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G4RPGLambdaInelastic.cc
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25 //
26 // $Id$
27 //
28 
29 #include "G4RPGLambdaInelastic.hh"
30 #include "G4PhysicalConstants.hh"
31 #include "G4SystemOfUnits.hh"
32 #include "Randomize.hh"
33 
36  G4Nucleus &targetNucleus )
37 {
38  const G4HadProjectile *originalIncident = &aTrack;
39 
40  // create the target particle
41 
42  G4DynamicParticle *originalTarget = targetNucleus.ReturnTargetParticle();
43 
44  if( verboseLevel > 1 )
45  {
46  const G4Material *targetMaterial = aTrack.GetMaterial();
47  G4cout << "G4RPGLambdaInelastic::ApplyYourself called" << G4endl;
48  G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy()/MeV << "MeV, ";
49  G4cout << "target material = " << targetMaterial->GetName() << ", ";
50  G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
51  << G4endl;
52  }
53 
54  // Fermi motion and evaporation
55  // As of Geant3, the Fermi energy calculation had not been Done
56 
57  G4double ek = originalIncident->GetKineticEnergy()/MeV;
58  G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
59  G4ReactionProduct modifiedOriginal;
60  modifiedOriginal = *originalIncident;
61 
62  G4double tkin = targetNucleus.Cinema( ek );
63  ek += tkin;
64  modifiedOriginal.SetKineticEnergy( ek*MeV );
65  G4double et = ek + amas;
66  G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
67  G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
68  if( pp > 0.0 )
69  {
70  G4ThreeVector momentum = modifiedOriginal.GetMomentum();
71  modifiedOriginal.SetMomentum( momentum * (p/pp) );
72  }
73  //
74  // calculate black track energies
75  //
76  tkin = targetNucleus.EvaporationEffects( ek );
77  ek -= tkin;
78  modifiedOriginal.SetKineticEnergy( ek*MeV );
79  et = ek + amas;
80  p = std::sqrt( std::abs((et-amas)*(et+amas)) );
81  pp = modifiedOriginal.GetMomentum().mag()/MeV;
82  if( pp > 0.0 )
83  {
84  G4ThreeVector momentum = modifiedOriginal.GetMomentum();
85  modifiedOriginal.SetMomentum( momentum * (p/pp) );
86  }
87 
88  G4ReactionProduct currentParticle = modifiedOriginal;
89  G4ReactionProduct targetParticle;
90  targetParticle = *originalTarget;
91  currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
92  targetParticle.SetSide( -1 ); // target always goes in backward hemisphere
93  G4bool incidentHasChanged = false;
94  G4bool targetHasChanged = false;
95  G4bool quasiElastic = false;
96  G4FastVector<G4ReactionProduct,GHADLISTSIZE> vec; // vec will contain the secondary particles
97  G4int vecLen = 0;
98  vec.Initialize( 0 );
99 
100  const G4double cutOff = 0.1;
101  if( currentParticle.GetKineticEnergy()/MeV > cutOff )
102  Cascade( vec, vecLen,
103  originalIncident, currentParticle, targetParticle,
104  incidentHasChanged, targetHasChanged, quasiElastic );
105 
106  CalculateMomenta( vec, vecLen,
107  originalIncident, originalTarget, modifiedOriginal,
108  targetNucleus, currentParticle, targetParticle,
109  incidentHasChanged, targetHasChanged, quasiElastic );
110 
111  SetUpChange( vec, vecLen,
112  currentParticle, targetParticle,
113  incidentHasChanged );
114 
115  delete originalTarget;
116  return &theParticleChange;
117 }
118 
119 
120 void G4RPGLambdaInelastic::Cascade(
122  G4int& vecLen,
123  const G4HadProjectile *originalIncident,
124  G4ReactionProduct &currentParticle,
125  G4ReactionProduct &targetParticle,
126  G4bool &incidentHasChanged,
127  G4bool &targetHasChanged,
128  G4bool &quasiElastic )
129 {
130  // Derived from H. Fesefeldt's original FORTRAN code CASL0
131  //
132  // Lambda undergoes interaction with nucleon within a nucleus. Check if it is
133  // energetically possible to produce pions/kaons. In not, assume nuclear excitation
134  // occurs and input particle is degraded in energy. No other particles are produced.
