source: trunk/source/processes/electromagnetic/polarisation/src/G4PolarizedAnnihilationModel.cc@ 819

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25//
26// $Id: G4PolarizedAnnihilationModel.cc,v 1.6 2007/07/10 09:38:17 schaelic Exp $
27// GEANT4 tag $Name: $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4PolarizedAnnihilationModel
35//
36// Author: Andreas Schaelicke
37//
38// Creation date: 01.05.2005
39//
40// Modifications:
41// 18-07-06 use newly calculated cross sections (P. Starovoitov)
42// 21-08-06 update interface (A. Schaelicke)
43// 17-11-06 add protection agaist e+ zero energy PostStep (V.Ivanchenko)
44// 10-07-07 copied Initialise() method from G4eeToTwoGammaModel to provide a
45// local ParticleChangeForGamma object and reduce overhead
46// in SampleSecondaries() (A. Schaelicke)
47//
48//
49// Class Description:
50//
51// Implementation of polarized gamma Annihilation scattering on free electron
52//
53
54// -------------------------------------------------------------------
55#include "G4PolarizedAnnihilationModel.hh"
56#include "G4PolarizationManager.hh"
57#include "G4PolarizationHelper.hh"
58#include "G4StokesVector.hh"
59#include "G4PolarizedAnnihilationCrossSection.hh"
60#include "G4ParticleChangeForGamma.hh"
61#include "G4TrackStatus.hh"
62#include "G4Gamma.hh"
63
64G4PolarizedAnnihilationModel::G4PolarizedAnnihilationModel(const G4ParticleDefinition* p,
65 const G4String& nam)
66 : G4eeToTwoGammaModel(p,nam),crossSectionCalculator(0),gParticleChange(0),
67 gIsInitialised(false)
68{
69 crossSectionCalculator=new G4PolarizedAnnihilationCrossSection();
70}
71
72G4PolarizedAnnihilationModel::~G4PolarizedAnnihilationModel()
73{
74 if (crossSectionCalculator) delete crossSectionCalculator;
75}
76
77
78//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
79
80void G4PolarizedAnnihilationModel::Initialise(const G4ParticleDefinition*,
81 const G4DataVector&)
82{
83 // G4eeToTwoGammaModel::Initialise(part,dv);
84 if(gIsInitialised) return;
85
86 if(pParticleChange)
87 gParticleChange =
88 reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
89 else
90 gParticleChange = new G4ParticleChangeForGamma();
91
92 gIsInitialised = true;
93}
94
95G4double G4PolarizedAnnihilationModel::ComputeCrossSectionPerElectron(
96 const G4ParticleDefinition* pd,
97 G4double kinEnergy,
98 G4double cut,
99 G4double emax)
100{
101 G4double xs = G4eeToTwoGammaModel::ComputeCrossSectionPerElectron(pd,kinEnergy,
102 cut,emax);
103
104 G4double polzz = theBeamPolarization.z()*theTargetPolarization.z();
105 G4double poltt = theBeamPolarization.x()*theTargetPolarization.x()
106 + theBeamPolarization.y()*theTargetPolarization.y();
107 if (polzz!=0 || poltt!=0) {
108 G4double xval,lasym,tasym;
109 ComputeAsymmetriesPerElectron(kinEnergy,xval,lasym,tasym);
110 xs*=(1.+polzz*lasym+poltt*tasym);
111 }
112
113 return xs;
114}
115
116void G4PolarizedAnnihilationModel::ComputeAsymmetriesPerElectron(G4double ene,
117 G4double & valueX,
118 G4double & valueA,
119 G4double & valueT)
120{
121 // *** calculate asymmetries
122 G4double gam = 1. + ene/electron_mass_c2;
123 G4double xs0=crossSectionCalculator->TotalXSection(0.,1.,gam,
124 G4StokesVector::ZERO,
125 G4StokesVector::ZERO);
126 G4double xsA=crossSectionCalculator->TotalXSection(0.,1.,gam,
127 G4StokesVector::P3,
128 G4StokesVector::P3);
129 G4double xsT1=crossSectionCalculator->TotalXSection(0.,1.,gam,
130 G4StokesVector::P1,
131 G4StokesVector::P1);
