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G4RPGXiZeroInelastic.cc
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26 // $Id$
27 //
28 
29 #include "G4RPGXiZeroInelastic.hh"
30 #include "G4PhysicalConstants.hh"
31 #include "G4SystemOfUnits.hh"
32 #include "Randomize.hh"
33 
36  G4Nucleus& targetNucleus)
37 {
38  const G4HadProjectile *originalIncident = &aTrack;
39  if (originalIncident->GetKineticEnergy() <= 0.1*MeV) {
43  return &theParticleChange;
44  }
45 
46  // create the target particle
47  G4DynamicParticle* originalTarget = targetNucleus.ReturnTargetParticle();
48 
49  if (verboseLevel > 1) {
50  const G4Material *targetMaterial = aTrack.GetMaterial();
51  G4cout << "G4RPGXiZeroInelastic::ApplyYourself called" << G4endl;
52  G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy()/MeV << "MeV, ";
53  G4cout << "target material = " << targetMaterial->GetName() << ", ";
54  G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
55  << G4endl;
56  }
57 
58  // Fermi motion and evaporation
59  // As of Geant3, the Fermi energy calculation had not been Done
60  G4double ek = originalIncident->GetKineticEnergy()/MeV;
61  G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
62  G4ReactionProduct modifiedOriginal;
63  modifiedOriginal = *originalIncident;
64 
65  G4double tkin = targetNucleus.Cinema( ek );
66  ek += tkin;
67  modifiedOriginal.SetKineticEnergy( ek*MeV );
68  G4double et = ek + amas;
69  G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
70  G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
71  if( pp > 0.0 )
72  {
73  G4ThreeVector momentum = modifiedOriginal.GetMomentum();
74  modifiedOriginal.SetMomentum( momentum * (p/pp) );
75  }
76  //
77  // calculate black track energies
78  //
79  tkin = targetNucleus.EvaporationEffects( ek );
80  ek -= tkin;
81  modifiedOriginal.SetKineticEnergy( ek*MeV );
82  et = ek + amas;
83  p = std::sqrt( std::abs((et-amas)*(et+amas)) );
84  pp = modifiedOriginal.GetMomentum().mag()/MeV;
85  if( pp > 0.0 )
86  {
87  G4ThreeVector momentum = modifiedOriginal.GetMomentum();
88  modifiedOriginal.SetMomentum( momentum * (p/pp) );
89  }
90  G4ReactionProduct currentParticle = modifiedOriginal;
91  G4ReactionProduct targetParticle;
92  targetParticle = *originalTarget;
93  currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
94  targetParticle.SetSide( -1 ); // target always goes in backward hemisphere
95  G4bool incidentHasChanged = false;
96  G4bool targetHasChanged = false;
97  G4bool quasiElastic = false;
98  G4FastVector<G4ReactionProduct,GHADLISTSIZE> vec; // vec will contain the secondary particles
99  G4int vecLen = 0;
100  vec.Initialize( 0 );
101 
102  const G4double cutOff = 0.1;
103  if (currentParticle.GetKineticEnergy()/MeV > cutOff)
104  Cascade(vec, vecLen, originalIncident, currentParticle, targetParticle,
105  incidentHasChanged, targetHasChanged, quasiElastic);
106 
107  CalculateMomenta(vec, vecLen, originalIncident, originalTarget,
108  modifiedOriginal, targetNucleus, currentParticle,
109  targetParticle, incidentHasChanged, targetHasChanged,
110  quasiElastic);
111 
112  SetUpChange(vec, vecLen, currentParticle, targetParticle, incidentHasChanged);
113 
114  delete originalTarget;
115  return &theParticleChange;
116 }
117 
118 
119 void
120 G4RPGXiZeroInelastic::Cascade(G4FastVector<G4ReactionProduct,GHADLISTSIZE> &vec,
121  G4int& vecLen,
122  const G4HadProjectile* originalIncident,
123  G4ReactionProduct& currentParticle,
124  G4ReactionProduct& targetParticle,
125  G4bool& incidentHasChanged,
126  G4bool& targetHasChanged,
127  G4bool& quasiElastic)
128 {
129  // Derived from H. Fesefeldt's original FORTRAN code CASX0
130  //
131  // XiZero undergoes interaction with nucleon within a nucleus. Check if it is
132  // energetically possible to produce pions/kaons. In not, assume nuclear excitation
133  // occurs and input particle is degraded in energy. No other particles are produced.
