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 1.24  2000/09/18 10:41:35  morsch
  19 Add possibility to use nuclear structure functions from PDF library V8.
  20
  21 Revision 1.23  2000/09/14 14:05:40  morsch
  22 dito
  23
  24 Revision 1.22  2000/09/14 14:02:22  morsch
  25 - Correct conversion from mm to cm when passing particle vertex to MC.
  26 - Correct handling of fForceDecay == all.
  27
  28 Revision 1.21  2000/09/12 14:14:55  morsch
  29 Call fDecayer->ForceDecay() at the beginning of Generate().
  30
  31 Revision 1.20  2000/09/06 14:29:33  morsch
  32 Use AliPythia for event generation an AliDecayPythia for decays.
  33 Correct handling of "nodecay" option
  34
  35 Revision 1.19  2000/07/11 18:24:56  fca
  36 Coding convention corrections + few minor bug fixes
  37
  38 Revision 1.18  2000/06/30 12:40:34  morsch
  39 Pythia takes care of vertex smearing. Correct conversion from Pythia units (mm) to
  40 Geant units (cm).
  41
  42 Revision 1.17  2000/06/09 20:34:07  morsch
  43 All coding rule violations except RS3 corrected
  44
  45 Revision 1.16  2000/05/15 15:04:20  morsch
  46 The full event is written for fNtrack = -1
  47 Coding rule violations corrected.
  48
  49 Revision 1.15  2000/04/26 10:14:24  morsch
  50 Particles array has one entry more than pythia particle list. Upper bound of
  51 particle loop changed to np-1 (R. Guernane, AM)
  52
  53 Revision 1.14  2000/04/05 08:36:13  morsch
  54 Check status code of particles in Pythia event
  55 to avoid double counting as partonic state and final state particle.
  56
  57 Revision 1.13  1999/11/09 07:38:48  fca
  58 Changes for compatibility with version 2.23 of ROOT
  59
  60 Revision 1.12  1999/11/03 17:43:20  fca
  61 New version from G.Martinez & A.Morsch
  62
  63 Revision 1.11  1999/09/29 09:24:14  fca
  64 Introduction of the Copyright and cvs Log
  65 */
  66
  67 #include "AliGenPythia.h"
  68 #include "AliDecayerPythia.h"
  69 #include "AliRun.h"
  70 #include "AliPythia.h"
  71 #include "AliPDG.h"
  72 #include <TParticle.h>
  73 #include <TSystem.h>
  74
  75  ClassImp(AliGenPythia)
  76
  77 AliGenPythia::AliGenPythia()
  78                  :AliGenerator()
  79 {
  80 // Default Constructor
  81   fDecayer = new AliDecayerPythia();
  82 }
  83
  84 AliGenPythia::AliGenPythia(Int_t npart)
  85                  :AliGenerator(npart)
  86 {
  87 // default charm production at 5. 5 TeV
  88 // semimuonic decay
  89 // structure function GRVHO
  90 //
  91     fXsection  = 0.;
  92     fNucA1=0;
  93     fNucA2=0;
  94     fParentSelect.Set(5);
  95     fChildSelect.Set(5);
  96     for (Int_t i=0; i<5; i++) fParentSelect[i]=fChildSelect[i]=0;
  97     SetProcess();
  98     SetStrucFunc();
  99     SetForceDecay();
 100     SetPtHard();
 101     SetEnergyCMS();
 102     fDecayer = new AliDecayerPythia();
 103 }
 104
 105 AliGenPythia::AliGenPythia(const AliGenPythia & Pythia)
 106 {
 107 // copy constructor
 108 }
 109
 110 AliGenPythia::~AliGenPythia()
 111 {
 112 // Destructor
 113 }
 114
 115 void AliGenPythia::Init()
 116 {
 117 // Initialisation
 118   SetMC(AliPythia::Instance());
 119     fPythia=(AliPythia*) fgMCEvGen;
 120 //
 121     fParentWeight=1./Float_t(fNpart);
 122 //
 123 //  Forward Paramters to the AliPythia object
 124     //    gSystem->Exec("ln -s $ALICE_ROOT/data/Decay.table fort.1");
 125     //    fPythia->Pyupda(2,1);
 126     //    gSystem->Exec("rm fort.1");
 127
 128     fDecayer->SetForceDecay(fForceDecay);
 129     fDecayer->Init();
 130
 131
 132     fPythia->SetCKIN(3,fPtHardMin);
 133     fPythia->SetCKIN(4,fPtHardMax);
 134     if (fNucA1 > 0 && fNucA2 > 0) fPythia->SetNuclei(fNucA1, fNucA2);
 135     fPythia->ProcInit(fProcess,fEnergyCMS,fStrucFunc);
 136
 137     //    fPythia->Pylist(0);
 138     //    fPythia->Pystat(2);
 139 //  Parent and Children Selection
 140     switch (fProcess)
 141     {
 142     case charm:
 143
 144         fParentSelect[0]=411;
 145         fParentSelect[1]=421;
 146         fParentSelect[2]=431;
 147         fParentSelect[3]=4122;
 148         break;
 149     case charm_unforced:
