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G4PolarizedMollerBhabhaModel.cc
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25 //
26 // -------------------------------------------------------------------
27 //
28 // GEANT4 Class file
29 //
30 // File name: G4PolarizedMollerBhabhaModel
31 //
32 // Author: A.Schaelicke on base of Vladimir Ivanchenko code
33 //
34 // Creation date: 10.11.2005
35 //
36 // Modifications:
37 //
38 // 20-08-05, modified interface (A.Schaelicke)
39 //
40 // Class Description:
41 //
42 // Implementation of energy loss and delta-electron production by e+/e-
43 // (including polarization effects)
44 //
45 // -------------------------------------------------------------------
46 //
47 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
48 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
49 
50 #include "G4PolarizedMollerBhabhaModel.hh"
51 #include "G4PhysicalConstants.hh"
52 #include "G4Electron.hh"
53 #include "G4Positron.hh"
54 #include "G4ParticleChangeForLoss.hh"
55 #include "Randomize.hh"
56 
57 #include "G4PolarizationManager.hh"
58 #include "G4PolarizationHelper.hh"
59 #include "G4PolarizedBhabhaCrossSection.hh"
60 #include "G4PolarizedMollerCrossSection.hh"
61 
62 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
63 
64 G4PolarizedMollerBhabhaModel::G4PolarizedMollerBhabhaModel(const G4ParticleDefinition* p,
65  const G4String& nam)
66  : G4MollerBhabhaModel(p,nam)
67 {
68 
69  // G4cout<<" particle==electron "<<(p==theElectron)<<G4endl;
70  isElectron=(p==theElectron); // necessary due to wrong order in G4MollerBhabhaModel constructor!
71 
72  if (p==nullptr) {
73 
74  }
75  if (!isElectron) {
76  G4cout<<" buildBhabha cross section "<<isElectron<<G4endl;
77  crossSectionCalculator = new G4PolarizedBhabhaCrossSection();
78  } else {
79  G4cout<<" buildMoller cross section "<<isElectron<<G4endl;
80  crossSectionCalculator = new G4PolarizedMollerCrossSection();
81  }
82 }
83 
84 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
85 
86 G4PolarizedMollerBhabhaModel::~G4PolarizedMollerBhabhaModel()
87 {
88  if (crossSectionCalculator) {
89  delete crossSectionCalculator;
90  }
91 }
92 
93 
94 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
95 
96 G4double G4PolarizedMollerBhabhaModel::ComputeCrossSectionPerElectron(
97  const G4ParticleDefinition* pd,
98  G4double kinEnergy,
99  G4double cut,
100  G4double emax)
101 {
102  G4double xs =
103  G4MollerBhabhaModel::ComputeCrossSectionPerElectron(pd,kinEnergy,
104  cut,emax);
105 // G4cout<<"calc eIoni xsec "<<xs<<G4endl;
106 // G4cout<<" "<<kinEnergy<<" "<<cut<<" "<<emax<<G4endl;
107  G4double factor=1.;
108  if (xs!=0.) {
109  // G4cout<<"calc asym"<<G4endl;
110  G4double tmax = MaxSecondaryEnergy(pd, kinEnergy);
111  tmax = std::min(emax, tmax);
112 
113  if (std::fabs(cut/emax-1.)<1.e-10) return xs;
114 
115  if(cut < tmax) {
116 
117  G4double xmin = cut/kinEnergy;
118  G4double xmax = tmax/kinEnergy;
119 // G4cout<<"calc asym "<<xmin<<","<<xmax<<G4endl;
120  G4double gam = kinEnergy/electron_mass_c2 + 1.0;
121 
122  G4double crossPol=crossSectionCalculator->
123  TotalXSection(xmin,xmax,gam,
124  theBeamPolarization,
125  theTargetPolarization);
126  G4double crossUnpol=crossSectionCalculator->
127  TotalXSection(xmin,xmax,gam,
128  G4StokesVector::ZERO,
129  G4StokesVector::ZERO);
130  if (crossUnpol>0.) factor=crossPol/crossUnpol;
131  // G4cout<<" factor="<<factor<<G4endl;
132  }
133  }
134  return xs*factor;
135 }
136 
137 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
138 
139 void G4PolarizedMollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
140  const G4MaterialCutsCouple* ,
141  const G4DynamicParticle* dp,
142  G4double tmin,
143  G4double maxEnergy)
144 {
145  // *** obtain and save target and beam polarization ***
146  G4PolarizationManager * polarizationManger = G4PolarizationManager::GetInstance();
147 
