source: trunk/source/processes/electromagnetic/polarisation/src/G4PolarizedAnnihilationModel.cc @ 1244

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26// $Id: G4PolarizedAnnihilationModel.cc,v 1.9 2009/11/12 12:57:15 schaelic Exp $
27// GEANT4 tag $Name: geant4-09-03 $
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  gParticleChange = GetParticleChangeForGamma();
86  gIsInitialised = true;
87}
88
89G4double G4PolarizedAnnihilationModel::ComputeCrossSectionPerElectron(
90                                const G4ParticleDefinition* pd,
91                                      G4double kinEnergy, 
92                                      G4double cut,
93                                      G4double emax)
94{
95  G4double xs = G4eeToTwoGammaModel::ComputeCrossSectionPerElectron(pd,kinEnergy,
96                                                                cut,emax);
97
98  G4double polzz = theBeamPolarization.z()*theTargetPolarization.z();
99  G4double poltt = theBeamPolarization.x()*theTargetPolarization.x() 
100                 + theBeamPolarization.y()*theTargetPolarization.y();
101  if (polzz!=0 || poltt!=0) {
102    G4double xval,lasym,tasym;
103    ComputeAsymmetriesPerElectron(kinEnergy,xval,lasym,tasym);
104    xs*=(1.+polzz*lasym+poltt*tasym);
105  }
106
107  return xs;
108}
109
110void G4PolarizedAnnihilationModel::ComputeAsymmetriesPerElectron(G4double ene,
111                                               G4double & valueX,
112                                               G4double & valueA,
113                                               G4double & valueT)
114{
115  // *** calculate asymmetries
116  G4double gam = 1. + ene/electron_mass_c2;
117  G4double xs0=crossSectionCalculator->TotalXSection(0.,1.,gam,
118                                               G4StokesVector::ZERO,
119                                               G4StokesVector::ZERO);
120  G4double xsA=crossSectionCalculator->TotalXSection(0.,1.,gam,
121                                               G4StokesVector::P3,
122                                               G4StokesVector::P3);
123  G4double xsT1=crossSectionCalculator->TotalXSection(0.,1.,gam,
124                                               G4StokesVector::P1,
125                                               G4StokesVector::P1);
126  G4double xsT2=crossSectionCalculator->TotalXSection(0.,1.,gam,
127                                               G4StokesVector::P2,
128                                               G4StokesVector::P2);
129  G4double xsT=0.5*(xsT1+xsT2);
130 
131  valueX=xs0;
132  valueA=xsA/xs0-1.;
133  valueT=xsT/xs0-1.;
134  //  G4cout<<valueX<<"\t"<<valueA<<"\t"<<valueT<<"   energy = "<<gam<<G4endl;
135  if ( (valueA < -1) || (1 < valueA)) {
136    G4cout<< " ERROR PolarizedAnnihilationPS::ComputeAsymmetries \n";
137    G4cout<< " something wrong in total cross section calculation (valueA)\n";
138    G4cout<<"*********** LONG "<<valueX<<"\t"<<valueA<<"\t"<<valueT<<"   energy = "<<gam<<G4endl;
139  }
140  if ( (valueT < -1) || (1 < valueT)) {
141    G4cout<< " ERROR PolarizedAnnihilationPS::ComputeAsymmetries \n";
142    G4cout<< " something wrong in total cross section calculation (valueT)\n";
143    G4cout<<"****** TRAN "<<valueX<<"\t"<<valueA<<"\t"<<valueT<<"   energy = "<<gam<<G4endl;
144  }
145}
146
147
148void G4PolarizedAnnihilationModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
149                                                     const G4MaterialCutsCouple* /*couple*/,
150                                                     const G4DynamicParticle* dp,
