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27 //
28 // Geant4 Class file
29 //
30 // File name: G4PolarizedAnnihilationModel
31 //
32 // Author: Andreas Schaelicke
33 //
34 // Class Description:
35 // Implementation of polarized gamma Annihilation scattering on free electron
36
37 #include "G4PolarizedAnnihilationModel.hh"
38
39 #include "G4Gamma.hh"
40 #include "G4ParticleChangeForGamma.hh"
41 #include "G4PhysicalConstants.hh"
42 #include "G4PolarizationHelper.hh"
43 #include "G4PolarizationManager.hh"
44 #include "G4PolarizedAnnihilationXS.hh"
45 #include "G4StokesVector.hh"
46 #include "G4TrackStatus.hh"
47
48 G4PolarizedAnnihilationModel::G4PolarizedAnnihilationModel(
49 const G4ParticleDefinition* p, const G4String& nam)
50 : G4eeToTwoGammaModel(p, nam)
51 , fCrossSectionCalculator(nullptr)
52 , fParticleChange(nullptr)
53 , fVerboseLevel(0)
54 {
55 fCrossSectionCalculator = new G4PolarizedAnnihilationXS();
56 fBeamPolarization = G4StokesVector::ZERO;
57 fTargetPolarization = G4StokesVector::ZERO;
58 fFinalGamma1Polarization = G4StokesVector::ZERO;
59 fFinalGamma2Polarization = G4StokesVector::ZERO;
60 }
61
62 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
63 G4PolarizedAnnihilationModel::~G4PolarizedAnnihilationModel()
64 {
65 delete fCrossSectionCalculator;
66 }
67
68 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
69 void G4PolarizedAnnihilationModel::Initialise(const G4ParticleDefinition* part,
70 const G4DataVector& dv)
71 {
72 G4eeToTwoGammaModel::Initialise(part, dv);
73 if(fParticleChange)
74 {
75 return;
76 }
77 fParticleChange = GetParticleChangeForGamma();
78 }
79
80 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
81 G4double G4PolarizedAnnihilationModel::ComputeCrossSectionPerElectron(
82 G4double kinEnergy)
83 {
84 // cross section from base model
85 G4double xs = G4eeToTwoGammaModel::ComputeCrossSectionPerElectron(kinEnergy);
86
87 G4double polzz = fBeamPolarization.z() * fTargetPolarization.z();
88 G4double poltt = fBeamPolarization.x() * fTargetPolarization.x() +
89 fBeamPolarization.y() * fTargetPolarization.y();
90 if(polzz != 0 || poltt != 0)
91 {
92 G4double xval, lasym, tasym;
93 ComputeAsymmetriesPerElectron(kinEnergy, xval, lasym, tasym);
94 xs *= (1. + polzz * lasym + poltt * tasym);
95 }
96
97 return xs;
98 }
99
100 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
101 void G4PolarizedAnnihilationModel::ComputeAsymmetriesPerElectron(
102 G4double ene, G4double& valueX, G4double& valueA, G4double& valueT)
103 {
104 // *** calculate asymmetries
105 G4double gam = 1. + ene / electron_mass_c2;
106 G4double xs0 = fCrossSectionCalculator->TotalXSection(
107 0., 1., gam, G4StokesVector::ZERO, G4StokesVector::ZERO);
108 G4double xsA = fCrossSectionCalculator->TotalXSection(
109 0., 1., gam, G4StokesVector::P3, G4StokesVector::P3);
110 G4double xsT1 = fCrossSectionCalculator->TotalXSection(
111 0., 1., gam, G4StokesVector::P1, G4StokesVector::P1);
112 G4double xsT2 = fCrossSectionCalculator->TotalXSection(
113 0., 1., gam, G4StokesVector::P2, G4StokesVector::P2);
114 G4double xsT = 0.5 * (xsT1 + xsT2);
115
116 valueX = xs0;
117 valueA = xsA / xs0 - 1.;
118 valueT = xsT / xs0 - 1.;
119
120 if((valueA < -1) || (1 < valueA))
121 {
122 G4ExceptionDescription ed;
123 ed << " ERROR PolarizedAnnihilationPS::ComputeAsymmetries \n";
124 ed << " something wrong in total cross section calculation (valueA)\n";
125 ed << " LONG: " << valueX << "\t" << valueA << "\t" << valueT
126 << " energy = " << gam << G4endl;
127 G4Exception("G4PolarizedAnnihilationModel::ComputeAsymmetriesPerElectron",
128 "pol004", JustWarning, ed);
129 }
130 if((valueT < -1) || (1 < valueT))
131 {
132 G4ExceptionDescription ed;
133 ed << " ERROR PolarizedAnnihilationPS::ComputeAsymmetries \n";
134 ed << " something wrong in total cross section calculation (valueT)\n";
135 ed << " TRAN: " << valueX << "\t" << valueA << "\t" << valueT
136 << " energy = " << gam << G4endl;
137 G4Exception("G4PolarizedAnnihilationModel::ComputeAsymmetriesPerElectron",