132 G4double xsT2=crossSectionCalculator->TotalXSection(0.,1.,gam,
133 G4StokesVector::P2,
134 G4StokesVector::P2);
135 G4double xsT=0.5*(xsT1+xsT2);
136
137 valueX=xs0;
138 valueA=xsA/xs0-1.;
139 valueT=xsT/xs0-1.;
140 // G4cout<<valueX<<"\t"<<valueA<<"\t"<<valueT<<" energy = "<<gam<<G4endl;
141 if ( (valueA < -1) || (1 < valueA)) {
142 G4cout<< " ERROR PolarizedAnnihilationPS::ComputeAsymmetries \n";
143 G4cout<< " something wrong in total cross section calculation (valueA)\n";
144 G4cout<<"*********** LONG "<<valueX<<"\t"<<valueA<<"\t"<<valueT<<" energy = "<<gam<<G4endl;
145 }
146 if ( (valueT < -1) || (1 < valueT)) {
147 G4cout<< " ERROR PolarizedAnnihilationPS::ComputeAsymmetries \n";
148 G4cout<< " something wrong in total cross section calculation (valueT)\n";
149 G4cout<<"****** TRAN "<<valueX<<"\t"<<valueA<<"\t"<<valueT<<" energy = "<<gam<<G4endl;
150 }
151}
152
153
154void G4PolarizedAnnihilationModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
155 const G4MaterialCutsCouple* /*couple*/,
156 const G4DynamicParticle* dp,
157 G4double /*tmin*/,
158 G4double /*maxEnergy*/)
159{
160// G4ParticleChangeForGamma* gParticleChange
161// = dynamic_cast<G4ParticleChangeForGamma*>(pParticleChange);
162 const G4Track * aTrack = gParticleChange->GetCurrentTrack();
163
164 // kill primary
165 gParticleChange->SetProposedKineticEnergy(0.);
166 gParticleChange->ProposeTrackStatus(fStopAndKill);
167
168 // V.Ivanchenko add protection against zero kin energy
169 G4double PositKinEnergy = dp->GetKineticEnergy();
170
171 if(PositKinEnergy < DBL_MIN) {
172
173 G4double cosTeta = 2.*G4UniformRand()-1.;
174 G4double sinTeta = std::sqrt((1.0 - cosTeta)*(1.0 + cosTeta));
175 G4double phi = twopi * G4UniformRand();
176 G4ThreeVector dir(sinTeta*std::cos(phi), sinTeta*std::sin(phi), cosTeta);
177 fvect->push_back( new G4DynamicParticle(G4Gamma::Gamma(), dir, electron_mass_c2));
178 fvect->push_back( new G4DynamicParticle(G4Gamma::Gamma(),-dir, electron_mass_c2));
179 return;
180 }
181
182 // *** obtain and save target and beam polarization ***
183 G4PolarizationManager * polarizationManager = G4PolarizationManager::GetInstance();
184
185 // obtain polarization of the beam
186 theBeamPolarization = aTrack->GetPolarization();
187
188 // obtain polarization of the media
189 G4VPhysicalVolume* aPVolume = aTrack->GetVolume();
190 G4LogicalVolume* aLVolume = aPVolume->GetLogicalVolume();
191 const G4bool targetIsPolarized = polarizationManager->IsPolarized(aLVolume);
192 theTargetPolarization = polarizationManager->GetVolumePolarization(aLVolume);
193
194 // transfer target electron polarization in frame of positron
195 if (targetIsPolarized)
196 theTargetPolarization.rotateUz(dp->GetMomentumDirection());
197
198 G4ParticleMomentum PositDirection = dp->GetMomentumDirection();
199
200 // polar asymmetry:
201 G4double polarization = theBeamPolarization.p3()*theTargetPolarization.p3();
202
203 G4double gamam1 = PositKinEnergy/electron_mass_c2;
204 G4double gama = gamam1+1. , gamap1 = gamam1+2.;
205 G4double sqgrate = std::sqrt(gamam1/gamap1)/2. , sqg2m1 = std::sqrt(gamam1*gamap1);
206
207 // limits of the energy sampling
208 G4double epsilmin = 0.5 - sqgrate , epsilmax = 0.5 + sqgrate;
209 G4double epsilqot = epsilmax/epsilmin;
210
211 //
212 // sample the energy rate of the created gammas
213 // note: for polarized partices, the actual dicing strategy
214 // will depend on the energy, and the degree of polarization !!
