source: trunk/source/processes/hadronic/models/parton_string/qgsm/src/G4QGSDiffractiveExcitation.cc@ 1036

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27// $Id: G4QGSDiffractiveExcitation.cc,v 1.1 2007/05/25 07:30:47 gunter Exp $
28// ------------------------------------------------------------
29// GEANT 4 class implemetation file
30//
31// ---------------- G4QGSDiffractiveExcitation --------------
32// by Gunter Folger, October 1998.
33// diffractive Excitation used by strings models
34// Take a projectile and a target
35// excite the projectile and target
36// Essential changed by V. Uzhinsky in November - December 2006
37// in order to put it in a correspondence with original FRITIOF
38// model. Variant of FRITIOF with nucleon de-excitation is implemented.
39// ---------------------------------------------------------------------
40
41// Modified:
42// 25-05-07 : G.Folger
43// move from management/G4DiffractiveExcitation to to qgsm/G4QGSDiffractiveExcitation
44//
45
46#include "globals.hh"
47#include "Randomize.hh"
48
49#include "G4QGSDiffractiveExcitation.hh"
50#include "G4LorentzRotation.hh"
51#include "G4ThreeVector.hh"
52#include "G4ParticleDefinition.hh"
53#include "G4VSplitableHadron.hh"
54#include "G4ExcitedString.hh"
55//#include "G4ios.hh"
56
57G4QGSDiffractiveExcitation::G4QGSDiffractiveExcitation() // Uzhi
58{
59}
60
61G4bool G4QGSDiffractiveExcitation::
62 ExciteParticipants(G4VSplitableHadron *projectile, G4VSplitableHadron *target) const
63{
64
65 G4LorentzVector Pprojectile=projectile->Get4Momentum();
66
67// -------------------- Projectile parameters -----------------------------------
68 G4bool PutOnMassShell=0;
69
70// G4double M0projectile=projectile->GetDefinition()->GetPDGMass(); // With de-excitation
71 G4double M0projectile = Pprojectile.mag(); // Without de-excitation
72
73 if(M0projectile < projectile->GetDefinition()->GetPDGMass())
74 {
75 PutOnMassShell=1;
76 M0projectile=projectile->GetDefinition()->GetPDGMass();
77 }
78
79 G4double Mprojectile2 = M0projectile * M0projectile;
80
81 G4int PDGcode=projectile->GetDefinition()->GetPDGEncoding();
82 G4int absPDGcode=std::abs(PDGcode);
83 G4double ProjectileDiffCut;
84 G4double AveragePt2;
85
86 if( absPDGcode > 1000 ) //------Projectile is baryon --------
87 {
88 ProjectileDiffCut = 1.1; // GeV
89 AveragePt2 = 0.3; // GeV^2
90 }
91 else if( absPDGcode == 211 || PDGcode == 111) //------Projectile is Pion -----------
92 {
93 ProjectileDiffCut = 1.0; // GeV
94 AveragePt2 = 0.3; // GeV^2
95 }
96 else if( absPDGcode == 321 || PDGcode == -311) //------Projectile is Kaon -----------
97 {
98 ProjectileDiffCut = 1.1; // GeV
99 AveragePt2 = 0.3; // GeV^2
100 }
101 else //------Projectile is undefined, Nucleon assumed
102 {
103 ProjectileDiffCut = 1.1; // GeV
104 AveragePt2 = 0.3; // GeV^2
105 };
106
107 ProjectileDiffCut = ProjectileDiffCut * GeV;
108 AveragePt2 = AveragePt2 * GeV*GeV;
109
110// -------------------- Target parameters ----------------------------------------------
111 G4LorentzVector Ptarget=target->Get4Momentum();
112
113 G4double M0target = Ptarget.mag();
114
115 if(M0target < target->GetDefinition()->GetPDGMass())
