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G4LEAntiXiZeroInelastic.cc
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26 // $Id$
27 //
28 // Hadronic Process: AntiXiZero Inelastic Process
29 // J.L. Chuma, TRIUMF, 20-Feb-1997
30 // Modified by J.L.Chuma 30-Apr-97: added originalTarget for CalculateMomenta
31 //
32 // NOTE: The FORTRAN version of the cascade, CASAXO, simply called the
33 // routine for the XiZero particle. Hence, the ApplyYourself function
34 // below is just a copy of the ApplyYourself from the XiZero particle.
35 
37 #include "G4PhysicalConstants.hh"
38 #include "G4SystemOfUnits.hh"
39 #include "Randomize.hh"
40 
42 {
43  outFile << "G4LEAntiXiZeroInelastic is one of the Low Energy Parameterized\n"
44  << "(LEP) models used to implement inelastic antiXi0 scattering\n"
45  << "from nuclei. It is a re-engineered version of the GHEISHA\n"
46  << "code of H. Fesefeldt. It divides the initial collision\n"
47  << "products into backward- and forward-going clusters which are\n"
48  << "then decayed into final state hadrons. The model does not\n"
49  << "conserve energy on an event-by-event basis. It may be\n"
50  << "applied to antiXi0 with initial energies between 0 and 25\n"
51  << "GeV.\n";
52 }
53 
56  G4Nucleus& targetNucleus)
57 {
58  const G4HadProjectile *originalIncident = &aTrack;
59 
60  // create the target particle
61  G4DynamicParticle* originalTarget = targetNucleus.ReturnTargetParticle();
62 
63  if (verboseLevel > 1) {
64  const G4Material *targetMaterial = aTrack.GetMaterial();
65  G4cout << "G4LEAntiXiZeroInelastic::ApplyYourself called" << G4endl;
66  G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy()/MeV << "MeV, ";
67  G4cout << "target material = " << targetMaterial->GetName() << ", ";
68  G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
69  << G4endl;
70  }
71 
72  // Fermi motion and evaporation
73  // As of Geant3, the Fermi energy calculation had not been Done
74  G4double ek = originalIncident->GetKineticEnergy()/MeV;
75  G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
76  G4ReactionProduct modifiedOriginal;
77  modifiedOriginal = *originalIncident;
78 
79  G4double tkin = targetNucleus.Cinema( ek );
80  ek += tkin;
81  modifiedOriginal.SetKineticEnergy( ek*MeV );
82  G4double et = ek + amas;
83  G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
84  G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
85  if (pp > 0.0) {
86  G4ThreeVector momentum = modifiedOriginal.GetMomentum();
87  modifiedOriginal.SetMomentum( momentum * (p/pp) );
88  }
89 
90  // calculate black track energies
91  tkin = targetNucleus.EvaporationEffects( ek );
92  ek -= tkin;
93  modifiedOriginal.SetKineticEnergy( ek*MeV );
94  et = ek + amas;
95  p = std::sqrt( std::abs((et-amas)*(et+amas)) );
96  pp = modifiedOriginal.GetMomentum().mag()/MeV;
97  if (pp > 0.0) {
98  G4ThreeVector momentum = modifiedOriginal.GetMomentum();
99  modifiedOriginal.SetMomentum( momentum * (p/pp) );
100  }
101  G4ReactionProduct currentParticle = modifiedOriginal;
102  G4ReactionProduct targetParticle;
103  targetParticle = *originalTarget;
104  currentParticle.SetSide(1); // incident always goes in forward hemisphere
105  targetParticle.SetSide(-1); // target always goes in backward hemisphere
106  G4bool incidentHasChanged = false;
107  G4bool targetHasChanged = false;
108  G4bool quasiElastic = false;
109  G4FastVector<G4ReactionProduct,GHADLISTSIZE> vec; // vec will contain the secondary particles
110  G4int vecLen = 0;
111  vec.Initialize(0);
112 
113  const G4double cutOff = 0.1;
114  const G4double anni = std::min( 1.3*currentParticle.GetTotalMomentum()/GeV, 0.4 );
115  if ((currentParticle.GetKineticEnergy()/MeV > cutOff) ||
116  (G4UniformRand() > anni) )
117  Cascade(vec, vecLen, originalIncident, currentParticle, targetParticle,
118  incidentHasChanged, targetHasChanged, quasiElastic);
119 
120  CalculateMomenta(vec, vecLen, originalIncident, originalTarget,
121  modifiedOriginal, targetNucleus, currentParticle,
122  targetParticle, incidentHasChanged, targetHasChanged,
123  quasiElastic);
124 
125  SetUpChange(vec, vecLen, currentParticle, targetParticle, incidentHasChanged);
126 
127  if (isotopeProduction) DoIsotopeCounting(originalIncident, targetNucleus);
128 
129  delete originalTarget;
130  return &theParticleChange;
131 }
132 
133 
134 void G4LEAntiXiZeroInelastic::Cascade(
136  G4int& vecLen,
137  const G4HadProjectile *originalIncident,
138  G4ReactionProduct &currentParticle,
139  G4ReactionProduct &targetParticle,
140  G4bool &incidentHasChanged,
141  G4bool &targetHasChanged,
142  G4bool &quasiElastic)
143 {
144  // derived from original FORTRAN code CASAX0 by H. Fesefeldt (20-Jan-1989)
145  // which is just a copy of CASX0 (cascade for Xi0)
146  //
147  // AntiXiZero undergoes interaction with nucleon within a nucleus. Check if it is
148  // energetically possible to produce pions/kaons. In not, assume nuclear excitation
149  // occurs and input particle is degraded in energy. No other particles are produced.
