EVGEN/AliGenPythia.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
   3  *                                                                        *
   4  * Author: The ALICE Off-line Project.                                    *
   5  * Contributors are mentioned in the code where appropriate.              *
   6  *                                                                        *
   7  * Permission to use, copy, modify and distribute this software and its   *
   8  * documentation strictly for non-commercial purposes is hereby granted   *
   9  * without fee, provided that the above copyright notice appears in all   *
  10  * copies and that both the copyright notice and this permission notice   *
  11  * appear in the supporting documentation. The authors make no claims     *
  12  * about the suitability of this software for any purpose. It is          *
  13  * provided "as is" without express or implied warranty.                  *
  14  **************************************************************************/
  15
  16 /*
  17 $Log$
  18 Revision 1.18  2000/06/30 12:40:34  morsch
  19 Pythia takes care of vertex smearing. Correct conversion from Pythia units (mm) to
  20 Geant units (cm).
  21
  22 Revision 1.17  2000/06/09 20:34:07  morsch
  23 All coding rule violations except RS3 corrected
  24
  25 Revision 1.16  2000/05/15 15:04:20  morsch
  26 The full event is written for fNtrack = -1
  27 Coding rule violations corrected.
  28
  29 Revision 1.15  2000/04/26 10:14:24  morsch
  30 Particles array has one entry more than pythia particle list. Upper bound of
  31 particle loop changed to np-1 (R. Guernane, AM)
  32
  33 Revision 1.14  2000/04/05 08:36:13  morsch
  34 Check status code of particles in Pythia event
  35 to avoid double counting as partonic state and final state particle.
  36
  37 Revision 1.13  1999/11/09 07:38:48  fca
  38 Changes for compatibility with version 2.23 of ROOT
  39
  40 Revision 1.12  1999/11/03 17:43:20  fca
  41 New version from G.Martinez & A.Morsch
  42
  43 Revision 1.11  1999/09/29 09:24:14  fca
  44 Introduction of the Copyright and cvs Log
  45 */
  46
  47 #include "AliGenPythia.h"
  48 #include "AliRun.h"
  49 #include "AliPythia.h"
  50 #include <TParticle.h>
  51
  52  ClassImp(AliGenPythia)
  53
  54 AliGenPythia::AliGenPythia()
  55                  :AliGenerator()
  56 {
  57 // Constructor
  58 }
  59
  60 AliGenPythia::AliGenPythia(Int_t npart)
  61                  :AliGenerator(npart)
  62 {
  63 // default charm production at 5. 5 TeV
  64 // semimuonic decay
  65 // structure function GRVHO
  66 //
  67     fXsection  = 0.;
  68     fParentSelect.Set(5);
  69     fChildSelect.Set(5);
  70     for (Int_t i=0; i<5; i++) fParentSelect[i]=fChildSelect[i]=0;
  71     SetProcess();
  72     SetStrucFunc();
  73     SetForceDecay();
  74     SetPtHard();
  75     SetEnergyCMS();
  76 }
  77
  78 AliGenPythia::AliGenPythia(const AliGenPythia & Pythia)
  79 {
  80 // copy constructor
  81 }
  82
  83 AliGenPythia::~AliGenPythia()
  84 {
  85 // Destructor
  86 }
  87
  88 void AliGenPythia::Init()
  89 {
  90 // Initialisation
  91     SetMC(new AliPythia());
  92     fPythia=(AliPythia*) fgMCEvGen;
  93 //
  94     fParentWeight=1./Float_t(fNpart);
  95 //
  96 //  Forward Paramters to the AliPythia object
  97     fPythia->DefineParticles();
  98     fPythia->SetCKIN(3,fPtHardMin);
  99     fPythia->SetCKIN(4,fPtHardMax);
 100     fPythia->ProcInit(fProcess,fEnergyCMS,fStrucFunc);
 101     fPythia->ForceDecay(fForceDecay);
 102     fPythia->Lulist(0);
 103     fPythia->Pystat(2);
 104 //  Parent and Children Selection
 105     switch (fProcess)
 106     {
 107     case charm:
 108
 109         fParentSelect[0]=411;
 110         fParentSelect[1]=421;
 111         fParentSelect[2]=431;
 112         fParentSelect[3]=4122;
 113         break;
