source: trunk/source/processes/hadronic/models/low_energy/src/G4LEPionMinusInelastic.cc@ 1036

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27//
28 // Hadronic Process: PionMinus Inelastic Process
29 // J.L. Chuma, TRIUMF, 19-Nov-1996
30 // Last modified: 27-Mar-1997
31 // Modified by J.L.Chuma 30-Apr-97: added originalTarget for CalculateMomenta
32
33#include "G4LEPionMinusInelastic.hh"
34#include "Randomize.hh"
35
36 G4HadFinalState *
37 G4LEPionMinusInelastic::ApplyYourself( const G4HadProjectile &aTrack,
38 G4Nucleus &targetNucleus )
39 {
40 const G4HadProjectile *originalIncident = &aTrack;
41 if (originalIncident->GetKineticEnergy()<= 0.1*MeV)
42 {
43 theParticleChange.SetStatusChange(isAlive);
44 theParticleChange.SetEnergyChange(aTrack.GetKineticEnergy());
45 theParticleChange.SetMomentumChange(aTrack.Get4Momentum().vect().unit());
46 return &theParticleChange;
47 }
48
49 // create the target particle
50
51 G4DynamicParticle *originalTarget = targetNucleus.ReturnTargetParticle();
52// G4double targetMass = originalTarget->GetDefinition()->GetPDGMass();
53 G4ReactionProduct targetParticle( originalTarget->GetDefinition() );
54
55 if( verboseLevel > 1 )
56 {
57 const G4Material *targetMaterial = aTrack.GetMaterial();
58 G4cout << "G4PionMinusInelastic::ApplyYourself called" << G4endl;
59 G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy() << "MeV, ";
60 G4cout << "target material = " << targetMaterial->GetName() << ", ";
61 G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
62 << G4endl;
63 }
64 G4ReactionProduct currentParticle(
65 const_cast<G4ParticleDefinition *>(originalIncident->GetDefinition() ) );
66 currentParticle.SetMomentum( originalIncident->Get4Momentum().vect() );
67 currentParticle.SetKineticEnergy( originalIncident->GetKineticEnergy() );
68
69 // Fermi motion and evaporation
70 // As of Geant3, the Fermi energy calculation had not been Done
71
72 G4double ek = originalIncident->GetKineticEnergy();
73 G4double amas = originalIncident->GetDefinition()->GetPDGMass();
74
75 G4double tkin = targetNucleus.Cinema( ek );
76 ek += tkin;
77 currentParticle.SetKineticEnergy( ek );
78 G4double et = ek + amas;
79 G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
80 G4double pp = currentParticle.GetMomentum().mag();
81 if( pp > 0.0 )
82 {
83 G4ThreeVector momentum = currentParticle.GetMomentum();
84 currentParticle.SetMomentum( momentum * (p/pp) );
85 }
86
87 // calculate black track energies
88
89 tkin = targetNucleus.EvaporationEffects( ek );
90 ek -= tkin;
91 currentParticle.SetKineticEnergy( ek );
92 et = ek + amas;
93 p = std::sqrt( std::abs((et-amas)*(et+amas)) );
94 pp = currentParticle.GetMomentum().mag();
95 if( pp > 0.0 )
96 {
97 G4ThreeVector momentum = currentParticle.GetMomentum();
98 currentParticle.SetMomentum( momentum * (p/pp) );
99 }
100
101 G4ReactionProduct modifiedOriginal = currentParticle;
102
103 currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
104 targetParticle.SetSide( -1 ); // target always goes in backward hemisphere
105 G4bool incidentHasChanged = false;
106 G4bool targetHasChanged = false;
107 G4bool quasiElastic = false;
108 G4FastVector<G4ReactionProduct,GHADLISTSIZE> vec; // vec will contain the secondary particles
109 G4int vecLen = 0;
110 vec.Initialize( 0 );
111
112 const G4double cutOff = 0.1*MeV;
113 if( currentParticle.GetKineticEnergy() > cutOff )
114 Cascade( vec, vecLen,
115 originalIncident, currentParticle, targetParticle,
116 incidentHasChanged, targetHasChanged, quasiElastic );
117
118 CalculateMomenta( vec, vecLen,
119 originalIncident, originalTarget, modifiedOriginal,
120 targetNucleus, currentParticle, targetParticle,
121 incidentHasChanged, targetHasChanged, quasiElastic );
122
123 SetUpChange( vec, vecLen,
124 currentParticle, targetParticle,
125 incidentHasChanged );
126
127 delete originalTarget;
128 return &theParticleChange;
129 }
130
131 void
132 G4LEPionMinusInelastic::Cascade(
133 G4FastVector<G4ReactionProduct,GHADLISTSIZE> &vec,
134 G4int& vecLen,
135 const G4HadProjectile *originalIncident,
136 G4ReactionProduct &currentParticle,
137 G4ReactionProduct &targetParticle,
138 G4bool &incidentHasChanged,
139 G4bool &targetHasChanged,
140 G4bool &quasiElastic )
141 {
142 // derived from original FORTRAN code CASPIM by H. Fesefeldt (13-Sep-1987)
143 //
144 // pi- undergoes interaction with nucleon within nucleus.