116 {
117 PutOnMassShell=1;
118 M0target=target->GetDefinition()->GetPDGMass();
119 }
120
121 G4double Mtarget2 = M0target * M0target; //Ptarget.mag2(); // for AA-inter.
122
123 G4double NuclearNucleonDiffCut = 1.1*GeV;
124
125 G4double ProjectileDiffCut2 = ProjectileDiffCut * ProjectileDiffCut;
126 G4double NuclearNucleonDiffCut2 = NuclearNucleonDiffCut * NuclearNucleonDiffCut;
127
128// Transform momenta to cms and then rotate parallel to z axis;
129
130 G4LorentzVector Psum;
131 Psum=Pprojectile+Ptarget;
132
133 G4LorentzRotation toCms(-1*Psum.boostVector());
134
135 G4LorentzVector Ptmp=toCms*Pprojectile;
136
137 if ( Ptmp.pz() <= 0. )
138 {
139 // "String" moving backwards in CMS, abort collision !!
140 //G4cout << " abort Collision!! " << G4endl;
141 return false;
142 }
143
144 toCms.rotateZ(-1*Ptmp.phi());
145 toCms.rotateY(-1*Ptmp.theta());
146
147 G4LorentzRotation toLab(toCms.inverse());
148
149 Pprojectile.transform(toCms);
150 Ptarget.transform(toCms);
151
152 G4double Pt2;
153 G4double ProjMassT2, ProjMassT;
154 G4double TargMassT2, TargMassT;
155 G4double PZcms2, PZcms;
156 G4double PMinusNew, TPlusNew;
157
158 G4double S=Psum.mag2();
159 G4double SqrtS=std::sqrt(S);
160
161 if(SqrtS < 2200*MeV) {return false;} // The model cannot work for pp-interactions
162 // at Plab < 1.3 GeV/c. Uzhi
163
164 PZcms2=(S*S+Mprojectile2*Mprojectile2+Mtarget2*Mtarget2-
165 2*S*Mprojectile2-2*S*Mtarget2-2*Mprojectile2*Mtarget2)/4./S;
166 if(PZcms2 < 0)
167 {return false;} // It can be in an interaction with off-shell nuclear nucleon
168
169 PZcms = std::sqrt(PZcms2);
170
171 if(PutOnMassShell)
172 {
173 if(Pprojectile.z() > 0.)
174 {
175 Pprojectile.setPz( PZcms);
176 Ptarget.setPz( -PZcms);
177 }
178 else
179 {
180 Pprojectile.setPz(-PZcms);
181 Ptarget.setPz( PZcms);
182 };
183
184 Pprojectile.setE(std::sqrt(Mprojectile2+
185 Pprojectile.x()*Pprojectile.x()+
186 Pprojectile.y()*Pprojectile.y()+
187 PZcms2));
188 Ptarget.setE(std::sqrt( Mtarget2 +
189 Ptarget.x()*Ptarget.x()+
190 Ptarget.y()*Ptarget.y()+
191 PZcms2));
192 }
193
194 G4double maxPtSquare = PZcms2;
195
196//G4cout << "Pprojectile aft boost : " << Pprojectile << G4endl;
197//G4cout << "Ptarget aft boost : " << Ptarget << G4endl;
198// G4cout << "cms aft boost : " << (Pprojectile+ Ptarget) << G4endl;
199
200// G4cout << " Projectile Xplus / Xminus : " <<
201// Pprojectile.plus() << " / " << Pprojectile.minus() << G4endl;
202// G4cout << " Target Xplus / Xminus : " <<
203// Ptarget.plus() << " / " << Ptarget.minus() << G4endl;
204
205 G4LorentzVector Qmomentum;
206 G4double Qminus, Qplus;
207
208// /* Vova
209 G4int whilecount=0;
210 do {
211// Generate pt
212
213 if (whilecount++ >= 500 && (whilecount%100)==0)
214// G4cout << "G4QGSDiffractiveExcitation::ExciteParticipants possibly looping"
215// << ", loop count/ maxPtSquare : "
216// << whilecount << " / " << maxPtSquare << G4endl;
217 if (whilecount > 1000 )
218 {
219 Qmomentum=G4LorentzVector(0.,0.,0.,0.);
220 return false; // Ignore this interaction
221 }
222
223 Qmomentum=G4LorentzVector(GaussianPt(AveragePt2,maxPtSquare),0);
224
225//G4cout << "generated Pt " << Qmomentum << G4endl;
226//G4cout << "Pprojectile with pt : " << Pprojectile+Qmomentum << G4endl;
227//G4cout << "Ptarget with pt : " << Ptarget-Qmomentum << G4endl;
228