148  const G4Track * aTrack = fParticleChange->GetCurrentTrack();
149 
150  // obtain polarization of the beam
151  theBeamPolarization = dp->GetPolarization();
152 
153  // obtain polarization of the media
154  G4VPhysicalVolume* aPVolume = aTrack->GetVolume();
155  G4LogicalVolume* aLVolume = aPVolume->GetLogicalVolume();
156  const G4bool targetIsPolarized = polarizationManger->IsPolarized(aLVolume);
157  theTargetPolarization = polarizationManger->GetVolumePolarization(aLVolume);
158 
159  // transfer target polarization in interaction frame
160  if (targetIsPolarized)
161  theTargetPolarization.rotateUz(dp->GetMomentumDirection());
162 
163 
164 
165 
166  G4double tmax = std::min(maxEnergy, MaxSecondaryKinEnergy(dp));
167  if(tmin >= tmax) return;
168  // if(tmin > tmax) tmin = tmax;
169 
170  G4double polL = theBeamPolarization.z()*theTargetPolarization.z();
171  polL=std::fabs(polL);
172  G4double polT = theBeamPolarization.x()*theTargetPolarization.x() +
173  theBeamPolarization.y()*theTargetPolarization.y();
174  polT=std::fabs(polT);
175 
176  G4double kineticEnergy = dp->GetKineticEnergy();
177  G4double energy = kineticEnergy + electron_mass_c2;
178  G4double totalMomentum = std::sqrt(kineticEnergy*(energy + electron_mass_c2));
179  G4double xmin = tmin/kineticEnergy;
180  G4double xmax = tmax/kineticEnergy;
181  G4double gam = energy/electron_mass_c2;
182  G4double gamma2 = gam*gam;
183  G4double gmo = gam - 1.;
184  G4double gmo2 = gmo*gmo;
185  G4double gmo3 = gmo2*gmo;
186  G4double gpo = gam + 1.;
187  G4double gpo2 = gpo*gpo;
188  G4double gpo3 = gpo2*gpo;
189  G4double x, y, q, grej, grej2;
190  G4double z = 0.;
191  G4double xs = 0., phi =0.;
192  G4ThreeVector direction = dp->GetMomentumDirection();
193 
194  //(Polarized) Moller (e-e-) scattering
195  if (isElectron) {
196  // *** dice according to polarized cross section
197  G4double G = ((2.0*gam - 1.0)/gamma2)*(1. - polT - polL*gam);
198  G4double H = (sqr(gam - 1.0)/gamma2)*(1. + polT + polL*((gam + 3.)/(gam - 1.)));
199 
200  y = 1.0 - xmax;
201  grej = 1.0 - G*xmax + xmax*xmax*(H + (1.0 - G*y)/(y*y));
202  grej2 = 1.0 - G*xmin + xmin*xmin*(H + (1.0 - G*y)/(y*y));
203  if (grej2 > grej) grej = grej2;
204  G4double prefM = gamma2*classic_electr_radius*classic_electr_radius/(gmo2*(gam + 1.0));
205  grej *= prefM;
206  do {
207  q = G4UniformRand();
208  x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
209  if (crossSectionCalculator) {
210  crossSectionCalculator->Initialize(x,gam,phi,theBeamPolarization,
211  theTargetPolarization,1);
212  xs=crossSectionCalculator->XSection(G4StokesVector::ZERO,
213  G4StokesVector::ZERO);
214  z=xs*sqr(x)*4.;
215  if (grej < z) {
216  G4cout<<"WARNING : error in Moller rejection routine! \n"
217  <<" z = "<<z<<" grej="<<grej<<"\n";
218  }
219  } else {
220  G4cout<<"No calculator in Moller scattering"<<G4endl;
221  }
222  // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
223  } while(grej * G4UniformRand() > z);
224  //Bhabha (e+e-) scattering
225  } else {
226  // *** dice according to polarized cross section
227  y = xmax*xmax;
228  grej = 0.;
229  grej += y*y*gmo3*(1. + (polL + polT)*(gam + 3.)/gmo);
230  grej += -2.*xmin*xmin*xmin*gam*gmo2*(1. - (polL + polT)*(gam + 3.)/gmo);
231  grej += y*y*gmo*(3.*gamma2 + 6.*gam + 4.)*(1. + (polL*(3.*gam + 1.)*(gamma2 + gam + 1.) + polT*((gam + 2.)*gamma2 + 1.))/(gmo*(3.*gam*(gam + 2.) + 4.)));
232  grej /= gpo3;
233  grej += -xmin*(2.*gamma2 + 4.*gam + 1.)*(1. - gam*(polL*(2.*gam + 1.) + polT)/(2.*gam*(gam + 2.) + 1.))/gpo2;
234  grej += gamma2/(gamma2 - 1.);
235  G4double prefB = classic_electr_radius*classic_electr_radius/(gam - 1.0);
236  grej *= prefB;
237 
238  do {
239  q = G4UniformRand();
240  x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
241  if (crossSectionCalculator) {
242  crossSectionCalculator->Initialize(x,gam,phi,theBeamPolarization,
243  theTargetPolarization,1);
244  xs=crossSectionCalculator->XSection(G4StokesVector::ZERO,