145 // Check if energetically possible to produce pions/kaons.
146 // If not assume nuclear excitation occurs and input particle
147 // is degraded in energy. No other particles produced.
148 // If reaction is possible find correct number of pions/protons/neutrons
149 // produced using an interpolation to multiplicity data.
150 // Replace some pions or protons/neutrons by kaons or strange baryons
151 // according to average multiplicity per inelastic reactions.
152 //
153 const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass();
154 const G4double etOriginal = originalIncident->GetTotalEnergy();
155 const G4double pOriginal = originalIncident->GetTotalMomentum();
156 const G4double targetMass = targetParticle.GetMass();
157 G4double centerofmassEnergy = std::sqrt( mOriginal*mOriginal +
158 targetMass*targetMass +
159 2.0*targetMass*etOriginal );
160 G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
161 static G4bool first = true;
162 const G4int numMul = 1200;
163 const G4int numSec = 60;
164 static G4double protmul[numMul], protnorm[numSec]; // proton constants
165 static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
166 // np = number of pi+, nm = number of pi-, nz = number of pi0
167 G4int counter, nt=0, np=0, nm=0, nz=0;
168 const G4double c = 1.25;
169 const G4double b[] = { 0.70, 0.70 };
170 if( first ) // compute normalization constants, this will only be Done once
171 {
172 first = false;
173 G4int i;
174 for( i=0; i<numMul; ++i )protmul[i] = 0.0;
175 for( i=0; i<numSec; ++i )protnorm[i] = 0.0;
176 counter = -1;
177 for( np=0; np<(numSec/3); ++np )
178 {
179 for( nm=std::max(0,np-1); nm<=(np+1); ++nm )
180 {
181 for( nz=0; nz<numSec/3; ++nz )
182 {
183 if( ++counter < numMul )
184 {
185 nt = np+nm+nz;
186 if( nt > 0 )
187 {
188 protmul[counter] = Pmltpc(np,nm,nz,nt,b[0],c);
189 protnorm[nt-1] += protmul[counter];
190 }
191 }
192 }
193 }
194 }
195 for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
196 for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
197 counter = -1;
198 for( np=0; np<numSec/3; ++np )
199 {
200 for( nm=np; nm<=(np+2); ++nm )
201 {
202 for( nz=0; nz<numSec/3; ++nz )
203 {
204 if( ++counter < numMul )
205 {
206 nt = np+nm+nz;
207 if( (nt>0) && (nt<=numSec) )
208 {
209 neutmul[counter] = Pmltpc(np,nm,nz,nt,b[1],c);
210 neutnorm[nt-1] += neutmul[counter];
211 }
212 }
213 }
214 }
215 }
216 for( i=0; i<numSec; ++i )
217 {
218 if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
219 if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
220 }
221 } // end of initialization
222
223 const G4double expxu = 82.; // upper bound for arg. of exp
224 const G4double expxl = -expxu; // lower bound for arg. of exp
225 G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
226 G4ParticleDefinition *aProton = G4Proton::Proton();
227 G4ParticleDefinition *aPiZero = G4PionZero::PionZero();
228 G4int ieab = G4int(availableEnergy*5.0/GeV);
229 const G4double supp[] = {0.,0.4,0.55,0.65,0.75,0.82,0.86,0.90,0.94,0.98};
230 G4double test, w0, wp, wt, wm;
231 if( (availableEnergy<2.0*GeV) && (G4UniformRand()>=supp[ieab]) )
232 {
233 // suppress high multiplicity events at low momentum
234 // only one pion will be produced
235
236 // charge exchange reaction is included in inelastic cross section
237
238 const G4double cech[] = {1.,0.95,0.79,0.32,0.19,0.16,0.14,0.12,0.10,0.08};
239 G4int iplab = G4int(std::min( 9.0, pOriginal/GeV*5.0 ));
240 if( G4UniformRand() <= cech[iplab] )
241 {
242 if( targetParticle.GetDefinition() == aProton )
243 {
244 currentParticle.SetDefinitionAndUpdateE( aPiZero ); // charge exchange
245 targetParticle.SetDefinitionAndUpdateE( aNeutron );
246 incidentHasChanged = true;
247 targetHasChanged = true;
248 }
249 }
250
251 if( availableEnergy <= G4PionMinus::PionMinus()->GetPDGMass() )
252 {