229// Momentum transfer
230/* // Uzhi
231 G4double Xmin = minmass / ( Pprojectile.e() + Ptarget.e() );
232 G4double Xmax=1.;
233 G4double Xplus =ChooseX(Xmin,Xmax);
234 G4double Xminus=ChooseX(Xmin,Xmax);
235
236// G4cout << " X-plus " << Xplus << G4endl;
237// G4cout << " X-minus " << Xminus << G4endl;
238
239 G4double pt2=G4ThreeVector(Qmomentum.vect()).mag2();
240 G4double Qplus =-1 * pt2 / Xminus/Ptarget.minus();
241 G4double Qminus= pt2 / Xplus /Pprojectile.plus();
242*/ // Uzhi *
243
244 Pt2=G4ThreeVector(Qmomentum.vect()).mag2();
245 ProjMassT2=Mprojectile2+Pt2;
246 ProjMassT =std::sqrt(ProjMassT2);
247
248 TargMassT2=Mtarget2+Pt2;
249 TargMassT =std::sqrt(TargMassT2);
250
251 PZcms2=(S*S+ProjMassT2*ProjMassT2+
252 TargMassT2*TargMassT2-
253 2.*S*ProjMassT2-2.*S*TargMassT2-
254 2.*ProjMassT2*TargMassT2)/4./S;
255 if(PZcms2 < 0 ) {PZcms2=0;};
256 PZcms =std::sqrt(PZcms2);
257
258 G4double PMinusMin=std::sqrt(ProjMassT2+PZcms2)-PZcms;
259 G4double PMinusMax=SqrtS-TargMassT;
260
261 PMinusNew=ChooseP(PMinusMin,PMinusMax);
262 Qminus=PMinusNew-Pprojectile.minus();
263
264 G4double TPlusMin=std::sqrt(TargMassT2+PZcms2)-PZcms;
265 G4double TPlusMax=SqrtS-ProjMassT;
266
267 TPlusNew=ChooseP(TPlusMin, TPlusMax);
268 Qplus=-(TPlusNew-Ptarget.plus());
269
270 Qmomentum.setPz( (Qplus-Qminus)/2 );
271 Qmomentum.setE( (Qplus+Qminus)/2 );
272
273//G4cout << "Qplus / Qminus " << Qplus << " / " << Qminus<<G4endl;
274// G4cout << "pt2" << pt2 << G4endl;
275// G4cout << "Qmomentum " << Qmomentum << G4endl;
276// G4cout << " Masses (P/T) : " << (Pprojectile+Qmomentum).mag() <<
277// " / " << (Ptarget-Qmomentum).mag() << G4endl;
278/* // Uzhi
279 } while ( (Pprojectile+Qmomentum).mag2() <= Mprojectile2 ||
280 (Ptarget-Qmomentum).mag2() <= Mtarget2 );
281*/ // Uzhi *
282
283
284 } while (( (Pprojectile+Qmomentum).mag2() < Mprojectile2 || // Uzhi No without excitation
285 (Ptarget -Qmomentum).mag2() < Mtarget2 ) || // Uzhi
286 ( (Pprojectile+Qmomentum).mag2() < ProjectileDiffCut2 && // Uzhi No double Diffraction
287 (Ptarget -Qmomentum).mag2() < NuclearNucleonDiffCut2) );// Uzhi
288
289 if((Ptarget-Qmomentum).mag2() < NuclearNucleonDiffCut2) // Uzhi Projectile diffraction
290 {
291 G4double TMinusNew=SqrtS-PMinusNew;
292 Qminus=Ptarget.minus()-TMinusNew;
293 TPlusNew=TargMassT2/TMinusNew;
294 Qplus=Ptarget.plus()-TPlusNew;
295
296 Qmomentum.setPz( (Qplus-Qminus)/2 );
297 Qmomentum.setE( (Qplus+Qminus)/2 );
298 }
299 else if((Pprojectile+Qmomentum).mag2() < ProjectileDiffCut2) // Uzhi Target diffraction
300 {
301 G4double PPlusNew=SqrtS-TPlusNew;
302 Qplus=PPlusNew-Pprojectile.plus();
303 PMinusNew=ProjMassT2/PPlusNew;
304 Qminus=PMinusNew-Pprojectile.minus();
305
306 Qmomentum.setPz( (Qplus-Qminus)/2 );
307 Qmomentum.setE( (Qplus+Qminus)/2 );
308 };
309
310 Pprojectile += Qmomentum;
311 Ptarget -= Qmomentum;
312
313 // Vova
314
315/*
316Pprojectile.setPz(0.);
317Pprojectile.setE(SqrtS-M0target);
318
319Ptarget.setPz(0.);
320Ptarget.setE(M0target);
321*/
322
323//G4cout << "Pprojectile with Q : " << Pprojectile << G4endl;
324//G4cout << "Ptarget with Q : " << Ptarget << G4endl;
325
326// G4cout << "Projectile back: " << toLab * Pprojectile << G4endl;
327// G4cout << "Target back: " << toLab * Ptarget << G4endl;
328
329// Transform back and update SplitableHadron Participant.