151                                                     G4double /*tmin*/,
152                                                     G4double /*maxEnergy*/) 
153{
154//   G4ParticleChangeForGamma*  gParticleChange
155//     = dynamic_cast<G4ParticleChangeForGamma*>(pParticleChange);
156  const G4Track * aTrack = gParticleChange->GetCurrentTrack();
157
158  // kill primary
159  gParticleChange->SetProposedKineticEnergy(0.);
160  gParticleChange->ProposeTrackStatus(fStopAndKill);
161
162  // V.Ivanchenko add protection against zero kin energy
163  G4double PositKinEnergy = dp->GetKineticEnergy();
164
165  if(PositKinEnergy < DBL_MIN) {
166
167    G4double cosTeta = 2.*G4UniformRand()-1.;
168    G4double sinTeta = std::sqrt((1.0 - cosTeta)*(1.0 + cosTeta));
169    G4double phi     = twopi * G4UniformRand();
170    G4ThreeVector dir(sinTeta*std::cos(phi), sinTeta*std::sin(phi), cosTeta);
171    fvect->push_back( new G4DynamicParticle(G4Gamma::Gamma(), dir, electron_mass_c2));
172    fvect->push_back( new G4DynamicParticle(G4Gamma::Gamma(),-dir, electron_mass_c2));
173    return;
174  }
175
176  // *** obtain and save target and beam polarization ***
177  G4PolarizationManager * polarizationManager = G4PolarizationManager::GetInstance();
178
179  // obtain polarization of the beam
180  theBeamPolarization = aTrack->GetPolarization();
181
182  // obtain polarization of the media
183  G4VPhysicalVolume*  aPVolume  = aTrack->GetVolume();
184  G4LogicalVolume*    aLVolume  = aPVolume->GetLogicalVolume();
185  const G4bool targetIsPolarized = polarizationManager->IsPolarized(aLVolume);
186  theTargetPolarization = polarizationManager->GetVolumePolarization(aLVolume);
187
188  // transfer target electron polarization in frame of positron
189  if (targetIsPolarized)
190      theTargetPolarization.rotateUz(dp->GetMomentumDirection());
191 
192  G4ParticleMomentum PositDirection = dp->GetMomentumDirection();
193
194  // polar asymmetry:
195  G4double polarization = theBeamPolarization.p3()*theTargetPolarization.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. , sqg2m1 = std::sqrt(gamam1*gamap1);
200
201  // limits of the energy sampling
202  G4double epsilmin = 0.5 - sqgrate , epsilmax = 0.5 + sqgrate;
203  G4double epsilqot = epsilmax/epsilmin;
204 
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  //
210  G4double epsil;
211  G4double gmax=1. + std::fabs(polarization); // crude estimate
212
213  G4bool check_range=true;
214
215  crossSectionCalculator->Initialize(epsilmin, gama, 0.,  theBeamPolarization, theTargetPolarization);
216  if (crossSectionCalculator->DiceEpsilon()<0) {
217    G4cout<<"ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
218          <<"epsilmin DiceRoutine not appropriate ! "<<crossSectionCalculator->DiceEpsilon()<<G4endl;
219    check_range=false;
220  }
221
222  crossSectionCalculator->Initialize(epsilmax, gama, 0.,  theBeamPolarization, theTargetPolarization);
223  if (crossSectionCalculator->DiceEpsilon()<0) {
224    G4cout<<"ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
225          <<"epsilmax DiceRoutine not appropriate ! "<<crossSectionCalculator->DiceEpsilon()<<G4endl;
226    check_range=false;
227  }
228
229  G4int ncount=0;
230  G4double trejectmax=0.;
231  G4double treject;
232
233
234  do {
235    //
236    epsil = epsilmin*std::pow(epsilqot,G4UniformRand());
237
238    crossSectionCalculator->Initialize(epsil, gama, 0., theBeamPolarization, theTargetPolarization,1);
239
240    treject = crossSectionCalculator->DiceEpsilon(); 
241    treject*=epsil;
242
243    if (treject>gmax  || treject<0.) 