215 //
216 G4double epsil;
217 G4double gmax=1. + std::fabs(polarization); // crude estimate
218
219 G4bool check_range=true;
220
221 crossSectionCalculator->Initialize(epsilmin, gama, 0., theBeamPolarization, theTargetPolarization);
222 if (crossSectionCalculator->DiceEpsilon()<0) {
223 G4cout<<"ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
224 <<"epsilmin DiceRoutine not appropriate ! "<<crossSectionCalculator->DiceEpsilon()<<G4endl;
225 check_range=false;
226 }
227
228 crossSectionCalculator->Initialize(epsilmax, gama, 0., theBeamPolarization, theTargetPolarization);
229 if (crossSectionCalculator->DiceEpsilon()<0) {
230 G4cout<<"ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
231 <<"epsilmax DiceRoutine not appropriate ! "<<crossSectionCalculator->DiceEpsilon()<<G4endl;
232 check_range=false;
233 }
234
235 G4int ncount=0;
236 G4double trejectmax=0.;
237 G4double treject;
238
239
240 do {
241 //
242 epsil = epsilmin*std::pow(epsilqot,G4UniformRand());
243
244 crossSectionCalculator->Initialize(epsil, gama, 0., theBeamPolarization, theTargetPolarization,1);
245
246 treject = crossSectionCalculator->DiceEpsilon();
247 treject*=epsil;
248
249 if (treject>gmax || treject<0.)
250 G4cout<<"ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
251 <<" eps ("<<epsil<<") rejection does not work properly: "<<treject<<G4endl;
252 ++ncount;
253 if (treject>trejectmax) trejectmax=treject;
254 if (ncount>1000) {
255 G4cout<<"WARNING in PolarizedAnnihilationPS::PostStepDoIt\n"
256 <<"eps dicing very inefficient ="<<trejectmax/gmax
257 <<", "<<treject/gmax<<". For secondary energy = "<<epsil<<" "<<ncount<<G4endl;
258 break;
259 }
260
261 } while( treject < gmax*G4UniformRand() );
262
263 //
264 // scattered Gamma angles. ( Z - axis along the parent positron)
265 //
266
267 G4double cost = (epsil*gamap1-1.)/(epsil*sqg2m1);
268 G4double sint = std::sqrt((1.+cost)*(1.-cost));
269 G4double phi = 0.;
270 G4double beamTrans = std::sqrt(sqr(theBeamPolarization.p1()) + sqr(theBeamPolarization.p2()));
271 G4double targetTrans = std::sqrt(sqr(theTargetPolarization.p1()) + sqr(theTargetPolarization.p2()));
272
273 // G4cout<<"phi dicing START"<<G4endl;
274 do{
275 phi = twopi * G4UniformRand();
276 crossSectionCalculator->Initialize(epsil, gama, 0., theBeamPolarization, theTargetPolarization,2);
277
278 G4double gdiced =crossSectionCalculator->getVar(0);
279 gdiced += crossSectionCalculator->getVar(3)*theBeamPolarization.p3()*theTargetPolarization.p3();
280 gdiced += 1.*(std::fabs(crossSectionCalculator->getVar(1))
281 + std::fabs(crossSectionCalculator->getVar(2)))*beamTrans*targetTrans;
282 gdiced += 1.*std::fabs(crossSectionCalculator->getVar(4))
283 *(std::fabs(theBeamPolarization.p3())*targetTrans + std::fabs(theTargetPolarization.p3())*beamTrans);
284
285 G4double gdist = crossSectionCalculator->getVar(0);
286 gdist += crossSectionCalculator->getVar(3)*theBeamPolarization.p3()*theTargetPolarization.p3();
287 gdist += crossSectionCalculator->getVar(1)*(std::cos(phi)*theBeamPolarization.p1()
288 + std::sin(phi)*theBeamPolarization.p2())
289 *(std::cos(phi)*theTargetPolarization.p1()
290 + std::sin(phi)*theTargetPolarization.p2());
291 gdist += crossSectionCalculator->getVar(2)*(std::cos(phi)*theBeamPolarization.p2()
292 - std::sin(phi)*theBeamPolarization.p1())
293 *(std::cos(phi)*theTargetPolarization.p2()
294 - std::sin(phi)*theTargetPolarization.p1());
295 gdist += crossSectionCalculator->getVar(4)
296 *(std::cos(phi)*theBeamPolarization.p3()*theTargetPolarization.p1()
297 + std::cos(phi)*theBeamPolarization.p1()*theTargetPolarization.p3()
298 + std::sin(phi)*theBeamPolarization.p3()*theTargetPolarization.p2()
299 + std::sin(phi)*theBeamPolarization.p2()*theTargetPolarization.p3());
300
301 treject = gdist/gdiced;
302 //G4cout<<" treject = "<<treject<<" at phi = "<<phi<<G4endl;
303 if (treject>1.+1.e-10 || treject<0){