330 Pprojectile.transform(toLab);
331 Ptarget.transform(toLab);
332
333//G4cout << "Pprojectile with Q M: " << Pprojectile<<" "<< Pprojectile.mag() << G4endl;
334//G4cout << "Ptarget with Q M: " << Ptarget <<" "<< Ptarget.mag() << G4endl;
335
336//G4cout << "Target mass " << Ptarget.mag() << G4endl;
337
338 target->Set4Momentum(Ptarget);
339
340//G4cout << "Projectile mass " << Pprojectile.mag() << G4endl;
341
342 projectile->Set4Momentum(Pprojectile);
343
344 return true;
345}
346
347
348G4ExcitedString * G4QGSDiffractiveExcitation::
349 String(G4VSplitableHadron * hadron, G4bool isProjectile) const
350{
351 hadron->SplitUp();
352 G4Parton *start= hadron->GetNextParton();
353 if ( start==NULL)
354 { G4cout << " G4FTFModel::String() Error:No start parton found"<< G4endl;
355 return NULL;
356 }
357 G4Parton *end = hadron->GetNextParton();
358 if ( end==NULL)
359 { G4cout << " G4FTFModel::String() Error:No end parton found"<< G4endl;
360 return NULL;
361 }
362
363 G4ExcitedString * string;
364 if ( isProjectile )
365 {
366 string= new G4ExcitedString(end,start, +1);
367 } else {
368 string= new G4ExcitedString(start,end, -1);
369 }
370
371 string->SetPosition(hadron->GetPosition());
372
373// momenta of string ends
374 G4double ptSquared= hadron->Get4Momentum().perp2();
375 G4double transverseMassSquared= hadron->Get4Momentum().plus()
376 * hadron->Get4Momentum().minus();
377
378
379 G4double maxAvailMomentumSquared=
380 sqr( std::sqrt(transverseMassSquared) - std::sqrt(ptSquared) );