253 quasiElastic = true;
254 return;
255 }
256
257 nm = np = nz = 0;
258 if( targetParticle.GetDefinition() == aProton )
259 {
260 test = std::exp( std::min( expxu, std::max( expxl, -(1.0+b[0])*(1.0+b[0])/(2.0*c*c) ) ) );
261 w0 = test;
262 wp = 10.0*test;
263 test = std::exp( std::min( expxu, std::max( expxl, -(-1.0+b[0])*(-1.0+b[0])/(2.0*c*c) ) ) );
264 wm = test;
265 wt = w0+wp+wm;
266 wp += w0;
267 G4double ran = G4UniformRand();
268 if( ran < w0/wt )
269 nz = 1;
270 else if( ran < wp/wt )
271 np = 1;
272 else
273 nm = 1;
274 }
275 else // target is a neutron
276 {
277 test = std::exp( std::min( expxu, std::max( expxl, -(1.0+b[1])*(1.0+b[1])/(2.0*c*c) ) ) );
278 w0 = test;
279 test = std::exp( std::min( expxu, std::max( expxl, -(-1.0+b[1])*(-1.0+b[1])/(2.0*c*c) ) ) );
280 wm = test;
281 G4double ran = G4UniformRand();
282 if( ran < w0/(w0+wm) )
283 nz = 1;
284 else
285 nm = 1;
286 }
287 }
288 else
289 {
290 if( availableEnergy <= G4PionMinus::PionMinus()->GetPDGMass() )
291 {
292 quasiElastic = true;
293 return;
294 }
295 G4double n, anpn;
296 GetNormalizationConstant( availableEnergy, n, anpn );
297 G4double ran = G4UniformRand();
298 G4double dum, excs = 0.0;
299 if( targetParticle.GetDefinition() == aProton )
300 {
301 counter = -1;
302 for( np=0; (np<numSec/3) && (ran>=excs); ++np )
303 {
304 for( nm=std::max(0,np-1); (nm<=(np+1)) && (ran>=excs); ++nm )
305 {
306 for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz )
307 {
308 if( ++counter < numMul )
309 {
310 nt = np+nm+nz;
311 if( nt > 0 )
312 {
313 test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
314 dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
315 if( std::fabs(dum) < 1.0 )
316 {
317 if( test >= 1.0e-10 )excs += dum*test;
318 }
319 else
320 excs += dum*test;
321 }
322 }
323 }
324 }
325 }
326 if( ran >= excs ) // 3 previous loops continued to the end
327 {
328 quasiElastic = true;
329 return;
330 }
331 np--; nm--; nz--;
332 }
333 else // target must be a neutron
334 {
335 counter = -1;
336 for( np=0; (np<numSec/3) && (ran>=excs); ++np )
337 {
338 for( nm=np; (nm<=(np+2)) && (ran>=excs); ++nm )
339 {
340 for( nz=0; (nz<numSec/3) && (ran>=excs); ++nz )
341 {
342 if( ++counter < numMul )
343 {
344 nt = np+nm+nz;
345 if( (nt>=1) && (nt<=numSec) )
346 {
347 test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
348 dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
349 if( std::fabs(dum) < 1.0 )
350 {
351 if( test >= 1.0e-10 )excs += dum*test;
352 }
353 else
354 excs += dum*test;
355 }
356 }
357 }
358 }
359 }
360 if( ran >= excs ) // 3 previous loops continued to the end
361 {
362 quasiElastic = true;
363 return;
364 }
365 np--; nm--; nz--;
366 }
367 }
368 if( targetParticle.GetDefinition() == aProton )
369 {
370 switch( np-nm )
371 {
372 case 0:
373 if( G4UniformRand() >= 0.75 )
374 {
375 currentParticle.SetDefinitionAndUpdateE( aPiZero );
376 targetParticle.SetDefinitionAndUpdateE( aNeutron );
377 incidentHasChanged = true;
378 targetHasChanged = true;
379 }
380 break;
381 case 1:
382 targetParticle.SetDefinitionAndUpdateE( aNeutron );
383 targetHasChanged = true;
384 break;
385 default:
386 currentParticle.SetDefinitionAndUpdateE( aPiZero );
387 incidentHasChanged = true;
388 break;
389 }
390 }
391 else
392 {
393 switch( np-nm )
394 {
395 case -1:
396 if( G4UniformRand() < 0.5 )
397 {
398 targetParticle.SetDefinitionAndUpdateE( aProton );
399 targetHasChanged = true;
400 } else {
401 currentParticle.SetDefinitionAndUpdateE( aPiZero );
402 incidentHasChanged = true;
403 }
404 break;
405 case 0:
406 break;
407 default:
408 currentParticle.SetDefinitionAndUpdateE( aPiZero );
409 incidentHasChanged = true;
410 break;
411 }
412 }
413 SetUpPions( np, nm, nz, vec, vecLen );
414 return;
415 }
416
417 /* end of file */
418
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