138 "pol005", JustWarning, ed);
139 }
140 }
141
142 void G4PolarizedAnnihilationModel::SampleSecondaries(
143 std::vector<G4DynamicParticle*>* fvect, const G4MaterialCutsCouple*,
144 const G4DynamicParticle* dp, G4double, G4double)
145 {
146 const G4Track* aTrack = fParticleChange->GetCurrentTrack();
147
148 // kill primary
149 fParticleChange->SetProposedKineticEnergy(0.);
150 fParticleChange->ProposeTrackStatus(fStopAndKill);
151
152 // V.Ivanchenko add protection against zero kin energy
153 G4double PositKinEnergy = dp->GetKineticEnergy();
154
155 if(PositKinEnergy == 0.0)
156 {
157 G4double cosTeta = 2. * G4UniformRand() - 1.;
158 G4double sinTeta = std::sqrt((1.0 - cosTeta) * (1.0 + cosTeta));
159 G4double phi = twopi * G4UniformRand();
160 G4ThreeVector dir(sinTeta * std::cos(phi), sinTeta * std::sin(phi),
161 cosTeta);
162 fvect->push_back(
163 new G4DynamicParticle(G4Gamma::Gamma(), dir, electron_mass_c2));
164 fvect->push_back(
165 new G4DynamicParticle(G4Gamma::Gamma(), -dir, electron_mass_c2));
166 return;
167 }
168
169 // *** obtain and save target and beam polarization ***
170 G4PolarizationManager* polarizationManager =
171 G4PolarizationManager::GetInstance();
172
173 // obtain polarization of the beam
174 fBeamPolarization = G4StokesVector(aTrack->GetPolarization());
175
176 // obtain polarization of the media
177 G4VPhysicalVolume* aPVolume = aTrack->GetVolume();
178 G4LogicalVolume* aLVolume = aPVolume->GetLogicalVolume();
179 const G4bool targetIsPolarized = polarizationManager->IsPolarized(aLVolume);
180 fTargetPolarization = polarizationManager->GetVolumePolarization(aLVolume);
181
182 if(fVerboseLevel >= 1)
183 {
184 G4cout << "G4PolarizedComptonModel::SampleSecondaries in "
185 << aLVolume->GetName() << G4endl;
186 }
187
188 // transfer target electron polarization in frame of positron
189 if(targetIsPolarized)
190 fTargetPolarization.rotateUz(dp->GetMomentumDirection());
191
192 G4ParticleMomentum PositDirection = dp->GetMomentumDirection();
193
194 // polar asymmetry:
195 G4double polarization = fBeamPolarization.p3() * fTargetPolarization.p3();
196
197 G4double gamam1 = PositKinEnergy / electron_mass_c2;
198 G4double gama = gamam1 + 1., gamap1 = gamam1 + 2.;
199 G4double sqgrate = std::sqrt(gamam1 / gamap1) / 2.,
200 sqg2m1 = std::sqrt(gamam1 * gamap1);
201
202 // limits of the energy sampling
203 G4double epsilmin = 0.5 - sqgrate, epsilmax = 0.5 + sqgrate;
204 G4double epsilqot = epsilmax / epsilmin;
205
206 // sample the energy rate of the created gammas
207 // note: for polarized partices, the actual dicing strategy
208 // will depend on the energy, and the degree of polarization !!
209 G4double epsil;
210 G4double gmax = 1. + std::fabs(polarization); // crude estimate
211
212 fCrossSectionCalculator->Initialize(epsilmin, gama, 0., fBeamPolarization,
213 fTargetPolarization);
214 if(fCrossSectionCalculator->DiceEpsilon() < 0.)
215 {
216 G4ExceptionDescription ed;
217 ed << "ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
218 << "epsilmin DiceRoutine not appropriate ! "
219 << fCrossSectionCalculator->DiceEpsilon() << G4endl;
220 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol006",
221 JustWarning, ed);
222 }
223
224 fCrossSectionCalculator->Initialize(epsilmax, gama, 0., fBeamPolarization,
225 fTargetPolarization);
226 if(fCrossSectionCalculator->DiceEpsilon() < 0)
227 {
228 G4ExceptionDescription ed;
229 ed << "ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
230 << "epsilmax DiceRoutine not appropriate ! "
231 << fCrossSectionCalculator->DiceEpsilon() << G4endl;
232 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol007",
233 JustWarning, ed);
234 }
235
236 G4int ncount = 0;
237 G4double trejectmax = 0.;
238 G4double treject;
239
240 do
241 {
242 epsil = epsilmin * std::pow(epsilqot, G4UniformRand());
243
244 fCrossSectionCalculator->Initialize(epsil, gama, 0., fBeamPolarization,
245 fTargetPolarization, 1);
246
247 treject = fCrossSectionCalculator->DiceEpsilon();
248 treject *= epsil;
249
250 if(treject > gmax || treject < 0.)