381
382 G4double widthOfPtSquare = 0.25; // Uzhi <Pt^2>=0.25 ??????????????????
383 G4ThreeVector pt=GaussianPt(widthOfPtSquare,maxAvailMomentumSquared);
384
385 G4LorentzVector Pstart(G4LorentzVector(pt,0.));
386 G4LorentzVector Pend;
387 Pend.setPx(hadron->Get4Momentum().px() - pt.x());
388 Pend.setPy(hadron->Get4Momentum().py() - pt.y());
389
390 G4double tm1=hadron->Get4Momentum().minus() +
391 ( Pend.perp2()-Pstart.perp2() ) / hadron->Get4Momentum().plus();
392
393 G4double tm2= std::sqrt( std::max(0., sqr(tm1) -
394 4. * Pend.perp2() * hadron->Get4Momentum().minus()
395 / hadron->Get4Momentum().plus() ));
396
397 G4int Sign= isProjectile ? -1 : 1;
398
399 G4double endMinus = 0.5 * (tm1 + Sign*tm2);
400 G4double startMinus= hadron->Get4Momentum().minus() - endMinus;
401
402 G4double startPlus= Pstart.perp2() / startMinus;
403 G4double endPlus = hadron->Get4Momentum().plus() - startPlus;
404
405 Pstart.setPz(0.5*(startPlus - startMinus));
406 Pstart.setE(0.5*(startPlus + startMinus));
407
408 Pend.setPz(0.5*(endPlus - endMinus));
409 Pend.setE(0.5*(endPlus + endMinus));
410
411 start->Set4Momentum(Pstart);
412 end->Set4Momentum(Pend);
413
414#ifdef G4_FTFDEBUG
415 G4cout << " generated string flavors " << start->GetPDGcode() << " / " << end->GetPDGcode() << G4endl;
416 G4cout << " generated string momenta: quark " << start->Get4Momentum() << "mass : " <<start->Get4Momentum().mag()<< G4endl;
417 G4cout << " generated string momenta: Diquark " << end ->Get4Momentum() << "mass : " <<end->Get4Momentum().mag()<< G4endl;
418 G4cout << " sum of ends " << Pstart+Pend << G4endl;
419 G4cout << " Original " << hadron->Get4Momentum() << G4endl;
420#endif
421
422 return string;
423}
424
425
426// --------- private methods ----------------------
427
428G4double G4QGSDiffractiveExcitation::ChooseP(G4double Pmin, G4double Pmax) const // Uzhi
429{
430// choose an x between Xmin and Xmax with P(x) ~ 1/x
431
432// to be improved...
433
434 G4double range=Pmax-Pmin; // Uzhi
435
436 if ( Pmin <= 0. || range <=0. )
437 {
438 G4cout << " Pmin, range : " << Pmin << " , " << range << G4endl;
439 throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation::ChooseP : Invalid arguments ");
440 }
441
442 G4double P;
443/* // Uzhi
444 do {
445 x=Xmin + G4UniformRand() * range;
446 } while ( Xmin/x < G4UniformRand() );
447*/ // Uzhi
448
449 P=Pmin * std::pow(Pmax/Pmin,G4UniformRand()); // Uzhi
450
451//debug-hpw cout << "DiffractiveX "<<x<<G4endl;
452 return P;
453}
454
455G4ThreeVector G4QGSDiffractiveExcitation::GaussianPt(G4double AveragePt2, G4double maxPtSquare) const // Uzhi
456{ // @@ this method is used in FTFModel as well. Should go somewhere common!
457
458 G4double Pt2;
459/* // Uzhi
460 do {
461 pt2=widthSquare * std::log( G4UniformRand() );
462 } while ( pt2 > maxPtSquare);
463*/ // Uzhi
464
465 Pt2 = -AveragePt2 * std::log(1. + G4UniformRand() * (std::exp(-maxPtSquare/AveragePt2)-1.));// Uzhi
466
467 G4double Pt=std::sqrt(Pt2);
468
469 G4double phi=G4UniformRand() * twopi;
470
471 return G4ThreeVector (Pt*std::cos(phi), Pt*std::sin(phi), 0.);
472}
473
474G4QGSDiffractiveExcitation::G4QGSDiffractiveExcitation(const G4QGSDiffractiveExcitation &)
475{
476 throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation copy contructor not meant to be called");
477}
478
479
480G4QGSDiffractiveExcitation::~G4QGSDiffractiveExcitation()
481{
482}
483
484
485const G4QGSDiffractiveExcitation & G4QGSDiffractiveExcitation::operator=(const G4QGSDiffractiveExcitation &)
486{
487 throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation = operator meant to be called");
488 return *this;
489}
490
491
492int G4QGSDiffractiveExcitation::operator==(const G4QGSDiffractiveExcitation &) const
493{
494 throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation == operator meant to be called");
495 return false;
496}
497
498int G4QGSDiffractiveExcitation::operator!=(const G4QGSDiffractiveExcitation &) const
499{
500 throw G4HadronicException(__FILE__, __LINE__, "G4QGSDiffractiveExcitation != operator meant to be called");
501 return true;
502}
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