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 1.12  1999/11/03 17:43:20  fca
  19 New version from G.Martinez & A.Morsch
  20
  21 Revision 1.11  1999/09/29 09:24:14  fca
  22 Introduction of the Copyright and cvs Log
  23 */
  24
  25 #include "AliGenerator.h"
  26 #include "AliGenPythia.h"
  27 #include "AliRun.h"
  28 #include "AliPythia.h"
  29 #include <TDirectory.h>
  30 #include <TFile.h>
  31 #include <TTree.h>
  32 #include <stdlib.h>
  33 #include <AliPythia.h>
  34 #include <TParticle.h>
  35 //#include <GParticle.h>
  36  ClassImp(AliGenPythia)
  37
  38 AliGenPythia::AliGenPythia()
  39                  :AliGenerator()
  40 {
  41 }
  42
  43 AliGenPythia::AliGenPythia(Int_t npart)
  44                  :AliGenerator(npart)
  45 {
  46 // default charm production at 5. 5 TeV
  47 // semimuonic decay
  48 // structure function GRVHO
  49 //
  50     fXsection  = 0.;
  51     fParentSelect.Set(5);
  52     fChildSelect.Set(5);
  53     for (Int_t i=0; i<5; i++) fParentSelect[i]=fChildSelect[i]=0;
  54     SetProcess();
  55     SetStrucFunc();
  56     SetForceDecay();
  57     SetPtHard();
  58     SetEnergyCMS();
  59 }
  60
  61 AliGenPythia::~AliGenPythia()
  62 {
  63 }
  64
  65 void AliGenPythia::Init()
  66 {
  67     SetMC(new AliPythia());
  68     fPythia=(AliPythia*) fgMCEvGen;
  69 //
  70     fParentWeight=1./Float_t(fNpart);
  71 //
  72 //  Forward Paramters to the AliPythia object
  73     fPythia->DefineParticles();
  74     fPythia->SetCKIN(3,fPtHardMin);
  75     fPythia->SetCKIN(4,fPtHardMax);
  76     fPythia->ProcInit(fProcess,fEnergyCMS,fStrucFunc);
  77     fPythia->ForceDecay(fForceDecay);
  78     fPythia->Lulist(0);
  79     fPythia->Pystat(2);
  80 //  Parent and Children Selection
  81     switch (fProcess)
  82     {
  83     case charm:
  84
  85         fParentSelect[0]=411;
  86         fParentSelect[1]=421;
  87         fParentSelect[2]=431;
  88         fParentSelect[3]=4122;
  89         break;
  90     case charm_unforced:
  91
  92         fParentSelect[0]=411;
  93         fParentSelect[1]=421;
  94         fParentSelect[2]=431;
  95         fParentSelect[3]=4122;
  96         break;
  97     case beauty:
  98         fParentSelect[0]=511;
  99         fParentSelect[1]=521;
 100         fParentSelect[2]=531;
 101         fParentSelect[3]=5122;
 102         break;
 103     case beauty_unforced:
 104         fParentSelect[0]=511;
 105         fParentSelect[1]=521;
 106         fParentSelect[2]=531;
 107         fParentSelect[3]=5122;
 108         break;
 109     case jpsi_chi:
 110     case jpsi:
 111         fParentSelect[0]=443;
 112         break;
 113     case mb:
 114         break;
 115     }
 116
 117     switch (fForceDecay)
 118     {
 119     case semielectronic:
 120     case dielectron:
 121     case b_jpsi_dielectron:
 122     case b_psip_dielectron:
 123         fChildSelect[0]=11;
 124         break;
 125     case semimuonic:
 126     case dimuon:
 127     case b_jpsi_dimuon:
 128     case b_psip_dimuon:
 129     case pitomu:
 130     case katomu:
 131         fChildSelect[0]=13;
 132         break;
 133     case all:
 134     case nodecay:
 135         break;
 136     }
 137 }
 138
 139 void AliGenPythia::Generate()
 140 {
 141
 142     Float_t polar[3] =   {0,0,0};
 143     Float_t origin[3]=   {0,0,0};
 144     Float_t origin_p[3]= {0,0,0};
 145     Float_t origin0[3]=  {0,0,0};
 146     Float_t p[3], p_p[4], random[6];
 147     static TClonesArray *particles;
 148 //  converts from mm/c to s
 149     const Float_t kconv=0.001/2.999792458e8;
 150
 151
 152 //
 153     Int_t nt=0;
 154     Int_t nt_p=0;
 155     Int_t jev=0;
 156     Int_t j, kf;
 157
 158     if(!particles) particles=new TClonesArray("TParticle",1000);
 159
 160     fTrials=0;
 161     for (j=0;j<3;j++) origin0[j]=fOrigin[j];
 162     if(fVertexSmear==perEvent) {
 163         gMC->Rndm(random,6);
 164         for (j=0;j<3;j++) {
 165             origin0[j]+=fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
 166                 TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
 167             fPythia->SetMSTP(151,0);
 168         }
 169     } else if (fVertexSmear==perTrack) {
 170         fPythia->SetMSTP(151,0);
 171         for (j=0;j<3;j++) {
 172             fPythia->SetPARP(151+j, fOsigma[j]*10.);
 173         }
 174     }
 175     while(1)
 176     {
 177         fPythia->Pyevnt();
 178         fTrials++;
 179         fPythia->ImportParticles(particles,"All");
 180         Int_t np = particles->GetEntriesFast();
 181         printf("\n **************************************************%d\n",np);
 182         Int_t nc=0;
 183         if (np == 0 ) continue;
 184         if (fProcess != mb) {
 185             for (Int_t i = 0; i<np; i++) {
 186                 TParticle *  iparticle = (TParticle *) particles->At(i);
 187                 kf = CheckPDGCode(iparticle->GetPdgCode());
 188                 fChildWeight=(fPythia->GetBraPart(kf))*fParentWeight;
 189 //
 190 // Parent
 191                 if (ParentSelected(TMath::Abs(kf))) {
 192                     if (KinematicSelection(iparticle)) {
 193                         if (nc==0) {
 194 //
 195 // Store information concerning the hard scattering process
 196 //
 197                             Float_t mass_p = fPythia->GetPARI(13);
 198                             Float_t   pt_p = fPythia->GetPARI(17);