 150
 151         fParentSelect[0]=411;
 152         fParentSelect[1]=421;
 153         fParentSelect[2]=431;
 154         fParentSelect[3]=4122;
 155         break;
 156     case beauty:
 157         fParentSelect[0]=511;
 158         fParentSelect[1]=521;
 159         fParentSelect[2]=531;
 160         fParentSelect[3]=5122;
 161         break;
 162     case beauty_unforced:
 163         fParentSelect[0]=511;
 164         fParentSelect[1]=521;
 165         fParentSelect[2]=531;
 166         fParentSelect[3]=5122;
 167         break;
 168     case jpsi_chi:
 169     case jpsi:
 170         fParentSelect[0]=443;
 171         break;
 172     case mb:
 173         break;
 174     }
 175
 176     switch (fForceDecay)
 177     {
 178     case semielectronic:
 179     case dielectron:
 180     case b_jpsi_dielectron:
 181     case b_psip_dielectron:
 182         fChildSelect[0]=kElectron;
 183         break;
 184     case semimuonic:
 185     case dimuon:
 186     case b_jpsi_dimuon:
 187     case b_psip_dimuon:
 188     case pitomu:
 189     case katomu:
 190         fChildSelect[0]=kMuonMinus;
 191         break;
 192     case hadronicD:
 193       fChildSelect[0]=kPiPlus;
 194       fChildSelect[1]=kKPlus;
 195       break;
 196     case all:
 197     case nodecay:
 198       break;
 199     }
 200 }
 201
 202 void AliGenPythia::Generate()
 203 {
 204 // Generate one event
 205     fDecayer->ForceDecay();
 206
 207     Float_t polar[3] =   {0,0,0};
 208     Float_t origin[3]=   {0,0,0};
 209     Float_t originP[3]= {0,0,0};
 210     Float_t origin0[3]=  {0,0,0};
 211     Float_t p[3], pP[4];
 212 //    Float_t random[6];
 213     static TClonesArray *particles;
 214 //  converts from mm/c to s
 215     const Float_t kconv=0.001/2.999792458e8;
 216
 217
 218 //
 219     Int_t nt=0;
 220     Int_t ntP=0;
 221     Int_t jev=0;
 222     Int_t j, kf;
 223
 224     if(!particles) particles=new TClonesArray("TParticle",1000);
 225
 226     fTrials=0;
 227     for (j=0;j<3;j++) origin0[j]=fOrigin[j];
 228     if(fVertexSmear==kPerEvent) {
 229         fPythia->SetMSTP(151,1);
 230         for (j=0;j<3;j++) {
 231             fPythia->SetPARP(151+j, fOsigma[j]/10.);
 232         }
 233     } else if (fVertexSmear==kPerTrack) {
 234         fPythia->SetMSTP(151,0);
 235     }
 236
 237     while(1)
 238     {
 239         fPythia->Pyevnt();
 240 //      fPythia->Pylist(1);
 241         fTrials++;
 242         fPythia->ImportParticles(particles,"All");
 243         Int_t np = particles->GetEntriesFast();
 244         printf("\n **************************************************%d\n",np);
 245         Int_t nc=0;
 246         if (np == 0 ) continue;
 247         if (fProcess != mb) {
 248             for (Int_t i = 0; i<np-1; i++) {
 249                 TParticle *  iparticle = (TParticle *) particles->At(i);
 250                 Int_t ks = iparticle->GetStatusCode();
 251                 kf = CheckPDGCode(iparticle->GetPdgCode());
 252                 if (ks==21) continue;
 253
 254                 fChildWeight=(fDecayer->GetPartialBranchingRatio(kf))*fParentWeight;
 255 //
 256 // Parent
 257                 if (ParentSelected(TMath::Abs(kf))) {
 258                     if (KinematicSelection(iparticle)) {
 259                         if (nc==0) {
 260 //
 261 // Store information concerning the hard scattering process
 262 //
 263                             Float_t massP  = fPythia->GetPARI(13);
 264                             Float_t   ptP  = fPythia->GetPARI(17);
 265                             Float_t    yP  = fPythia->GetPARI(37);
 266                             Float_t  xmtP  = sqrt(ptP*ptP+massP*massP);
 267                             Float_t    ty  = Float_t(TMath::TanH(yP));
 268                             pP[0] = ptP;
 269                             pP[1] = 0;
 270                             pP[2] = xmtP*ty/sqrt(1.-ty*ty);
 271                             pP[3] = massP;
 272                             gAlice->SetTrack(0,-1,-1,
 273                                              pP,originP,polar,