135  // If reaction is possible, find the correct number of pions/protons/neutrons
136  // produced using an interpolation to multiplicity data. Replace some pions or
137  // protons/neutrons by kaons or strange baryons according to the average
138  // multiplicity per Inelastic reaction.
139 
140  const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass()/MeV;
141  const G4double etOriginal = originalIncident->GetTotalEnergy()/MeV;
142  const G4double targetMass = targetParticle.GetMass()/MeV;
143  G4double centerofmassEnergy = std::sqrt( mOriginal*mOriginal +
144  targetMass*targetMass +
145  2.0*targetMass*etOriginal );
146  G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
147  if( availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass()/MeV )
148  {
149  quasiElastic = true;
150  return;
151  }
152  static G4bool first = true;
153  const G4int numMul = 1200;
154  const G4int numSec = 60;
155  static G4double protmul[numMul], protnorm[numSec]; // proton constants
156  static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
157 
158  // np = number of pi+, nneg = number of pi-, nz = number of pi0
159 
160  G4int counter, nt=0, np=0, nneg=0, nz=0;
161  G4double test;
162  const G4double c = 1.25;
163  const G4double b[] = { 0.70, 0.35 };
164  if( first ) { // compute normalization constants, this will only be Done once
165  first = false;
166  G4int i;
167  for( i=0; i<numMul; ++i )protmul[i] = 0.0;
168  for( i=0; i<numSec; ++i )protnorm[i] = 0.0;
169  counter = -1;
170  for( np=0; np<(numSec/3); ++np ) {
171  for( nneg=std::max(0,np-2); nneg<=(np+1); ++nneg ) {
172  for( nz=0; nz<numSec/3; ++nz ) {
173  if( ++counter < numMul ) {
174  nt = np+nneg+nz;
175  if( nt>0 && nt<=numSec ) {
176  protmul[counter] = Pmltpc(np,nneg,nz,nt,b[0],c);
177  protnorm[nt-1] += protmul[counter];
178  }
179  }
180  }
181  }
182  }
183  for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
184  for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
185  counter = -1;
186  for( np=0; np<numSec/3; ++np ) {
187  for( nneg=std::max(0,np-1); nneg<=(np+2); ++nneg ) {
188  for( nz=0; nz<numSec/3; ++nz ) {
189  if( ++counter < numMul ) {
190  nt = np+nneg+nz;
191  if( nt>0 && nt<=numSec ) {
192  neutmul[counter] = Pmltpc(np,nneg,nz,nt,b[1],c);
193  neutnorm[nt-1] += neutmul[counter];
194  }
195  }
196  }
197  }
198  }
199  for( i=0; i<numSec; ++i ) {
200  if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
201  if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
202  }
203  } // end of initialization
204 
205  const G4double expxu = 82.; // upper bound for arg. of exp
206  const G4double expxl = -expxu; // lower bound for arg. of exp
212 
213  // energetically possible to produce pion(s) --> inelastic scattering
214  // otherwise quasi-elastic scattering
215 
216  G4double n, anpn;
217  GetNormalizationConstant( availableEnergy, n, anpn );
218  G4double ran = G4UniformRand();
219  G4double dum, excs = 0.0;
220  if( targetParticle.GetDefinition() == aProton ) {
221  counter = -1;
222  for( np=0; np<numSec/3 && ran>=excs; ++np ) {
223  for( nneg=std::max(0,np-2); nneg<=(np+1) && ran>=excs; ++nneg ) {
224  for( nz=0; nz<numSec/3 && ran>=excs; ++nz ) {
225  if( ++counter < numMul ) {
226  nt = np+nneg+nz;
227  if( nt>0 && nt<=numSec ) {
228  test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
229  dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
230  if( std::fabs(dum) < 1.0 ) {
