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G4PolarizedMollerBhabhaModel.cc
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26 // $Id: G4PolarizedMollerBhabhaModel.cc 69847 2013-05-16 09:36:18Z gcosmo $
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 // File name: G4PolarizedMollerBhabhaModel
32 //
33 // Author: A.Schaelicke on base of Vladimir Ivanchenko code
34 //
35 // Creation date: 10.11.2005
36 //
37 // Modifications:
38 //
39 // 20-08-05, modified interface (A.Schaelicke)
40 //
41 // Class Description:
42 //
43 // Implementation of energy loss and delta-electron production by e+/e-
44 // (including polarization effects)
45 //
46 // -------------------------------------------------------------------
47 //
48 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
49 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
50 
51 #include "G4PolarizedMollerBhabhaModel.hh"
52 #include "G4PhysicalConstants.hh"
53 #include "G4Electron.hh"
54 #include "G4Positron.hh"
55 #include "G4ParticleChangeForLoss.hh"
56 #include "Randomize.hh"
57 
58 #include "G4PolarizationManager.hh"
59 #include "G4PolarizationHelper.hh"
60 #include "G4PolarizedBhabhaCrossSection.hh"
61 #include "G4PolarizedMollerCrossSection.hh"
62 
63 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
64 
65 G4PolarizedMollerBhabhaModel::G4PolarizedMollerBhabhaModel(const G4ParticleDefinition* p,
66  const G4String& nam)
67  : G4MollerBhabhaModel(p,nam)
68 {
69 
70  // G4cout<<" particle==electron "<<(p==theElectron)<<G4endl;
71  isElectron=(p==theElectron); // necessary due to wrong order in G4MollerBhabhaModel constructor!
72 
73  if (p==0) {
74 
75  }
76  if (!isElectron) {
77  G4cout<<" buildBhabha cross section "<<isElectron<<G4endl;
78  crossSectionCalculator = new G4PolarizedBhabhaCrossSection();
79  } else {
80  G4cout<<" buildMoller cross section "<<isElectron<<G4endl;
81  crossSectionCalculator = new G4PolarizedMollerCrossSection();
82  }
83 }
84 
85 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
86 
87 G4PolarizedMollerBhabhaModel::~G4PolarizedMollerBhabhaModel()
88 {
89  if (crossSectionCalculator) {
90  delete crossSectionCalculator;
91  }
92 }
93 
94 
95 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
96 
97 G4double G4PolarizedMollerBhabhaModel::ComputeCrossSectionPerElectron(
98  const G4ParticleDefinition* pd,
99  G4double kinEnergy,
100  G4double cut,
101  G4double emax)
102 {
103  G4double xs =
104  G4MollerBhabhaModel::ComputeCrossSectionPerElectron(pd,kinEnergy,
105  cut,emax);
106 // G4cout<<"calc eIoni xsec "<<xs<<G4endl;
107 // G4cout<<" "<<kinEnergy<<" "<<cut<<" "<<emax<<G4endl;
108  G4double factor=1.;
109  if (xs!=0) {
110  // G4cout<<"calc asym"<<G4endl;
111  G4double tmax = MaxSecondaryEnergy(pd, kinEnergy);
112  tmax = std::min(emax, tmax);
113 
114  if (std::fabs(cut/emax-1.)<1.e-10) return xs;
115 
116  if(cut < tmax) {
117 
118  G4double xmin = cut/kinEnergy;
119  G4double xmax = tmax/kinEnergy;
120 // G4cout<<"calc asym "<<xmin<<","<<xmax<<G4endl;
121  G4double gam = kinEnergy/electron_mass_c2 + 1.0;
122 
123  G4double crossPol=crossSectionCalculator->
124  TotalXSection(xmin,xmax,gam,
125  theBeamPolarization,
126  theTargetPolarization);
127  G4double crossUnpol=crossSectionCalculator->
128  TotalXSection(xmin,xmax,gam,
129  G4StokesVector::ZERO,
130  G4StokesVector::ZERO);