 114     case charm_unforced:
 115
 116         fParentSelect[0]=411;
 117         fParentSelect[1]=421;
 118         fParentSelect[2]=431;
 119         fParentSelect[3]=4122;
 120         break;
 121     case beauty:
 122         fParentSelect[0]=511;
 123         fParentSelect[1]=521;
 124         fParentSelect[2]=531;
 125         fParentSelect[3]=5122;
 126         break;
 127     case beauty_unforced:
 128         fParentSelect[0]=511;
 129         fParentSelect[1]=521;
 130         fParentSelect[2]=531;
 131         fParentSelect[3]=5122;
 132         break;
 133     case jpsi_chi:
 134     case jpsi:
 135         fParentSelect[0]=443;
 136         break;
 137     case mb:
 138         break;
 139     }
 140
 141     switch (fForceDecay)
 142     {
 143     case semielectronic:
 144     case dielectron:
 145     case b_jpsi_dielectron:
 146     case b_psip_dielectron:
 147         fChildSelect[0]=11;
 148         break;
 149     case semimuonic:
 150     case dimuon:
 151     case b_jpsi_dimuon:
 152     case b_psip_dimuon:
 153     case pitomu:
 154     case katomu:
 155         fChildSelect[0]=13;
 156         break;
 157     case all:
 158     case nodecay:
 159         break;
 160     }
 161 }
 162
 163 void AliGenPythia::Generate()
 164 {
 165 // Generate one event
 166
 167     Float_t polar[3] =   {0,0,0};
 168     Float_t origin[3]=   {0,0,0};
 169     Float_t originP[3]= {0,0,0};
 170     Float_t origin0[3]=  {0,0,0};
 171     Float_t p[3], pP[4];
 172 //    Float_t random[6];
 173     static TClonesArray *particles;
 174 //  converts from mm/c to s
 175     const Float_t kconv=0.001/2.999792458e8;
 176
 177
 178 //
 179     Int_t nt=0;
 180     Int_t ntP=0;
 181     Int_t jev=0;
 182     Int_t j, kf;
 183
 184     if(!particles) particles=new TClonesArray("TParticle",1000);
 185
 186     fTrials=0;
 187     for (j=0;j<3;j++) origin0[j]=fOrigin[j];
 188     if(fVertexSmear==kPerEvent) {
 189         fPythia->SetMSTP(151,1);
 190         for (j=0;j<3;j++) {
 191             fPythia->SetPARP(151+j, fOsigma[j]/10.);
 192         }
 193     } else if (fVertexSmear==kPerTrack) {
 194         fPythia->SetMSTP(151,0);
 195     }
 196
 197     while(1)
 198     {
 199         fPythia->Pyevnt();
 200 //      fPythia->Lulist(1);
 201         fTrials++;
 202         fPythia->ImportParticles(particles,"All");
 203         Int_t np = particles->GetEntriesFast();
 204         printf("\n **************************************************%d\n",np);
 205         Int_t nc=0;
 206         if (np == 0 ) continue;
 207         if (fProcess != mb) {
 208             for (Int_t i = 0; i<np-1; i++) {
 209                 TParticle *  iparticle = (TParticle *) particles->At(i);
 210                 Int_t ks = iparticle->GetStatusCode();
 211                 kf = CheckPDGCode(iparticle->GetPdgCode());
 212                 if (ks==21) continue;
 213
 214                 fChildWeight=(fPythia->GetBraPart(kf))*fParentWeight;
 215 //
 216 // Parent
 217                 if (ParentSelected(TMath::Abs(kf))) {
 218                     if (KinematicSelection(iparticle)) {
 219                         if (nc==0) {
 220 //
 221 // Store information concerning the hard scattering process
 222 //
 223                             Float_t massP  = fPythia->GetPARI(13);
 224                             Float_t   ptP  = fPythia->GetPARI(17);
 225                             Float_t    yP  = fPythia->GetPARI(37);
 226                             Float_t  xmtP  = sqrt(ptP*ptP+massP*massP);
 227                             Float_t    ty  = Float_t(TMath::TanH(yP));
 228                             pP[0] = ptP;
 229                             pP[1] = 0;
 230                             pP[2] = xmtP*ty/sqrt(1.-ty*ty);
 231                             pP[3] = massP;
 232                             gAlice->SetTrack(0,-1,-1,
