source: trunk/source/processes/hadronic/models/rpg/src/G4RPGNeutronInelastic.cc @ 1055

Last change on this file since 1055 was 1007, checked in by garnier, 15 years ago

update to geant4.9.2
File size: 12.5 KB
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26// $Id: G4RPGNeutronInelastic.cc,v 1.4 2008/05/05 21:21:55 dennis Exp $
27// GEANT4 tag $Name: geant4-09-02 $
28//
29 
30#include "G4RPGNeutronInelastic.hh"
31#include "Randomize.hh"
32
33
34G4HadFinalState* 
35G4RPGNeutronInelastic::ApplyYourself(const G4HadProjectile& aTrack,
36                                      G4Nucleus& targetNucleus)
37{
38  theParticleChange.Clear();
39  const G4HadProjectile* originalIncident = &aTrack;
40
41  //
42  // create the target particle
43  //
44  G4DynamicParticle* originalTarget = targetNucleus.ReturnTargetParticle();
45 
46  G4ReactionProduct modifiedOriginal;
47  modifiedOriginal = *originalIncident;
48  G4ReactionProduct targetParticle;
49  targetParticle = *originalTarget;
50  if( originalIncident->GetKineticEnergy()/GeV < 0.01 + 2.*G4UniformRand()/9. )
51  {
52    SlowNeutron(originalIncident,modifiedOriginal,targetParticle,targetNucleus );
53    delete originalTarget;
54    return &theParticleChange;
55  }
56
57  //
58  // Fermi motion and evaporation
59  // As of Geant3, the Fermi energy calculation had not been Done
60  //
61  G4double ek = originalIncident->GetKineticEnergy()/MeV;
62  G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
63   
64  G4double tkin = targetNucleus.Cinema( ek );
65  ek += tkin;
66  modifiedOriginal.SetKineticEnergy( ek*MeV );
67  G4double et = ek + amas;
68  G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
69  G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
70  if( pp > 0.0 )
71  {
72    G4ThreeVector momentum = modifiedOriginal.GetMomentum();
73    modifiedOriginal.SetMomentum( momentum * (p/pp) );
74  }
75  //
76  // calculate black track energies
77  //
78  tkin = targetNucleus.EvaporationEffects( ek );
79  ek -= tkin;
80  modifiedOriginal.SetKineticEnergy(ek);
81  et = ek + amas;
82  p = std::sqrt( std::abs((et-amas)*(et+amas)) );
83  pp = modifiedOriginal.GetMomentum().mag();
84  if( pp > 0.0 )
85  {
86    G4ThreeVector momentum = modifiedOriginal.GetMomentum();
87    modifiedOriginal.SetMomentum( momentum * (p/pp) );
88  }
89  const G4double cutOff = 0.1;
90  if( modifiedOriginal.GetKineticEnergy()/MeV <= cutOff )
91  {
92    SlowNeutron( originalIncident, modifiedOriginal, targetParticle, targetNucleus );
93    delete originalTarget;
94    return &theParticleChange;
95  }
96
97  G4ReactionProduct currentParticle = modifiedOriginal;
98  currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
99  targetParticle.SetSide( -1 );  // target always goes in backward hemisphere
100  G4bool incidentHasChanged = false;
101  G4bool targetHasChanged = false;
102  G4bool quasiElastic = false;
103  G4FastVector<G4ReactionProduct,256> vec;  // vec will contain sec. particles
104  G4int vecLen = 0;
105  vec.Initialize( 0 );
106   
107  InitialCollision(vec, vecLen, currentParticle, targetParticle,
108                   incidentHasChanged, targetHasChanged);
109   
110  CalculateMomenta(vec, vecLen,
111                   originalIncident, originalTarget, modifiedOriginal,
112                   targetNucleus, currentParticle, targetParticle,
113                   incidentHasChanged, targetHasChanged, quasiElastic);
114   
115  SetUpChange(vec, vecLen,
116              currentParticle, targetParticle,
117              incidentHasChanged);
118   
119  delete originalTarget;
120  return &theParticleChange;
121}
122 
123void
124G4RPGNeutronInelastic::SlowNeutron(const G4HadProjectile* originalIncident,
125                              G4ReactionProduct& modifiedOriginal,
126                              G4ReactionProduct& targetParticle,
127                              G4Nucleus& targetNucleus)
128{       
129  const G4double A = targetNucleus.GetN();    // atomic weight
130  const G4double Z = targetNucleus.GetZ();    // atomic number
131   
132  G4double currentKinetic = modifiedOriginal.GetKineticEnergy()/MeV;
133  G4double currentMass = modifiedOriginal.GetMass()/MeV;
134  if( A < 1.5 )   // Hydrogen
135  {
136    //
137    // very simple simulation of scattering angle and energy
138    // nonrelativistic approximation with isotropic angular