131  if (crossUnpol>0.) factor=crossPol/crossUnpol;
132  // G4cout<<" factor="<<factor<<G4endl;
133  }
134  }
135  return xs*factor;
136 }
137 
138 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
139 
140 void G4PolarizedMollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
141  const G4MaterialCutsCouple* ,
142  const G4DynamicParticle* dp,
143  G4double tmin,
144  G4double maxEnergy)
145 {
146  // *** obtain and save target and beam polarization ***
147  G4PolarizationManager * polarizationManger = G4PolarizationManager::GetInstance();
148 
149  const G4Track * aTrack = fParticleChange->GetCurrentTrack();
150 
151  // obtain polarization of the beam
152  theBeamPolarization = dp->GetPolarization();
153 
154  // obtain polarization of the media
155  G4VPhysicalVolume* aPVolume = aTrack->GetVolume();
156  G4LogicalVolume* aLVolume = aPVolume->GetLogicalVolume();
157  const G4bool targetIsPolarized = polarizationManger->IsPolarized(aLVolume);
158  theTargetPolarization = polarizationManger->GetVolumePolarization(aLVolume);
159 
160  // transfer target polarization in interaction frame
161  if (targetIsPolarized)
162  theTargetPolarization.rotateUz(dp->GetMomentumDirection());
163 
164 
165 
166 
167  G4double tmax = std::min(maxEnergy, MaxSecondaryKinEnergy(dp));
168  if(tmin >= tmax) return;
169  // if(tmin > tmax) tmin = tmax;
170 
171  G4double polL = theBeamPolarization.z()*theTargetPolarization.z();
172  polL=std::fabs(polL);
173  G4double polT = theBeamPolarization.x()*theTargetPolarization.x() +
174  theBeamPolarization.y()*theTargetPolarization.y();
175  polT=std::fabs(polT);
176 
177  G4double kineticEnergy = dp->GetKineticEnergy();
178  G4double energy = kineticEnergy + electron_mass_c2;
179  G4double totalMomentum = std::sqrt(kineticEnergy*(energy + electron_mass_c2));
180  G4double xmin = tmin/kineticEnergy;
181  G4double xmax = tmax/kineticEnergy;
182  G4double gam = energy/electron_mass_c2;
183  G4double gamma2 = gam*gam;
184  G4double gmo = gam - 1.;
185  G4double gmo2 = gmo*gmo;
186  G4double gmo3 = gmo2*gmo;
187  G4double gpo = gam + 1.;
188  G4double gpo2 = gpo*gpo;
189  G4double gpo3 = gpo2*gpo;
190  G4double x, y, q, grej, grej2;
191  G4double z = 0.;
192  G4double xs = 0., phi =0.;
193  G4ThreeVector direction = dp->GetMomentumDirection();
194 
195  //(Polarized) Moller (e-e-) scattering
196  if (isElectron) {
197  // *** dice according to polarized cross section
198  G4double G = ((2.0*gam - 1.0)/gamma2)*(1. - polT - polL*gam);
199  G4double H = (sqr(gam - 1.0)/gamma2)*(1. + polT + polL*((gam + 3.)/(gam - 1.)));
200 
201  y = 1.0 - xmax;
202  grej = 1.0 - G*xmax + xmax*xmax*(H + (1.0 - G*y)/(y*y));
203  grej2 = 1.0 - G*xmin + xmin*xmin*(H + (1.0 - G*y)/(y*y));
204  if (grej2 > grej) grej = grej2;
205  G4double prefM = gamma2*classic_electr_radius*classic_electr_radius/(gmo2*(gam + 1.0));
206  grej *= prefM;
207  do {
208  q = G4UniformRand();
209  x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
210  if (crossSectionCalculator) {
211  crossSectionCalculator->Initialize(x,gam,phi,theBeamPolarization,
212  theTargetPolarization,1);
213  xs=crossSectionCalculator->XSection(G4StokesVector::ZERO,
214  G4StokesVector::ZERO);
215  z=xs*sqr(x)*4.;
216  if (grej < z) {
217  G4cout<<"WARNING : error in Moller rejection routine! \n"
218  <<" z = "<<z<<" grej="<<grej<<"\n";
219  }
220  } else {
221  G4cout<<"No calculator in Moller scattering"<<G4endl;
