push_back(gamma);
203    }
204  }
205}
206
207//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
208
209void G4eeToHadronsModel::ComputeCMCrossSectionPerElectron()
210{
211  G4bool b;
212  for(G4int i=0; i<nbins; i++) {
213    G4double e  = crossPerElectron->GetLowEdgeEnergy(i);
214    G4double cs = 0.0;
215    if(i > 0) {
216      G4double L   = 2.0*log(e/electron_mass_c2);
217      G4double bt  = 2.0*fine_structure_const*(L - 1.0)/pi;
218      G4double btm1= bt - 1.0;
219      G4double del = 1. + fine_structure_const*(1.5*L + pi*pi/3. -2.)/pi;
220      G4double s1  = crossBornPerElectron->GetValue(e, b);
221      G4double e1  = crossPerElectron->GetLowEdgeEnergy(i-1);
222      G4double x1  = 1. - e1/e;
223      cs += s1*(del*pow(x1,bt) - bt*(x1 - 0.25*x1*x1));
224      if(i > 1) {
225        G4double e2  = e1;
226        G4double x2  = x1;
227        G4double s2  = crossBornPerElectron->GetValue(e2, b);
228        G4double w2  = bt*(del*pow(x2,btm1) - 1.0 + 0.5*x2);
229     
230        for(G4int j=i-2; j>=0; j--) {
231          e1  = crossPerElectron->GetLowEdgeEnergy(j);
232          x1  = 1. - e1/e;
233          G4double s1 = crossBornPerElectron->GetValue(e1, b);
234          G4double w1 = bt*(del*pow(x1,btm1) - 1.0 + 0.5*x1);
235          cs += 0.5*(x1 - x2)*(w2*s2 + w1*s1);
236          e2 = e1;
237          x2 = x1;
238          s2 = s1;
239          w2 = w1;
240        }
241      }
242    }
243    crossPerElectron->PutValue(i, cs);
244    //    G4cout << "e= " << e << "  cs= " << cs << G4endl;
245  }
246}
247
248//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
249
250G4DynamicParticle* G4eeToHadronsModel::GenerateCMPhoton(G4double e)
251{
252  G4bool b;   
253  G4double x;
254  G4DynamicParticle* gamma = 0;
255  G4double L   = 2.0*log(e/electron_mass_c2);
256  G4double bt  = 2.0*fine_structure_const*(L - 1.)/pi;
257  G4double btm1= bt - 1.0;
258  G4double del = 1. + fine_structure_const*(1.5*L + pi*pi/3. -2.)/pi;
259
260  G4double s0 = crossBornPerElectron->GetValue(e, b);
261  G4double de = (emax - emin)/(G4double)nbins;
262  G4double x0 = min(de,e - emin)/e;
263  G4double ds = crossBornPerElectron->GetValue(e, b)
264              *(del*pow(x0,bt) - bt*(x0 - 0.25*x0*x0));
265  G4double e1 = e*(1. - x0);
266
267  if(e1 < emax && s0*G4UniformRand()<ds) { 
268    x = x0*pow(G4UniformRand(),1./bt);
269  } else {   
270
271    x  = 1. - e1/e;
272    G4double s1 = crossBornPerElectron->GetValue(e1, b);
273    G4double w1 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
274    G4double grej = s1*w1;
275    G4double f;
276    //    G4cout << "e= " << e/GeV << " epeak= " << epeak/GeV
277    //       << " s1= " << s1 << " w1= " << w1
278    //       << " grej= " << grej << G4endl;
279    // Above emax cross section is 0
280    if(e1 > emax) {
281      x  = 1. - emax/e;
282      G4double s2 = crossBornPerElectron->GetValue(emax, b);
283      G4double w2 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
284      grej = s2*w2;
285      //  G4cout << "emax= " << emax << " s2= " << s2 << " w2= " << w2
286      //   << " grej= " << grej << G4endl;
287    }
288
289    if(e1 > epeak) {
290      x  = 1. - epeak/e;
291      G4double s2 = crossBornPerElectron->GetValue(epeak, b);
292      G4double w2 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
293      grej = max(grej,s2*w2);
294      //G4cout << "epeak= " << epeak << " s2= " << s2 << " w2= " << w2
295      //     << " grej= " << grej << G4endl;
296    }
297    G4double xmin = 1. - e1/e;
298    if(e1 > emax) xmin = 1. - emax/e;
299    G4double xmax = 1. - emin/e;
300    do {
301      x = xmin + G4UniformRand()*(xmax - xmin);
302      G4double s2 = crossBornPerElectron->GetValue((1.0 - x)*e, b);
303      G4double w2 = bt*(del*pow(x,btm1) - 1.0 + 0.5*x);
304      //G4cout << "x= " << x << " xmin= " << xmin << " xmax= " << xmax
305      //     << " s2= " << s2 << " w2= " << w2
306      //           << G4endl;
307      f = s2*w2;
308      if(f > grej) {
309        G4cout << "G4DynamicParticle* G4eeToHadronsModel:WARNING "
310               << f << " > " << grej << " majorant is`small!" 
311               << G4endl; 
312      }
313    } while (f < grej*G4UniformRand());
314  }
315
316  G4ThreeVector dir(0.0,0.0,1.0);
317  gamma = new G4DynamicParticle(theGamma,dir,x*e);
318  return gamma;
319}
320
321//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
322
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