244      G4cout<<"ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
245            <<" eps ("<<epsil<<") rejection does not work properly: "<<treject<<G4endl;
246    ++ncount;
247    if (treject>trejectmax) trejectmax=treject;
248    if (ncount>1000) {
249      G4cout<<"WARNING  in PolarizedAnnihilationPS::PostStepDoIt\n"
250            <<"eps dicing very inefficient ="<<trejectmax/gmax
251            <<", "<<treject/gmax<<".  For secondary energy = "<<epsil<<"   "<<ncount<<G4endl;
252      break;
253    }
254
255  } while( treject < gmax*G4UniformRand() );
256
257  //
258  // scattered Gamma angles. ( Z - axis along the parent positron)
259  //
260   
261  G4double cost = (epsil*gamap1-1.)/(epsil*sqg2m1);
262  G4double sint = std::sqrt((1.+cost)*(1.-cost));
263  G4double phi  = 0.;
264  G4double   beamTrans = std::sqrt(sqr(theBeamPolarization.p1()) + sqr(theBeamPolarization.p2()));
265  G4double targetTrans = std::sqrt(sqr(theTargetPolarization.p1()) + sqr(theTargetPolarization.p2()));
266
267  //  G4cout<<"phi dicing START"<<G4endl;
268  do{
269    phi  = twopi * G4UniformRand();
270    crossSectionCalculator->Initialize(epsil, gama, 0., theBeamPolarization, theTargetPolarization,2);
271
272    G4double gdiced =crossSectionCalculator->getVar(0);
273    gdiced += crossSectionCalculator->getVar(3)*theBeamPolarization.p3()*theTargetPolarization.p3();
274    gdiced += 1.*(std::fabs(crossSectionCalculator->getVar(1)) 
275                  + std::fabs(crossSectionCalculator->getVar(2)))*beamTrans*targetTrans;
276    gdiced += 1.*std::fabs(crossSectionCalculator->getVar(4))
277      *(std::fabs(theBeamPolarization.p3())*targetTrans + std::fabs(theTargetPolarization.p3())*beamTrans);
278
279    G4double gdist = crossSectionCalculator->getVar(0);
280    gdist += crossSectionCalculator->getVar(3)*theBeamPolarization.p3()*theTargetPolarization.p3();
281    gdist += crossSectionCalculator->getVar(1)*(std::cos(phi)*theBeamPolarization.p1() 
282                                                + std::sin(phi)*theBeamPolarization.p2())
283                                              *(std::cos(phi)*theTargetPolarization.p1() 
284                                                + std::sin(phi)*theTargetPolarization.p2());
285    gdist += crossSectionCalculator->getVar(2)*(std::cos(phi)*theBeamPolarization.p2() 
286                                                - std::sin(phi)*theBeamPolarization.p1())
287                                              *(std::cos(phi)*theTargetPolarization.p2() 
288                                                - std::sin(phi)*theTargetPolarization.p1());
289    gdist += crossSectionCalculator->getVar(4)
290      *(std::cos(phi)*theBeamPolarization.p3()*theTargetPolarization.p1()
291        + std::cos(phi)*theBeamPolarization.p1()*theTargetPolarization.p3() 
292        + std::sin(phi)*theBeamPolarization.p3()*theTargetPolarization.p2() 
293        + std::sin(phi)*theBeamPolarization.p2()*theTargetPolarization.p3());
294
295    treject = gdist/gdiced;
296    //G4cout<<" treject = "<<treject<<" at phi = "<<phi<<G4endl;
297     if (treject>1.+1.e-10 || treject<0){
298       G4cout<<"!!!ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
299             <<" phi rejection does not work properly: "<<treject<<G4endl;
300       G4cout<<" gdiced = "<<gdiced<<G4endl;
301       G4cout<<" gdist = "<<gdist<<G4endl;
302       G4cout<<" epsil = "<<epsil<<G4endl;
303     }
304     
305     if (treject<1.e-3) {
306       G4cout<<"!!!ERROR in PolarizedAnnihilationPS::PostStepDoIt\n"
307            <<" phi rejection does not work properly: "<<treject<<"\n";
308       G4cout<<" gdiced="<<gdiced<<"   gdist="<<gdist<<"\n";
309       G4cout<<" epsil = "<<epsil<<G4endl;