134  // If reaction is possible, find the correct number of pions/protons/neutrons
135  // produced using an interpolation to multiplicity data. Replace some pions or
136  // protons/neutrons by kaons or strange baryons according to the average
137  // multiplicity per inelastic reaction.
138 
139  const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass()/MeV;
140  const G4double etOriginal = originalIncident->GetTotalEnergy()/MeV;
141  const G4double targetMass = targetParticle.GetMass()/MeV;
142  G4double centerofmassEnergy = std::sqrt(mOriginal*mOriginal +
143  targetMass*targetMass +
144  2.0*targetMass*etOriginal);
145  G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
146  if (availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass()/MeV) {
147  quasiElastic = true;
148  return;
149  }
150  static G4bool first = true;
151  const G4int numMul = 1200;
152  const G4int numSec = 60;
153  static G4double protmul[numMul], protnorm[numSec]; // proton constants
154  static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
155 
156  // np = number of pi+, nneg = number of pi-, nz = number of pi0
157  G4int counter, nt=0, np=0, nneg=0, nz=0;
158  G4double test;
159  const G4double c = 1.25;
160  const G4double b[] = { 0.7, 0.7 };
161  if (first) { // Computation of normalization constants will only be done once
162  first = false;
163  G4int i;
164  for (i = 0; i < numMul; ++i) protmul[i] = 0.0;
165  for (i = 0; i < numSec; ++i) protnorm[i] = 0.0;
166  counter = -1;
167  for( np=0; np<(numSec/3); ++np )
168  {
169  for( nneg=std::max(0,np-2); nneg<=(np+1); ++nneg )
170  {
171  for( nz=0; nz<numSec/3; ++nz )
172  {
173  if( ++counter < numMul )
174  {
175  nt = np+nneg+nz;
176  if( nt>0 && nt<=numSec )
177  {
178  protmul[counter] = Pmltpc(np,nneg,nz,nt,b[0],c);
179  protnorm[nt-1] += protmul[counter];
180  }
181  }
182  }
183  }
184  }
185  for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
186  for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
187  counter = -1;
188  for( np=0; np<numSec/3; ++np )
189  {
190  for( nneg=std::max(0,np-1); nneg<=(np+2); ++nneg )
191  {
192  for( nz=0; nz<numSec/3; ++nz )
193  {
194  if( ++counter < numMul )
195  {
196  nt = np+nneg+nz;
197  if( nt>0 && nt<=numSec )
198  {
199  neutmul[counter] = Pmltpc(np,nneg,nz,nt,b[1],c);
200  neutnorm[nt-1] += neutmul[counter];
201  }
202  }
203  }
204  }
205  }
206  for( i=0; i<numSec; ++i )
207  {
208  if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
209  if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
210  }
211  } // end of initialization
212 
213  const G4double expxu = 82.; // upper bound for arg. of exp
214  const G4double expxl = -expxu; // lower bound for arg. of exp
220  //
221  // energetically possible to produce pion(s) --> inelastic scattering
222  //
223  G4double n, anpn;
224  GetNormalizationConstant( availableEnergy, n, anpn );
225  G4double ran = G4UniformRand();
226  G4double dum, excs = 0.0;
227  if( targetParticle.GetDefinition() == aProton )
228  {
229  counter = -1;
230  for( np=0; np<numSec/3 && ran>=excs; ++np )
231  {
232  for( nneg=std::max(0,np-2); nneg<=(np+1) && ran>=excs; ++nneg )
233  {
234  for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
235  {
236  if( ++counter < numMul )
237  {
238  nt = np+nneg+nz;
239  if( nt>0 && nt<=numSec )
240  {
241  test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