150  // If reaction is possible, find the correct number of pions/protons/neutrons
151  // produced using an interpolation to multiplicity data. Replace some pions or
152  // protons/neutrons by kaons or strange baryons according to the average
153  // multiplicity per inelastic reaction.
154  //
155  const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass()/MeV;
156  const G4double etOriginal = originalIncident->GetTotalEnergy()/MeV;
157  const G4double targetMass = targetParticle.GetMass()/MeV;
158  G4double centerofmassEnergy = std::sqrt( mOriginal*mOriginal +
159  targetMass*targetMass +
160  2.0*targetMass*etOriginal );
161  G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
162  if( availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass()/MeV )
163  {
164  quasiElastic = true;
165  return;
166  }
167  static G4bool first = true;
168  const G4int numMul = 1200;
169  const G4int numSec = 60;
170  static G4double protmul[numMul], protnorm[numSec]; // proton constants
171  static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
172  // npos = number of pi+, nneg = number of pi-, nzero = number of pi0
173  G4int counter, nt=0, npos=0, nneg=0, nzero=0;
174  G4double test;
175  const G4double c = 1.25;
176  const G4double b[] = { 0.7, 0.7 };
177  if( first ) // compute normalization constants, this will only be Done once
178  {
179  first = false;
180  G4int i;
181  for( i=0; i<numMul; ++i )protmul[i] = 0.0;
182  for( i=0; i<numSec; ++i )protnorm[i] = 0.0;
183  counter = -1;
184  for( npos=0; npos<(numSec/3); ++npos )
185  {
186  for( nneg=std::max(0,npos-2); nneg<=(npos+1); ++nneg )
187  {
188  for( nzero=0; nzero<numSec/3; ++nzero )
189  {
190  if( ++counter < numMul )
191  {
192  nt = npos+nneg+nzero;
193  if( nt>0 && nt<=numSec )
194  {
195  protmul[counter] = Pmltpc(npos,nneg,nzero,nt,b[0],c);
196  protnorm[nt-1] += protmul[counter];
197  }
198  }
199  }
200  }
201  }
202  for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
203  for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
204  counter = -1;
205  for( npos=0; npos<numSec/3; ++npos )
206  {
207  for( nneg=std::max(0,npos-1); nneg<=(npos+2); ++nneg )
208  {
209  for( nzero=0; nzero<numSec/3; ++nzero )
210  {
211  if( ++counter < numMul )
212  {
213  nt = npos+nneg+nzero;
214  if( nt>0 && nt<=numSec )
215  {
216  neutmul[counter] = Pmltpc(npos,nneg,nzero,nt,b[1],c);
217  neutnorm[nt-1] += neutmul[counter];
218  }
219  }
220  }
221  }
222  }
223  for( i=0; i<numSec; ++i )
224  {
225  if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
226  if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
227  }
228  } // end of initialization
229 
230  const G4double expxu = 82.; // upper bound for arg. of exp
231  const G4double expxl = -expxu; // lower bound for arg. of exp
237  //
238  // energetically possible to produce pion(s) --> inelastic scattering
239  //
240  G4double n, anpn;
241  GetNormalizationConstant( availableEnergy, n, anpn );
242  G4double ran = G4UniformRand();
243  G4double dum, excs = 0.0;
244  if( targetParticle.GetDefinition() == aProton )
245  {
246  counter = -1;
247  for( npos=0; npos<numSec/3 && ran>=excs; ++npos )
248  {
249  for( nneg=std::max(0,npos-2); nneg<=(npos+1) && ran>=excs; ++nneg )
250  {
251  for( nzero=0; nzero<numSec/3 && ran>=excs; ++nzero )
252  {
253  if( ++counter < numMul )
254  {
255  nt = npos+nneg+nzero;
256  if( nt>0 && nt<=numSec )
257  {
258  test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