310     }
311
312  } while( treject < G4UniformRand() );
313  //  G4cout<<"phi dicing END"<<G4endl;
314
315  G4double dirx = sint*std::cos(phi) , diry = sint*std::sin(phi) , dirz = cost;
316
317  //
318  // kinematic of the created pair
319  //
320  G4double TotalAvailableEnergy = PositKinEnergy + 2*electron_mass_c2;
321  G4double Phot1Energy = epsil*TotalAvailableEnergy;
322  G4double Phot2Energy =(1.-epsil)*TotalAvailableEnergy;
323
324  // *** prepare calculation of polarization transfer ***
325  G4ThreeVector Phot1Direction (dirx, diry, dirz);
326
327  // get interaction frame
328  G4ThreeVector  nInteractionFrame = 
329    G4PolarizationHelper::GetFrame(PositDirection,Phot1Direction);
330     
331  // define proper in-plane and out-of-plane component of initial spins
332  theBeamPolarization.InvRotateAz(nInteractionFrame,PositDirection);
333  theTargetPolarization.InvRotateAz(nInteractionFrame,PositDirection);
334
335  // calculate spin transfere matrix
336
337  crossSectionCalculator->Initialize(epsil,gama,phi,theBeamPolarization,theTargetPolarization,2);
338
339  // **********************************************************************
340
341  Phot1Direction.rotateUz(PositDirection);   
342  // create G4DynamicParticle object for the particle1 
343  G4DynamicParticle* aParticle1= new G4DynamicParticle (G4Gamma::Gamma(),
344                                                        Phot1Direction, Phot1Energy);
345  finalGamma1Polarization=crossSectionCalculator->GetPol2();
346  G4double n1=finalGamma1Polarization.mag2();
347  if (n1>1) {
348    G4cout<<"ERROR: PolarizedAnnihilation Polarization Vector at epsil = "
349          <<epsil<<" is too large!!! \n"
350          <<"annihi pol1= "<<finalGamma1Polarization<<", ("<<n1<<")\n";
351    finalGamma1Polarization*=1./std::sqrt(n1);
352  }
353
354  // define polarization of first final state photon
355  finalGamma1Polarization.SetPhoton();
356  finalGamma1Polarization.RotateAz(nInteractionFrame,Phot1Direction);
357  aParticle1->SetPolarization(finalGamma1Polarization.p1(),
358                              finalGamma1Polarization.p2(),
359                              finalGamma1Polarization.p3());
360
361  fvect->push_back(aParticle1);
362
363
364  // **********************************************************************
365
366  G4double Eratio= Phot1Energy/Phot2Energy;
367  G4double PositP= std::sqrt(PositKinEnergy*(PositKinEnergy+2.*electron_mass_c2));
368  G4ThreeVector Phot2Direction (-dirx*Eratio, -diry*Eratio,
369                                (PositP-dirz*Phot1Energy)/Phot2Energy); 
370  Phot2Direction.rotateUz(PositDirection); 
371  // create G4DynamicParticle object for the particle2
372  G4DynamicParticle* aParticle2= new G4DynamicParticle (G4Gamma::Gamma(),
373                                                        Phot2Direction, Phot2Energy);
374
375  // define polarization of second final state photon
376  finalGamma2Polarization=crossSectionCalculator->GetPol3();
377  G4double n2=finalGamma2Polarization.mag2();
378  if (n2>1) {
379    G4cout<<"ERROR: PolarizedAnnihilation Polarization Vector at epsil = "<<epsil<<" is too large!!! \n";
380    G4cout<<"annihi pol2= "<<finalGamma2Polarization<<", ("<<n2<<")\n";
381   
382    finalGamma2Polarization*=1./std::sqrt(n2);
383  }
384  finalGamma2Polarization.SetPhoton();
385  finalGamma2Polarization.RotateAz(nInteractionFrame,Phot2Direction);
386  aParticle2->SetPolarization(finalGamma2Polarization.p1(),
387                              finalGamma2Polarization.p2(),
388                              finalGamma2Polarization.p3());
389
390  fvect->push_back(aParticle2);
391}
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