231  if( test >= 1.0e-10 )excs += dum*test;
232  } else {
233  excs += dum*test;
234  }
235  }
236  }
237  }
238  }
239  }
240  if( ran >= excs ) // 3 previous loops continued to the end
241  {
242  quasiElastic = true;
243  return;
244  }
245  np--; nneg--; nz--;
246  G4int ncht = std::max( 1, np-nneg );
247  switch( ncht ) {
248  case 1:
249  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
250  incidentHasChanged = true;
251  break;
252  case 2:
253  if( G4UniformRand() < 0.5 ) {
254  if( G4UniformRand() < 0.5 ) {
255  currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
256  incidentHasChanged = true;
257  }
258  } else {
259  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
260  incidentHasChanged = true;
261  targetParticle.SetDefinitionAndUpdateE( aNeutron );
262  targetHasChanged = true;
263  }
264  break;
265  case 3:
266  if( G4UniformRand() < 0.5 ) {
267  if( G4UniformRand() < 0.5 ) {
268  currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
269  incidentHasChanged = true;
270  }
271  targetParticle.SetDefinitionAndUpdateE( aNeutron );
272  targetHasChanged = true;
273  } else {
274  currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
275  incidentHasChanged = true;
276  }
277  break;
278  default:
279  currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
280  incidentHasChanged = true;
281  targetParticle.SetDefinitionAndUpdateE( aNeutron );
282  targetHasChanged = true;
283  break;
284  }
285  }
286  else // target must be a neutron
287  {
288  counter = -1;
289  for( np=0; np<numSec/3 && ran>=excs; ++np ) {
290  for( nneg=std::max(0,np-1); nneg<=(np+2) && ran>=excs; ++nneg ) {
291  for( nz=0; nz<numSec/3 && ran>=excs; ++nz ) {
292  if( ++counter < numMul ) {
293  nt = np+nneg+nz;
294  if( nt>0 && nt<=numSec ) {
295  test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
296  dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
297  if( std::fabs(dum) < 1.0 ) {
298  if( test >= 1.0e-10 )excs += dum*test;
299  } else {
300  excs += dum*test;
301  }
302  }
303  }
304  }
305  }
306  }
307  if( ran >= excs ) // 3 previous loops continued to the end
308  {
309  quasiElastic = true;
310  return;
311  }
312  np--; nneg--; nz--;
313  G4int ncht = std::max( 1, np-nneg+3 );
314  switch( ncht ) {
315  case 1:
316  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
317  incidentHasChanged = true;
318  targetParticle.SetDefinitionAndUpdateE( aProton );
319  targetHasChanged = true;
320  break;
321  case 2:
322  if( G4UniformRand() < 0.5 ) {
323  if( G4UniformRand() < 0.5 ) {
324  currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
325  incidentHasChanged = true;
326  }
327  targetParticle.SetDefinitionAndUpdateE( aProton );
328  targetHasChanged = true;
329  } else {
330  currentParticle.SetDefinitionAndUpdateE( aSigmaPlus );
331  incidentHasChanged = true;
332  }
333  break;
334  case 3:
335  if( G4UniformRand() < 0.5 ) {
336  if( G4UniformRand() < 0.5 ) {
337  currentParticle.SetDefinitionAndUpdateE( aSigmaZero );
338  incidentHasChanged = true;
339  }
340  } else {
341  currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
342  incidentHasChanged = true;
343  targetParticle.SetDefinitionAndUpdateE( aProton );
344  targetHasChanged = true;
345  }
346  break;
347  default:
348  currentParticle.SetDefinitionAndUpdateE( aSigmaMinus );
349  incidentHasChanged = true;
350  break;
351  }
352  }
353 
354  SetUpPions(np, nneg, nz, vec, vecLen);
355  return;
356 }
357 
358  /* end of file */
359