259  dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
260  if( std::fabs(dum) < 1.0 )
261  {
262  if( test >= 1.0e-10 )excs += dum*test;
263  }
264  else
265  excs += dum*test;
266  }
267  }
268  }
269  }
270  }
271  if( ran >= excs ) // 3 previous loops continued to the end
272  {
273  quasiElastic = true;
274  return;
275  }
276  npos--; nneg--; nzero--;
277  //
278  // number of secondary mesons determined by kno distribution
279  // check for total charge of final state mesons to determine
280  // the kind of baryons to be produced, taking into account
281  // charge and strangeness conservation
282  //
283  if( npos < nneg+1 )
284  {
285  if( npos != nneg ) // charge mismatch
286  {
287  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
288  incidentHasChanged = true;
289  //
290  // correct the strangeness by replacing a pi- by a kaon-
291  //
292  vec.Initialize( 1 );
294  p->SetDefinition( aKaonMinus );
295  (G4UniformRand() < 0.5) ? p->SetSide( -1 ) : p->SetSide( 1 );
296  vec.SetElement( vecLen++, p );
297  --nneg;
298  }
299  }
300  else if( npos == nneg+1 )
301  {
302  if( G4UniformRand() < 0.5 )
303  {
304  targetParticle.SetDefinitionAndUpdateE( aNeutron );
305  targetHasChanged = true;
306  }
307  else
308  {
309  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
310  incidentHasChanged = true;
311  }
312  }
313  else
314  {
315  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
316  incidentHasChanged = true;
317  targetParticle.SetDefinitionAndUpdateE( aNeutron );
318  targetHasChanged = true;
319  }
320  }
321  else // target must be a neutron
322  {
323  counter = -1;
324  for( npos=0; npos<numSec/3 && ran>=excs; ++npos )
325  {
326  for( nneg=std::max(0,npos-1); nneg<=(npos+2) && ran>=excs; ++nneg )
327  {
328  for( nzero=0; nzero<numSec/3 && ran>=excs; ++nzero )
329  {
330  if( ++counter < numMul )
331  {
332  nt = npos+nneg+nzero;
333  if( nt>0 && nt<=numSec )
334  {
335  test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
336  dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
337  if( std::fabs(dum) < 1.0 )
338  {
339  if( test >= 1.0e-10 )excs += dum*test;
340  }
341  else
342  excs += dum*test;
343  }
344  }
345  }
346  }
347  }
348  if( ran >= excs ) // 3 previous loops continued to the end
349  {
350  quasiElastic = true;
351  return;
352  }
353  npos--; nneg--; nzero--;
354  if( npos < nneg )
355  {
356  if( npos+1 == nneg )
357  {
358  targetParticle.SetDefinitionAndUpdateE( aProton );
359  targetHasChanged = true;
360  }
361  else // charge mismatch
362  {
363  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
364  incidentHasChanged = true;
365  targetParticle.SetDefinitionAndUpdateE( aProton );
366  targetHasChanged = true;
367  //
368  // correct the strangeness by replacing a pi- by a kaon-
369  //
370  vec.Initialize( 1 );
372  p->SetDefinition( aKaonMinus );
373  (G4UniformRand() < 0.5) ? p->SetSide( -1 ) : p->SetSide( 1 );
374  vec.SetElement( vecLen++, p );
375  --nneg;
376  }
377  }
378  else if( npos == nneg )
379  {
380  if( G4UniformRand() >= 0.5 )
381  {
382  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
383  incidentHasChanged = true;
384  targetParticle.SetDefinitionAndUpdateE( aProton );
385  targetHasChanged = true;
386  }
387  }
388  else
389  {
390  currentParticle.SetDefinitionAndUpdateE( aXiMinus );
391  incidentHasChanged = true;
392  }
393  }
394  SetUpPions( npos, nneg, nzero, vec, vecLen );
395  return;
396 }
397 
398  /* end of file */
399