 233                                              pP,originP,polar,
 234                                              0,"Hard Scat.",ntP,fParentWeight);
 235                             gAlice->KeepTrack(ntP);
 236                         }
 237                         nc++;
 238 //
 239 // store parent track information
 240                         p[0]=iparticle->Px();
 241                         p[1]=iparticle->Py();
 242                         p[2]=iparticle->Pz();
 243                         origin[0]=origin0[0]+iparticle->Vx()*10.;
 244                         origin[1]=origin0[1]+iparticle->Vy()*10.;
 245                         origin[2]=origin0[2]+iparticle->Vz()*10.;
 246
 247                         Int_t ifch=iparticle->GetFirstDaughter();
 248                         Int_t ilch=iparticle->GetLastDaughter();
 249                         if (ifch !=0 && ilch !=0) {
 250                             gAlice->SetTrack(0,ntP,kf,
 251                                              p,origin,polar,
 252                                              0,"Primary",nt,fParentWeight);
 253                             gAlice->KeepTrack(nt);
 254                             Int_t iparent = nt;
 255 //
 256 // Children
 257
 258                             for (j=ifch; j<=ilch; j++)
 259                             {
 260                                 TParticle *  ichild =
 261                                     (TParticle *) particles->At(j-1);
 262                                 kf = CheckPDGCode(ichild->GetPdgCode());
 263 //
 264 //
 265                                 if (ChildSelected(TMath::Abs(kf))) {
 266                                     origin[0]=origin0[0]+ichild->Vx()*10.;
 267                                     origin[1]=origin0[1]+ichild->Vy()*10.;
 268                                     origin[2]=origin0[2]+ichild->Vz()*10.;
 269                                     p[0]=ichild->Px();
 270                                     p[1]=ichild->Py();
 271                                     p[2]=ichild->Pz();
 272                                     Float_t tof=kconv*ichild->T();
 273                                     gAlice->SetTrack(fTrackIt, iparent, kf,
 274                                                      p,origin,polar,
 275                                                      tof,"Decay",nt,fChildWeight);
 276                                     gAlice->KeepTrack(nt);
 277                                 } // select child
 278                             } // child loop
 279                         }
 280                     } // kinematic selection
 281                 } // select particle
 282             } // particle loop
 283         } else {
 284             for (Int_t i = 0; i<np-1; i++) {
 285                 TParticle *  iparticle = (TParticle *) particles->At(i);
 286                 kf = CheckPDGCode(iparticle->GetPdgCode());
 287                 Int_t ks = iparticle->GetStatusCode();
 288
 289                 if (ks==1 && kf!=0 && KinematicSelection(iparticle)) {
 290                         nc++;
 291 //
 292 // store track information
 293                         p[0]=iparticle->Px();
 294                         p[1]=iparticle->Py();
 295                         p[2]=iparticle->Pz();
 296                         origin[0]=origin0[0]+iparticle->Vx()*10;
 297                         origin[1]=origin0[1]+iparticle->Vy()*10;
 298                         origin[2]=origin0[2]+iparticle->Vz()*10;
 299                         Float_t tof=kconv*iparticle->T();
 300                         gAlice->SetTrack(fTrackIt,-1,kf,p,origin,polar,
 301                                          tof,"Primary",nt);
 302                         gAlice->KeepTrack(nt);
 303                 } // select particle
 304             } // particle loop
 305             printf("\n I've put %i particles on the stack \n",nc);
 306         } // mb ?