251 {
252 G4ExceptionDescription ed;
253 ed << "ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
254 << " eps (" << epsil
255 << ") rejection does not work properly: " << treject << G4endl;
256 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol008",
257 JustWarning, ed);
258 }
259 ++ncount;
260 if(treject > trejectmax)
261 trejectmax = treject;
262 if(ncount > 1000)
263 {
264 G4ExceptionDescription ed;
265 ed << "WARNING in PolarizedAnnihilationPS::PostStepDoIt\n"
266 << "eps dicing very inefficient =" << trejectmax / gmax << ", "
267 << treject / gmax << ". For secondary energy = " << epsil << " "
268 << ncount << G4endl;
269 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol009",
270 JustWarning, ed);
271 break;
272 }
273
274 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
275 } while(treject < gmax * G4UniformRand());
276
277 // scattered Gamma angles. ( Z - axis along the parent positron)
278 G4double cost = (epsil * gamap1 - 1.) / (epsil * sqg2m1);
279 G4double sint = std::sqrt((1. + cost) * (1. - cost));
280 G4double phi = 0.;
281 G4double beamTrans =
282 std::sqrt(sqr(fBeamPolarization.p1()) + sqr(fBeamPolarization.p2()));
283 G4double targetTrans =
284 std::sqrt(sqr(fTargetPolarization.p1()) + sqr(fTargetPolarization.p2()));
285
286 do
287 {
288 phi = twopi * G4UniformRand();
289 fCrossSectionCalculator->Initialize(epsil, gama, 0., fBeamPolarization,
290 fTargetPolarization, 2);
291
292 G4double gdiced = fCrossSectionCalculator->getVar(0);
293 gdiced += fCrossSectionCalculator->getVar(3) * fBeamPolarization.p3() *
294 fTargetPolarization.p3();
295 gdiced += 1. *
296 (std::fabs(fCrossSectionCalculator->getVar(1)) +
297 std::fabs(fCrossSectionCalculator->getVar(2))) *
298 beamTrans * targetTrans;
299 gdiced += 1. * std::fabs(fCrossSectionCalculator->getVar(4)) *
300 (std::fabs(fBeamPolarization.p3()) * targetTrans +
301 std::fabs(fTargetPolarization.p3()) * beamTrans);
302
303 G4double gdist = fCrossSectionCalculator->getVar(0);
304 gdist += fCrossSectionCalculator->getVar(3) * fBeamPolarization.p3() *
305 fTargetPolarization.p3();
306 gdist += fCrossSectionCalculator->getVar(1) *
307 (std::cos(phi) * fBeamPolarization.p1() +
308 std::sin(phi) * fBeamPolarization.p2()) *
309 (std::cos(phi) * fTargetPolarization.p1() +
310 std::sin(phi) * fTargetPolarization.p2());
311 gdist += fCrossSectionCalculator->getVar(2) *
312 (std::cos(phi) * fBeamPolarization.p2() -
313 std::sin(phi) * fBeamPolarization.p1()) *
314 (std::cos(phi) * fTargetPolarization.p2() -
315 std::sin(phi) * fTargetPolarization.p1());
316 gdist +=
317 fCrossSectionCalculator->getVar(4) *
318 (std::cos(phi) * fBeamPolarization.p3() * fTargetPolarization.p1() +
319 std::cos(phi) * fBeamPolarization.p1() * fTargetPolarization.p3() +
320 std::sin(phi) * fBeamPolarization.p3() * fTargetPolarization.p2() +
321 std::sin(phi) * fBeamPolarization.p2() * fTargetPolarization.p3());
322
323 treject = gdist / gdiced;
324 if(treject > 1. + 1.e-10 || treject < 0)
325 {
326 G4ExceptionDescription ed;
327 ed << "!!!ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
328 << " phi rejection does not work properly: " << treject << G4endl;
329 G4cout << " gdiced = " << gdiced << G4endl;
330 G4cout << " gdist = " << gdist << G4endl;
331 G4cout << " epsil = " << epsil << G4endl;
332 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol009",
333 JustWarning, ed);
334 }
335
336 if(treject < 1.e-3)
337 {
338 G4ExceptionDescription ed;
339 ed << "!!!ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
340 << " phi rejection does not work properly: " << treject << "\n";
341 G4cout << " gdiced=" << gdiced << " gdist=" << gdist << "\n";
342 G4cout << " epsil = " << epsil << G4endl;