304 G4cout<<"!!!ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
305 <<" phi rejection does not work properly: "<<treject<<G4endl;
306 G4cout<<" gdiced = "<<gdiced<<G4endl;
307 G4cout<<" gdist = "<<gdist<<G4endl;
308 G4cout<<" epsil = "<<epsil<<G4endl;
309 }
310
311 if (treject<1.e-3) {
312 G4cout<<"!!!ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
313 <<" phi rejection does not work properly: "<<treject<<"\n";
314 G4cout<<" gdiced="<<gdiced<<" gdist="<<gdist<<"\n";
315 G4cout<<" epsil = "<<epsil<<G4endl;
316 }
317
318 } while( treject < G4UniformRand() );
319 // G4cout<<"phi dicing END"<<G4endl;
320
321 G4double dirx = sint*std::cos(phi) , diry = sint*std::sin(phi) , dirz = cost;
322
323 //
324 // kinematic of the created pair
325 //
326 G4double TotalAvailableEnergy = PositKinEnergy + 2*electron_mass_c2;
327 G4double Phot1Energy = epsil*TotalAvailableEnergy;
328 G4double Phot2Energy =(1.-epsil)*TotalAvailableEnergy;
329
330 // *** prepare calculation of polarization transfer ***
331 G4ThreeVector Phot1Direction (dirx, diry, dirz);
332
333 // get interaction frame
334 G4ThreeVector nInteractionFrame =
335 G4PolarizationHelper::GetFrame(PositDirection,Phot1Direction);
336
337 // define proper in-plane and out-of-plane component of initial spins
338 theBeamPolarization.InvRotateAz(nInteractionFrame,PositDirection);
339 theTargetPolarization.InvRotateAz(nInteractionFrame,PositDirection);
340
341 // calculate spin transfere matrix
342
343 crossSectionCalculator->Initialize(epsil,gama,phi,theBeamPolarization,theTargetPolarization,2);
344
345 // **********************************************************************
346
347 Phot1Direction.rotateUz(PositDirection);
348 // create G4DynamicParticle object for the particle1
349 G4DynamicParticle* aParticle1= new G4DynamicParticle (G4Gamma::Gamma(),
350 Phot1Direction, Phot1Energy);
351 finalGamma1Polarization=crossSectionCalculator->GetPol2();
352 G4double n1=finalGamma1Polarization.mag2();
353 if (n1>1) {
354 G4cout<<"ERROR: PolarizedAnnihilation Polarization Vector at epsil = "
355 <<epsil<<" is too large!!! \n"
356 <<"annihi pol1= "<<finalGamma1Polarization<<", ("<<n1<<")\n";
357 finalGamma1Polarization+=1./std::sqrt(n1);
358 }
359
360 // define polarization of first final state photon
361 finalGamma1Polarization.SetPhoton();
362 finalGamma1Polarization.RotateAz(nInteractionFrame,Phot1Direction);
363 aParticle1->SetPolarization(finalGamma1Polarization.p1(),
364 finalGamma1Polarization.p2(),
365 finalGamma1Polarization.p3());
366
367 fvect->push_back(aParticle1);
368
369
370 // **********************************************************************
371
372 G4double Eratio= Phot1Energy/Phot2Energy;
373 G4double PositP= std::sqrt(PositKinEnergy*(PositKinEnergy+2.*electron_mass_c2));
374 G4ThreeVector Phot2Direction (-dirx*Eratio, -diry*Eratio,
375 (PositP-dirz*Phot1Energy)/Phot2Energy);
376 Phot2Direction.rotateUz(PositDirection);
377 // create G4DynamicParticle object for the particle2
378 G4DynamicParticle* aParticle2= new G4DynamicParticle (G4Gamma::Gamma(),
379 Phot2Direction, Phot2Energy);
380
381 // define polarization of second final state photon
382 finalGamma2Polarization=crossSectionCalculator->GetPol3();
383 G4double n2=finalGamma2Polarization.mag2();
384 if (n2>1) {
385 G4cout<<"ERROR: PolarizedAnnihilation Polarization Vector at epsil = "<<epsil<<" is too large!!! \n";
386 G4cout<<"annihi pol2= "<<finalGamma2Polarization<<", ("<<n2<<")\n";
387
388 finalGamma2Polarization+=1./std::sqrt(n2);
389 }
390 finalGamma2Polarization.SetPhoton();
391 finalGamma2Polarization.RotateAz(nInteractionFrame,Phot2Direction);
392 aParticle2->SetPolarization(finalGamma2Polarization.p1(),
393 finalGamma2Polarization.p2(),
394 finalGamma2Polarization.p3());
395
396 fvect->push_back(aParticle2);
397}
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