139    // distribution in the cms system
140    //
141    G4double cost1, eka = 0.0;
142    while (eka <= 0.0)
143    {
144      cost1 = -1.0 + 2.0*G4UniformRand();
145      eka = 1.0 + 2.0*cost1*A + A*A;
146    }
147    G4double cost = std::min( 1.0, std::max( -1.0, (A*cost1+1.0)/std::sqrt(eka) ) );
148    eka /= (1.0+A)*(1.0+A);
149    G4double ek = currentKinetic*MeV/GeV;
150    G4double amas = currentMass*MeV/GeV;
151    ek *= eka;
152    G4double en = ek + amas;
153    G4double p = std::sqrt(std::abs(en*en-amas*amas));
154    G4double sint = std::sqrt(std::abs(1.0-cost*cost));
155    G4double phi = G4UniformRand()*twopi;
156    G4double px = sint*std::sin(phi);
157    G4double py = sint*std::cos(phi);
158    G4double pz = cost;
159    targetParticle.SetMomentum( px*GeV, py*GeV, pz*GeV );
160    G4double pxO = originalIncident->Get4Momentum().x()/GeV;
161    G4double pyO = originalIncident->Get4Momentum().y()/GeV;
162    G4double pzO = originalIncident->Get4Momentum().z()/GeV;
163    G4double ptO = pxO*pxO + pyO+pyO;
164    if( ptO > 0.0 )
165    {
166      G4double pO = std::sqrt(pxO*pxO+pyO*pyO+pzO*pzO);
167      cost = pzO/pO;
168      sint = 0.5*(std::sqrt(std::abs((1.0-cost)*(1.0+cost)))+std::sqrt(ptO)/pO);
169      G4double ph = pi/2.0;
170      if( pyO < 0.0 )ph = ph*1.5;
171      if( std::abs(pxO) > 0.000001 )ph = std::atan2(pyO,pxO);
172      G4double cosp = std::cos(ph);
173      G4double sinp = std::sin(ph);
174      px = cost*cosp*px - sinp*py+sint*cosp*pz;
175      py = cost*sinp*px + cosp*py+sint*sinp*pz;
176      pz = -sint*px     + cost*pz;
177    }
178    else
179    {
180      if( pz < 0.0 )pz *= -1.0;
181    }
182    G4double pu = std::sqrt(px*px+py*py+pz*pz);
183    modifiedOriginal.SetMomentum( targetParticle.GetMomentum() * (p/pu) );
184    modifiedOriginal.SetKineticEnergy( ek*GeV );
185     
186    targetParticle.SetMomentum(
187     originalIncident->Get4Momentum().vect() - modifiedOriginal.GetMomentum() );
188    G4double pp = targetParticle.GetMomentum().mag();
189    G4double tarmas = targetParticle.GetMass();
190    targetParticle.SetTotalEnergy( std::sqrt( pp*pp + tarmas*tarmas ) );
191     
192    theParticleChange.SetEnergyChange( modifiedOriginal.GetKineticEnergy() );
193    G4DynamicParticle *pd = new G4DynamicParticle;
194    pd->SetDefinition( targetParticle.GetDefinition() );
195    pd->SetMomentum( targetParticle.GetMomentum() );
196    theParticleChange.AddSecondary( pd );
197    return;
198  }
199
200  G4FastVector<G4ReactionProduct,4> vec;  // vec will contain the secondary particles
201  G4int vecLen = 0;
202  vec.Initialize( 0 );
203   
204  G4double theAtomicMass = targetNucleus.AtomicMass( A, Z );
205  G4double massVec[9];
206  massVec[0] = targetNucleus.AtomicMass( A+1.0, Z     );
207  massVec[1] = theAtomicMass;
208  massVec[2] = 0.;
209  if (Z > 1.0) massVec[2] = targetNucleus.AtomicMass(A, Z-1.0);
210  massVec[3] = 0.;
211  if (Z > 1.0 && A > 1.0) massVec[3] = targetNucleus.AtomicMass(A-1.0, Z-1.0 );
212  massVec[4] = 0.;
213  if (Z > 1.0 && A > 2.0 && A-2.0 > Z-1.0)
214    massVec[4] = targetNucleus.AtomicMass( A-2.0, Z-1.0 );
215  massVec[5] = 0.;
216  if (Z > 2.0 && A > 3.0 && A-3.0 > Z-2.0)
217    massVec[5] = targetNucleus.AtomicMass( A-3.0, Z-2.0 );
218  massVec[6] = 0.;
219  if (A > 1.0 && A-1.0 > Z) massVec[6] = targetNucleus.AtomicMass(A-1.0, Z);
220  massVec[7] = massVec[3];
221  massVec[8] = 0.;
222  if (Z > 2.0 && A > 1.0) massVec[8] = targetNucleus.AtomicMass( A-1.0,Z-2.0 );
223   
224  twoBody.NuclearReaction(vec, vecLen, originalIncident,
225                          targetNucleus, theAtomicMass, massVec );
226   
227  theParticleChange.SetStatusChange( stopAndKill );
228  theParticleChange.SetEnergyChange( 0.0 );
229   
230  G4DynamicParticle* pd;
231  for( G4int i=0; i<vecLen; ++i ) {
232    pd = new G4DynamicParticle();
233    pd->SetDefinition( vec[i]->GetDefinition() );
234    pd->SetMomentum( vec[i]->GetMomentum() );
235    theParticleChange.AddSecondary( pd );
236    delete vec[i];
237  }
238}
239
240
241// Initial Collision
242//   selects the particle types arising from the initial collision of
243//   the neutron and target nucleon.  Secondaries are assigned to
244//   forward and backward reaction hemispheres, but final state energies
245//   and momenta are not calculated here.