242  dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
243  if( std::fabs(dum) < 1.0 )
244  {
245  if( test >= 1.0e-10 )excs += dum*test;
246  }
247  else
248  excs += dum*test;
249  }
250  }
251  }
252  }
253  }
254  if( ran >= excs ) // 3 previous loops continued to the end
255  {
256  quasiElastic = true;
257  return;
258  }
259  np--; nneg--; nz--;
260  //
261  // number of secondary mesons determined by kno distribution
262  // check for total charge of final state mesons to determine
263  // the kind of baryons to be produced, taking into account
264  // charge and strangeness conservation
265  //
266  if( np < nneg+1 )
267  {
268  if( np != nneg ) // charge mismatch
269  {
270  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
271  incidentHasChanged = true;
272  //
273  // correct the strangeness by replacing a pi- by a kaon-
274  //
275  vec.Initialize( 1 );
277  p->SetDefinition( aKaonMinus );
278  (G4UniformRand() < 0.5) ? p->SetSide( -1 ) : p->SetSide( 1 );
279  vec.SetElement( vecLen++, p );
280  --nneg;
281  }
282  }
283  else if( np == nneg+1 )
284  {
285  if( G4UniformRand() < 0.5 )
286  {
287  targetParticle.SetDefinitionAndUpdateE( aNeutron );
288  targetHasChanged = true;
289  }
290  else
291  {
292  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
293  incidentHasChanged = true;
294  }
295  }
296  else
297  {
298  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
299  incidentHasChanged = true;
300  targetParticle.SetDefinitionAndUpdateE( aNeutron );
301  targetHasChanged = true;
302  }
303  }
304  else // target must be a neutron
305  {
306  counter = -1;
307  for( np=0; np<numSec/3 && ran>=excs; ++np )
308  {
309  for( nneg=std::max(0,np-1); nneg<=(np+2) && ran>=excs; ++nneg )
310  {
311  for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
312  {
313  if( ++counter < numMul )
314  {
315  nt = np+nneg+nz;
316  if( nt>0 && nt<=numSec )
317  {
318  test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
319  dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
320  if( std::fabs(dum) < 1.0 )
321  {
322  if( test >= 1.0e-10 )excs += dum*test;
323  }
324  else
325  excs += dum*test;
326  }
327  }
328  }
329  }
330  }
331  if( ran >= excs ) // 3 previous loops continued to the end
332  {
333  quasiElastic = true;
334  return;
335  }
336  np--; nneg--; nz--;
337  if( np < nneg )
338  {
339  if( np+1 == nneg )
340  {
341  targetParticle.SetDefinitionAndUpdateE( aProton );
342  targetHasChanged = true;
343  }
344  else // charge mismatch
345  {
346  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
347  incidentHasChanged = true;
348  targetParticle.SetDefinitionAndUpdateE( aProton );
349  targetHasChanged = true;
350  //
351  // correct the strangeness by replacing a pi- by a kaon-
352  //
353  vec.Initialize( 1 );
355  p->SetDefinition( aKaonMinus );
356  (G4UniformRand() < 0.5) ? p->SetSide( -1 ) : p->SetSide( 1 );
357  vec.SetElement( vecLen++, p );
358  --nneg;
359  }
360  }
361  else if( np == nneg )
362  {
363  if( G4UniformRand() >= 0.5 )
364  {
365  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
366  incidentHasChanged = true;
367  targetParticle.SetDefinitionAndUpdateE( aProton );
368  targetHasChanged = true;
369  }
370  }
371  else
372  {
373  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
374  incidentHasChanged = true;
375  }
376  }
377 
378  SetUpPions(np, nneg, nz, vec, vecLen);
379  return;
380 }
381 
382  /* end of file */
383