245  G4StokesVector::ZERO);
246  z=xs*sqr(x)*4.;
247  } else {
248  G4cout<<"No calculator in Bhabha scattering"<<G4endl;
249  }
250 
251  if(z > grej) {
252  G4cout<<"&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&"<<G4endl;
253  G4cout << "G4PolarizedMollerBhabhaModel::SampleSecondaries Warning! "<<G4endl
254  << "Majorant " << grej << " < "
255  << z << " for x= " << x<<G4endl
256  << " e+e- (Bhabha) scattering"<<" at KinEnergy "<<kineticEnergy<<G4endl;
257  G4cout<<"&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&"<<G4endl;
258  }
259  // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
260  } while(grej * G4UniformRand() > z);
261  }
262  //
263  //
264  // polar asymmetries (due to transverse polarizations)
265  //
266  //
267  if (crossSectionCalculator) {
268  // grej*=1./(sqr(x)*sqr(gamma2-1))*sqr(gam*(1+gam));
269  grej=xs*2.;
270  do {
271  phi = twopi * G4UniformRand() ;
272  crossSectionCalculator->Initialize(x,gam,phi,theBeamPolarization,
273  theTargetPolarization,1);
274  xs=crossSectionCalculator->XSection(G4StokesVector::ZERO,
275  G4StokesVector::ZERO);
276  if(xs > grej) {
277  if (isElectron){
278  G4cout << "G4PolarizedMollerBhabhaModel::SampleSecondaries Warning! "<<G4endl
279  << "Majorant " << grej << " < "
280  << xs << " for phi= " << phi<<G4endl
281  << " e-e- (Moller) scattering"<< G4endl
282  <<"PHI DICING"<<G4endl;
283  } else {
284  G4cout << "G4PolarizedMollerBhabhaModel::SampleSecondaries Warning! "<<G4endl
285  << "Majorant " << grej << " < "
286  << xs << " for phi= " << phi<<G4endl
287  << " e+e- (Bhabha) scattering"<< G4endl
288  <<"PHI DICING"<<G4endl;
289  }
290  }
291  // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
292  } while(grej * G4UniformRand() > xs);
293  }
294 
295  // fix kinematics of delta electron
296  G4double deltaKinEnergy = x * kineticEnergy;
297  G4double deltaMomentum =
298  std::sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
299  G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
300  (deltaMomentum * totalMomentum);
301  G4double sint = 1.0 - cost*cost;
302  if(sint > 0.0) sint = std::sqrt(sint);
303 
304 
305  G4ThreeVector deltaDirection(-sint*std::cos(phi),-sint*std::sin(phi), cost) ;
306  deltaDirection.rotateUz(direction);
307 
308  // primary change
309  kineticEnergy -= deltaKinEnergy;
310  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
311 
312  if(kineticEnergy > DBL_MIN) {
313  G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
314  direction = dir.unit();
315  fParticleChange->SetProposedMomentumDirection(direction);
316  }
317 
318  // create G4DynamicParticle object for delta ray
319  G4DynamicParticle* delta = new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy);
320  vdp->push_back(delta);
321 
322  // get interaction frame
323  G4ThreeVector nInteractionFrame =
324  G4PolarizationHelper::GetFrame(direction,deltaDirection);
325 
326  if (crossSectionCalculator) {
327  // calculate mean final state polarizations
328 
329  theBeamPolarization.InvRotateAz(nInteractionFrame,direction);
330  theTargetPolarization.InvRotateAz(nInteractionFrame,direction);
331  crossSectionCalculator->Initialize(x,gam,phi,theBeamPolarization,
332  theTargetPolarization,2);
333 
334  // electron/positron
335  fPositronPolarization=crossSectionCalculator->GetPol2();
336  fPositronPolarization.RotateAz(nInteractionFrame,direction);
337 
338  fParticleChange->ProposePolarization(fPositronPolarization);
339 
340  // electron
341  fElectronPolarization=crossSectionCalculator->GetPol3();
342  fElectronPolarization.RotateAz(nInteractionFrame,deltaDirection);
343  delta->SetPolarization(fElectronPolarization.x(),
344  fElectronPolarization.y(),
345  fElectronPolarization.z());
346  }
347  else {
348  fPositronPolarization=G4ThreeVector();
349  fElectronPolarization=G4ThreeVector();
350  }
351 }
352 
353 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......