222  }
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  } while(grej * G4UniformRand() > z);
260  }
261  //
262  //
263  // polar asymmetries (due to transverse polarizations)
264  //
265  //
266  if (crossSectionCalculator) {
267  // grej*=1./(sqr(x)*sqr(gamma2-1))*sqr(gam*(1+gam));
268  grej=xs*2.;
269  do {
270  phi = twopi * G4UniformRand() ;
271  crossSectionCalculator->Initialize(x,gam,phi,theBeamPolarization,
272  theTargetPolarization,1);
273  xs=crossSectionCalculator->XSection(G4StokesVector::ZERO,
274  G4StokesVector::ZERO);
275  if(xs > grej) {
276  if (isElectron){
277  G4cout << "G4PolarizedMollerBhabhaModel::SampleSecondaries Warning! "<<G4endl
278  << "Majorant " << grej << " < "
279  << xs << " for phi= " << phi<<G4endl
280  << " e-e- (Moller) scattering"<< G4endl
281  <<"PHI DICING"<<G4endl;
282  } else {
283  G4cout << "G4PolarizedMollerBhabhaModel::SampleSecondaries Warning! "<<G4endl
284  << "Majorant " << grej << " < "
285  << xs << " for phi= " << phi<<G4endl
286  << " e+e- (Bhabha) scattering"<< G4endl
287  <<"PHI DICING"<<G4endl;
288  }
289  }
290  } while(grej * G4UniformRand() > xs);
291  }
292 
293  // fix kinematics of delta electron
294  G4double deltaKinEnergy = x * kineticEnergy;
295  G4double deltaMomentum =
296  std::sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
297  G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
298  (deltaMomentum * totalMomentum);
299  G4double sint = 1.0 - cost*cost;
300  if(sint > 0.0) sint = std::sqrt(sint);
301 
302 
303  G4ThreeVector deltaDirection(-sint*std::cos(phi),-sint*std::sin(phi), cost) ;
304  deltaDirection.rotateUz(direction);
305 
306  // primary change
307  kineticEnergy -= deltaKinEnergy;
308  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
309 
310  if(kineticEnergy > DBL_MIN) {
311  G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
312  direction = dir.unit();
313  fParticleChange->SetProposedMomentumDirection(direction);
314  }
315 
316  // create G4DynamicParticle object for delta ray
317  G4DynamicParticle* delta = new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy);
318  vdp->push_back(delta);
319 
320  // get interaction frame
321  G4ThreeVector nInteractionFrame =
322  G4PolarizationHelper::GetFrame(direction,deltaDirection);
323 
324  if (crossSectionCalculator) {
325  // calculate mean final state polarizations
326 
327  theBeamPolarization.InvRotateAz(nInteractionFrame,direction);
328  theTargetPolarization.InvRotateAz(nInteractionFrame,direction);
329  crossSectionCalculator->Initialize(x,gam,phi,theBeamPolarization,
330  theTargetPolarization,2);
331 
332  // electron/positron
333  fPositronPolarization=crossSectionCalculator->GetPol2();
334  fPositronPolarization.RotateAz(nInteractionFrame,direction);
335 
336  fParticleChange->ProposePolarization(fPositronPolarization);
337 
338  // electron
339  fElectronPolarization=crossSectionCalculator->GetPol3();
340  fElectronPolarization.RotateAz(nInteractionFrame,deltaDirection);
341  delta->SetPolarization(fElectronPolarization.x(),
342  fElectronPolarization.y(),
343  fElectronPolarization.z());
344  }
345  else {
346  fPositronPolarization=G4ThreeVector();
347  fElectronPolarization=G4ThreeVector();
348  }
349 }
350 
351 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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