 307         if (nc > 0) {
 308             jev+=nc;
 309             if (jev >= fNpart || fNpart == -1) {
 310                 fKineBias=Float_t(fNpart)/Float_t(fTrials);
 311                 printf("\n Trials: %i %i %i\n",fTrials, fNpart, jev);
 312                 break;
 313             }
 314         }
 315     } // event loop
 316 //  adjust weight due to kinematic selection
 317     AdjustWeights();
 318 //  get cross-section
 319     fXsection=fPythia->GetPARI(1);
 320 }
 321
 322 Bool_t AliGenPythia::ParentSelected(Int_t ip)
 323 {
 324 // True if particle is in list of parent particles to be selected
 325     for (Int_t i=0; i<5; i++)
 326     {
 327         if (fParentSelect[i]==ip) return kTRUE;
 328     }
 329     return kFALSE;
 330 }
 331
 332 Bool_t AliGenPythia::ChildSelected(Int_t ip)
 333 {
 334 // True if particle is in list of decay products to be selected
 335     for (Int_t i=0; i<5; i++)
 336     {
 337         if (fChildSelect[i]==ip) return kTRUE;
 338     }
 339     return kFALSE;
 340 }
 341
 342 Bool_t AliGenPythia::KinematicSelection(TParticle *particle)
 343 {
 344 // Perform kinematic selection
 345     Float_t px=particle->Px();
 346     Float_t py=particle->Py();
 347     Float_t pz=particle->Pz();
 348     Float_t  e=particle->Energy();
 349
 350 //
 351 //  transverse momentum cut
 352     Float_t pt=TMath::Sqrt(px*px+py*py);
 353     if (pt > fPtMax || pt < fPtMin)
 354     {
 355 //      printf("\n failed pt cut %f %f %f \n",pt,fPtMin,fPtMax);
 356         return kFALSE;
 357     }
 358 //
 359 // momentum cut
 360     Float_t p=TMath::Sqrt(px*px+py*py+pz*pz);
 361     if (p > fPMax || p < fPMin)
 362     {
 363 //      printf("\n failed p cut %f %f %f \n",p,fPMin,fPMax);
 364         return kFALSE;
 365     }
 366
 367 //
 368 // theta cut
 369     Float_t  theta = Float_t(TMath::ATan2(Double_t(pt),Double_t(pz)));
 370     if (theta > fThetaMax || theta < fThetaMin)
 371     {
 372 //      printf("\n failed theta cut %f %f %f \n",theta,fThetaMin,fThetaMax);
 373         return kFALSE;
 374     }
 375
 376 //
 377 // rapidity cut
 378     Float_t y = 0.5*TMath::Log((e+pz)/(e-pz));
 379     if (y > fYMax || y < fYMin)
 380     {
 381 //      printf("\n failed y cut %f %f %f \n",y,fYMin,fYMax);
 382         return kFALSE;
 383     }
 384
 385 //
 386 // phi cut
 387     Float_t phi=Float_t(TMath::ATan2(Double_t(py),Double_t(px)));
 388     if (phi > fPhiMax || phi < fPhiMin)
 389     {
 390 //      printf("\n failed phi cut %f %f %f \n",phi,fPhiMin,fPhiMax);
 391         return kFALSE;
 392     }
 393
 394     return kTRUE;
 395 }
 396 void AliGenPythia::AdjustWeights()
 397 {
 398 // Adjust the weights after generation of all events
 399 //
 400     TClonesArray *partArray = gAlice->Particles();
 401     TParticle *part;
 402     Int_t ntrack=gAlice->GetNtrack();
 403     for (Int_t i=0; i<ntrack; i++) {
 404         part= (TParticle*) partArray->UncheckedAt(i);
 405         part->SetWeight(part->GetWeight()*fKineBias);
 406     }
 407 }
 408
 409 Int_t AliGenPythia::CheckPDGCode(Int_t pdgcode)
 410 {
 411 //
 412 //  If the particle is in a diffractive state, then take action accordingly
 413   switch (pdgcode) {
 414   case 110:
 415     //rho_diff0 -- difficult to translate, return rho0
 416     return 113;
 417   case 210:
 418     //pi_diffr+ -- change to pi+
 419     return 211;
 420   case 220:
 421     //omega_di0 -- change to omega0
 422     return 223;
 423   case 330:
 424     //phi_diff0 -- return phi0
 425     return 333;
 426   case 440:
 427     //J/psi_di0 -- return J/psi
 428     return 443;
 429   case 2110:
 430     //n_diffr -- return neutron
 431     return 2112;
 432   case 2210:
 433     //p_diffr+ -- return proton
 434     return 2212;
 435   }
 436   //non diffractive state -- return code unchanged
 437   return pdgcode;
 438 }
 439
 440 AliGenPythia& AliGenPythia::operator=(const  AliGenPythia& rhs)
 441 {
 442 // Assignment operator
 443     return *this;
 444 }
 445
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