246
247void
248G4RPGNeutronInelastic::InitialCollision(G4FastVector<G4ReactionProduct,256>& vec,
249                                   G4int& vecLen,
250                                   G4ReactionProduct& currentParticle,
251                                   G4ReactionProduct& targetParticle,
252                                   G4bool& incidentHasChanged,
253                                   G4bool& targetHasChanged)
254{
255  G4double KE = currentParticle.GetKineticEnergy()/GeV;
256 
257  G4int mult;
258  G4int partType;
259  std::vector<G4int> fsTypes;
260  G4int part1;
261  G4int part2;
262 
263  G4double testCharge;
264  G4double testBaryon;
265  G4double testStrange;
266 
267  // Get particle types according to incident and target types
268
269  if (targetParticle.GetDefinition() == particleDef[neu]) {
270    mult = GetMultiplicityT1(KE);
271    fsTypes = GetFSPartTypesForNN(mult, KE);
272
273    part1 = fsTypes[0];
274    part2 = fsTypes[1];
275    currentParticle.SetDefinition(particleDef[part1]);
276    targetParticle.SetDefinition(particleDef[part2]);
277    if (part1 == pro) {     
278      if (part2 == neu) {
279        if (G4UniformRand() > 0.5) {
280          incidentHasChanged = true;
281        } else {
282          targetHasChanged = true;
283          currentParticle.SetDefinition(particleDef[part2]);
284          targetParticle.SetDefinition(particleDef[part1]);
285        }
286      } else {
287        targetHasChanged = true;
288        incidentHasChanged = true;
289      }
290
291    } else { // neutron
292      if (part2 > neu && part2 < xi0) targetHasChanged = true;
293    }
294
295    testCharge = 0.0;
296    testBaryon = 2.0;
297    testStrange = 0.0;
298
299  } else { // target was a proton
300    mult = GetMultiplicityT0(KE);
301    fsTypes = GetFSPartTypesForNP(mult, KE);
302 
303    part1 = fsTypes[0];
304    part2 = fsTypes[1];
305    currentParticle.SetDefinition(particleDef[part1]);
306    targetParticle.SetDefinition(particleDef[part2]);
307    if (part1 == pro) {
308      if (part2 == pro) {
309        incidentHasChanged = true;
310      } else if (part2 == neu) {
311        if (G4UniformRand() > 0.5) {
312          incidentHasChanged = true;
313          targetHasChanged = true;
314        } else {
315          currentParticle.SetDefinition(particleDef[part2]);
316          targetParticle.SetDefinition(particleDef[part1]);
317        }
318       
319      } else if (part2 > neu && part2 < xi0) {
320        incidentHasChanged = true;
321        targetHasChanged = true;
322      }
323
324    } else { // neutron
325      targetHasChanged = true;
326    }
327
328    testCharge = 1.0;
329    testBaryon = 2.0;
330    testStrange = 0.0;
331  }
332
333  //  if (mult == 2 && !incidentHasChanged && !targetHasChanged)
334  //                                              quasiElastic = true;
335 
336  // Remove incident and target from fsTypes
337 
338  fsTypes.erase(fsTypes.begin());
339  fsTypes.erase(fsTypes.begin());
340
341  // Remaining particles are secondaries.  Put them into vec.
342 
343  G4ReactionProduct* rp(0);
344  for(G4int i=0; i < mult-2; ++i ) {
345    partType = fsTypes[i];
346    rp = new G4ReactionProduct();
347    rp->SetDefinition(particleDef[partType]);
348    (G4UniformRand() < 0.5) ? rp->SetSide(-1) : rp->SetSide(1);
349    vec.SetElement(vecLen++, rp);
350  }
351
352  // Check conservation of charge, strangeness, baryon number
353 
354  CheckQnums(vec, vecLen, currentParticle, targetParticle,
355             testCharge, testBaryon, testStrange);
356 
357  return;
358}
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