 274                                              0,"Hard Scat.",ntP,fParentWeight);
 275                             gAlice->KeepTrack(ntP);
 276                         }
 277                         nc++;
 278 //
 279 // store parent track information
 280                         p[0]=iparticle->Px();
 281                         p[1]=iparticle->Py();
 282                         p[2]=iparticle->Pz();
 283                         origin[0]=origin0[0]+iparticle->Vx()/10.;
 284                         origin[1]=origin0[1]+iparticle->Vy()/10.;
 285                         origin[2]=origin0[2]+iparticle->Vz()/10.;
 286
 287                         Int_t ifch=iparticle->GetFirstDaughter();
 288                         Int_t ilch=iparticle->GetLastDaughter();
 289
 290                         if ((ifch !=0 && ilch !=0) || fForceDecay == nodecay) {
 291                           Int_t trackit=0;
 292                           if (fForceDecay == nodecay) trackit = 1;
 293                             gAlice->SetTrack(trackit,ntP,kf,
 294                                              p,origin,polar,
 295                                              0,"Primary",nt,fParentWeight);
 296                             gAlice->KeepTrack(nt);
 297                             Int_t iparent = nt;
 298 //
 299 // Children
 300                             if (fForceDecay != nodecay) {
 301                               for (j=ifch; j<=ilch; j++)
 302                                 {
 303                                   TParticle *  ichild =
 304                                     (TParticle *) particles->At(j-1);
 305                                   kf = CheckPDGCode(ichild->GetPdgCode());
 306 //
 307 //
 308                                   if (ChildSelected(TMath::Abs(kf))) {
 309                                     origin[0]=origin0[0]+ichild->Vx()/10.;
 310                                     origin[1]=origin0[1]+ichild->Vy()/10.;
 311                                     origin[2]=origin0[2]+ichild->Vz()/10.;
 312                                     p[0]=ichild->Px();
 313                                     p[1]=ichild->Py();
 314                                     p[2]=ichild->Pz();
 315                                     Float_t tof=kconv*ichild->T();
 316                                     gAlice->SetTrack(fTrackIt, iparent, kf,
 317                                                      p,origin,polar,
 318                                                      tof,"Decay",nt,fChildWeight);
 319                                     gAlice->KeepTrack(nt);
 320                                   } // select child
 321                                 } // child loop
 322                             }
 323                         }
 324                     } // kinematic selection
 325                 } // select particle
 326             } // particle loop
 327         } else {
 328             for (Int_t i = 0; i<np-1; i++) {
 329                 TParticle *  iparticle = (TParticle *) particles->At(i);
 330                 kf = CheckPDGCode(iparticle->GetPdgCode());
 331                 Int_t ks = iparticle->GetStatusCode();
 332
 333                 if (ks==1 && kf!=0 && KinematicSelection(iparticle)) {
 334                         nc++;
 335 //
 336 // store track information
 337                         p[0]=iparticle->Px();
 338                         p[1]=iparticle->Py();
 339                         p[2]=iparticle->Pz();
 340                         origin[0]=origin0[0]+iparticle->Vx()/10.;
 341                         origin[1]=origin0[1]+iparticle->Vy()/10.;
 342                         origin[2]=origin0[2]+iparticle->Vz()/10.;
 343                         Float_t tof=kconv*iparticle->T();
 344                         gAlice->SetTrack(fTrackIt,-1,kf,p,origin,polar,
 345                                          tof,"Primary",nt);
 346                         gAlice->KeepTrack(nt);
 347                 } // select particle
 348             } // particle loop
 349             printf("\n I've put %i particles on the stack \n",nc);
 350         } // mb ?