343 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol010",
344 JustWarning, ed);
345 }
346
347 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
348 } while(treject < G4UniformRand());
349
350 G4double dirx = sint * std::cos(phi);
351 G4double diry = sint * std::sin(phi);
352 G4double dirz = cost;
353
354 // kinematic of the created pair
355 G4double TotalAvailableEnergy = PositKinEnergy + 2 * electron_mass_c2;
356 G4double Phot1Energy = epsil * TotalAvailableEnergy;
357 G4double Phot2Energy = (1. - epsil) * TotalAvailableEnergy;
358
359 // *** prepare calculation of polarization transfer ***
360 G4ThreeVector Phot1Direction(dirx, diry, dirz);
361
362 // get interaction frame
363 G4ThreeVector nInteractionFrame =
364 G4PolarizationHelper::GetFrame(PositDirection, Phot1Direction);
365
366 // define proper in-plane and out-of-plane component of initial spins
367 fBeamPolarization.InvRotateAz(nInteractionFrame, PositDirection);
368 fTargetPolarization.InvRotateAz(nInteractionFrame, PositDirection);
369
370 // calculate spin transfere matrix
371
372 fCrossSectionCalculator->Initialize(epsil, gama, phi, fBeamPolarization,
373 fTargetPolarization, 2);
374
375 Phot1Direction.rotateUz(PositDirection);
376 // create G4DynamicParticle object for the particle1
377 G4DynamicParticle* aParticle1 =
378 new G4DynamicParticle(G4Gamma::Gamma(), Phot1Direction, Phot1Energy);
379 fFinalGamma1Polarization = fCrossSectionCalculator->GetPol2();
380 G4double n1 = fFinalGamma1Polarization.mag2();
381 if(n1 > 1.)
382 {
383 G4ExceptionDescription ed;
384 ed << "ERROR: PolarizedAnnihilation Polarization Vector at epsil = "
385 << epsil << " is too large!!! \n"
386 << "annihi pol1= " << fFinalGamma1Polarization << ", (" << n1 << ")\n";
387 fFinalGamma1Polarization *= 1. / std::sqrt(n1);
388 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol011",
389 JustWarning, ed);
390 }
391
392 // define polarization of first final state photon
393 fFinalGamma1Polarization.SetPhoton();
394 fFinalGamma1Polarization.RotateAz(nInteractionFrame, Phot1Direction);
395 aParticle1->SetPolarization(fFinalGamma1Polarization.p1(),
396 fFinalGamma1Polarization.p2(),
397 fFinalGamma1Polarization.p3());
398
399 fvect->push_back(aParticle1);
400
401 // **********************************************************************
402
403 G4double Eratio = Phot1Energy / Phot2Energy;
404 G4double PositP =
405 std::sqrt(PositKinEnergy * (PositKinEnergy + 2. * electron_mass_c2));
406 G4ThreeVector Phot2Direction(-dirx * Eratio, -diry * Eratio,
407 (PositP - dirz * Phot1Energy) / Phot2Energy);
408 Phot2Direction.rotateUz(PositDirection);
409 // create G4DynamicParticle object for the particle2
410 G4DynamicParticle* aParticle2 =
411 new G4DynamicParticle(G4Gamma::Gamma(), Phot2Direction, Phot2Energy);
412
413 // define polarization of second final state photon
414 fFinalGamma2Polarization = fCrossSectionCalculator->GetPol3();
415 G4double n2 = fFinalGamma2Polarization.mag2();
416 if(n2 > 1.)
417 {
418 G4ExceptionDescription ed;
419 ed << "ERROR: PolarizedAnnihilation Polarization Vector at epsil = "
420 << epsil << " is too large!!! \n";
421 ed << "annihi pol2= " << fFinalGamma2Polarization << ", (" << n2 << ")\n";
422
423 G4Exception("G4PolarizedAnnihilationModel::SampleSecondaries", "pol012",
424 JustWarning, ed);
425 fFinalGamma2Polarization *= 1. / std::sqrt(n2);
426 }
427 fFinalGamma2Polarization.SetPhoton();
428 fFinalGamma2Polarization.RotateAz(nInteractionFrame, Phot2Direction);
429 aParticle2->SetPolarization(fFinalGamma2Polarization.p1(),
430 fFinalGamma2Polarization.p2(),
431 fFinalGamma2Polarization.p3());
432
433 fvect->push_back(aParticle2);
434 }
435