 351         if (nc > 0) {
 352             jev+=nc;
 353             if (jev >= fNpart || fNpart == -1) {
 354                 fKineBias=Float_t(fNpart)/Float_t(fTrials);
 355                 printf("\n Trials: %i %i %i\n",fTrials, fNpart, jev);
 356 // Print x-section summary
 357                 fPythia->Pystat(1);
 358                 break;
 359             }
 360         }
 361     } // event loop
 362 //  adjust weight due to kinematic selection
 363     AdjustWeights();
 364 //  get cross-section
 365     fXsection=fPythia->GetPARI(1);
 366 }
 367
 368 Bool_t AliGenPythia::ParentSelected(Int_t ip)
 369 {
 370 // True if particle is in list of parent particles to be selected
 371     for (Int_t i=0; i<5; i++)
 372     {
 373         if (fParentSelect[i]==ip) return kTRUE;
 374     }
 375     return kFALSE;
 376 }
 377
 378 Bool_t AliGenPythia::ChildSelected(Int_t ip)
 379 {
 380 // True if particle is in list of decay products to be selected
 381     if (fForceDecay == all) return kTRUE;
 382
 383     for (Int_t i=0; i<5; i++)
 384     {
 385         if (fChildSelect[i]==ip) return kTRUE;
 386     }
 387     return kFALSE;
 388 }
 389
 390 Bool_t AliGenPythia::KinematicSelection(TParticle *particle)
 391 {
 392 // Perform kinematic selection
 393     Float_t px=particle->Px();
 394     Float_t py=particle->Py();
 395     Float_t pz=particle->Pz();
 396     Float_t  e=particle->Energy();
 397
 398 //
 399 //  transverse momentum cut
 400     Float_t pt=TMath::Sqrt(px*px+py*py);
 401     if (pt > fPtMax || pt < fPtMin)
 402     {
 403 //      printf("\n failed pt cut %f %f %f \n",pt,fPtMin,fPtMax);
 404         return kFALSE;
 405     }
 406 //
 407 // momentum cut
 408     Float_t p=TMath::Sqrt(px*px+py*py+pz*pz);
 409     if (p > fPMax || p < fPMin)
 410     {
 411 //      printf("\n failed p cut %f %f %f \n",p,fPMin,fPMax);
 412         return kFALSE;
 413     }
 414
 415 //
 416 // theta cut
 417     Float_t  theta = Float_t(TMath::ATan2(Double_t(pt),Double_t(pz)));
 418     if (theta > fThetaMax || theta < fThetaMin)
 419     {
 420 //      printf("\n failed theta cut %f %f %f \n",theta,fThetaMin,fThetaMax);
 421         return kFALSE;
 422     }
 423
 424 //
 425 // rapidity cut
 426     if (e==pz) {
 427       return kFALSE;
 428     }
 429     else {
 430       Float_t y = 0.5*TMath::Log((e+pz)/(e-pz));
 431       if (y > fYMax || y < fYMin)
 432         {
 433 //      printf("\n failed y cut %f %f %f \n",y,fYMin,fYMax);
 434           return kFALSE;
 435         }
 436     }
 437
 438 //
 439 // phi cut
 440     Float_t phi=Float_t(TMath::ATan2(Double_t(py),Double_t(px)));
 441     if (phi > fPhiMax || phi < fPhiMin)
 442     {
 443 //      printf("\n failed phi cut %f %f %f \n",phi,fPhiMin,fPhiMax);
 444         return kFALSE;
 445     }
 446
 447     return kTRUE;
 448 }
 449 void AliGenPythia::AdjustWeights()
 450 {
 451 // Adjust the weights after generation of all events
 452 //
 453     TClonesArray *partArray = gAlice->Particles();
 454     TParticle *part;
 455     Int_t ntrack=gAlice->GetNtrack();
 456     for (Int_t i=0; i<ntrack; i++) {
 457         part= (TParticle*) partArray->UncheckedAt(i);
 458         part->SetWeight(part->GetWeight()*fKineBias);
 459     }
 460 }
 461
 462 Int_t AliGenPythia::CheckPDGCode(Int_t pdgcode)
 463 {
 464 //
 465 //  If the particle is in a diffractive state, then take action accordingly
 466   switch (pdgcode) {
 467   case 91:
 468     return 92;
 469   case 110:
 470     //rho_diff0 -- difficult to translate, return rho0
 471     return 113;
 472   case 210:
 473     //pi_diffr+ -- change to pi+
 474     return 211;
 475   case 220:
 476     //omega_di0 -- change to omega0
 477     return 223;
 478   case 330:
 479     //phi_diff0 -- return phi0
 480     return 333;
 481   case 440:
 482     //J/psi_di0 -- return J/psi
 483     return 443;
 484   case 2110:
 485     //n_diffr -- return neutron
 486     return 2112;
 487   case 2210:
 488     //p_diffr+ -- return proton
 489     return 2212;
 490   }
 491   //non diffractive state -- return code unchanged
 492   return pdgcode;
 493 }
 494
 495
 496 void AliGenPythia::SetNuclei(Int_t a1, Int_t a2)
 497 {
 498 // Treat protons as inside nuclei with mass numbers a1 and a2
 499     fNucA1 = a1;
 500     fNucA2 = a2;
 501 }
 502
 503
 504 AliGenPythia& AliGenPythia::operator=(const  AliGenPythia& rhs)
 505 {
 506 // Assignment operator
 507     return *this;
 508 }
 509
 510
 511
 512 void AliGenPythia::Streamer(TBuffer &R__b)
 513 {
 514    // Stream an object of class AliGenPythia.
 515
 516    if (R__b.IsReading()) {
 517       Version_t R__v = R__b.ReadVersion(); if (R__v) { }
 518       AliGenerator::Streamer(R__b);
 519       R__b >> (Int_t&)fProcess;
 520       R__b >> (Int_t&)fStrucFunc;
 521       R__b >> (Int_t&)fForceDecay;
 522       R__b >> fEnergyCMS;
 523       R__b >> fKineBias;
 524       R__b >> fTrials;
 525       fParentSelect.Streamer(R__b);
 526       fChildSelect.Streamer(R__b);
 527       R__b >> fXsection;
 528 //      (AliPythia::Instance())->Streamer(R__b);
 529       R__b >> fPtHardMin;
 530       R__b >> fPtHardMax;
 531 //      if (fDecayer) fDecayer->Streamer(R__b);
 532    } else {
 533       R__b.WriteVersion(AliGenPythia::IsA());
 534       AliGenerator::Streamer(R__b);
 535       R__b << (Int_t)fProcess;
 536       R__b << (Int_t)fStrucFunc;
 537       R__b << (Int_t)fForceDecay;
 538       R__b << fEnergyCMS;
 539       R__b << fKineBias;
 540       R__b << fTrials;
 541       fParentSelect.Streamer(R__b);
 542       fChildSelect.Streamer(R__b);
 543       R__b << fXsection;
 544 //      R__b << fPythia;
 545       R__b << fPtHardMin;
 546       R__b << fPtHardMax;
 547       //     fDecayer->Streamer(R__b);
 548    }
 549 }
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