 199                             Float_t    y_p = fPythia->GetPARI(37);
 200                             Float_t  xmt_p = sqrt(pt_p*pt_p+mass_p*mass_p);
 201                             Float_t     ty = Float_t(TMath::TanH(y_p));
 202                             p_p[0] = pt_p;
 203                             p_p[1] = 0;
 204                             p_p[2] = xmt_p*ty/sqrt(1.-ty*ty);
 205                             p_p[3] = mass_p;
 206                             gAlice->SetTrack(0,-1,-1,
 207                                              p_p,origin_p,polar,
 208                                              0,"Hard Scat.",nt_p,fParentWeight);
 209                             gAlice->KeepTrack(nt_p);
 210                         }
 211                         nc++;
 212 //
 213 // store parent track information
 214                         p[0]=iparticle->Px();
 215                         p[1]=iparticle->Py();
 216                         p[2]=iparticle->Pz();
 217                         origin[0]=origin0[0]+iparticle->Vx()/10;
 218                         origin[1]=origin0[1]+iparticle->Vy()/10;
 219                         origin[2]=origin0[2]+iparticle->Vz()/10;
 220
 221                         Int_t ifch=iparticle->GetFirstDaughter();
 222                         Int_t ilch=iparticle->GetLastDaughter();
 223                         if (ifch !=0 && ilch !=0) {
 224                             gAlice->SetTrack(0,nt_p,kf,
 225                                              p,origin,polar,
 226                                              0,"Primary",nt,fParentWeight);
 227                             gAlice->KeepTrack(nt);
 228                             Int_t iparent = nt;
 229 //
 230 // Children
 231
 232                             for (j=ifch; j<=ilch; j++)
 233                             {
 234                                 TParticle *  ichild =
 235                                     (TParticle *) particles->At(j-1);
 236                                 kf = CheckPDGCode(ichild->GetPdgCode());
 237 //
 238 //
 239                                 if (ChildSelected(TMath::Abs(kf))) {
 240                                     origin[0]=ichild->Vx();
 241                                     origin[1]=ichild->Vy();
 242                                     origin[2]=ichild->Vz();
 243                                     p[0]=ichild->Px();
 244                                     p[1]=ichild->Py();
 245                                     p[2]=ichild->Pz();
 246                                     Float_t tof=kconv*ichild->T();
 247                                     gAlice->SetTrack(fTrackIt, iparent, kf,
 248                                                      p,origin,polar,
 249                                                      tof,"Decay",nt,fChildWeight);
 250                                     gAlice->KeepTrack(nt);
 251                                 } // select child
 252                             } // child loop
 253                         }
 254                     } // kinematic selection
 255                 } // select particle
 256             } // particle loop
 257         } else {
 258             for (Int_t i = 0; i<np; i++) {
 259                 TParticle *  iparticle = (TParticle *) particles->At(i);
 260                 kf = CheckPDGCode(iparticle->GetPdgCode());
 261                 Int_t ks = iparticle->GetStatusCode();
 262                 if (ks==1 && kf!=0 && KinematicSelection(iparticle)) {
 263                         nc++;
 264 //
 265 // store track information
 266                         p[0]=iparticle->Px();
 267                         p[1]=iparticle->Py();
 268                         p[2]=iparticle->Pz();
 269                         origin[0]=origin0[0]+iparticle->Vx()/10;
 270                         origin[1]=origin0[1]+iparticle->Vy()/10;
 271                         origin[2]=origin0[2]+iparticle->Vz()/10;
 272                         Float_t tof=kconv*iparticle->T();
 273                         gAlice->SetTrack(fTrackIt,-1,kf,p,origin,polar,
 274                                          tof,"Primary",nt);
 275                         gAlice->KeepTrack(nt);
 276                 } // select particle
 277             } // particle loop
 278             printf("\n I've put %i particles on the stack \n",nc);
 279         } // mb ?
 280         if (nc > 0) {
 281             jev+=nc;
 282             if (jev >= fNpart) {
 283                 fKineBias=Float_t(fNpart)/Float_t(fTrials);
 284                 printf("\n Trials: %i\n",fTrials);
 285                 break;
 286             }
 287         }
 288     } // event loop
 289 //  adjust weight due to kinematic selection
 290     AdjustWeights();
 291 //  get cross-section
 292     fXsection=fPythia->GetPARI(1);
 293 }
 294
 295 Bool_t AliGenPythia::ParentSelected(Int_t ip)
 296 {
 297     for (Int_t i=0; i<5; i++)
 298     {
 299         if (fParentSelect[i]==ip) return kTRUE;
 300     }
 301     return kFALSE;
 302 }
 303
 304 Bool_t AliGenPythia::ChildSelected(Int_t ip)
 305 {
 306     for (Int_t i=0; i<5; i++)
 307     {
 308         if (fChildSelect[i]==ip) return kTRUE;
 309     }
 310     return kFALSE;
 311 }
 312
 313 Bool_t AliGenPythia::KinematicSelection(TParticle *particle)
 314 {
 315     Float_t px=particle->Px();
 316     Float_t py=particle->Py();
 317     Float_t pz=particle->Pz();
 318     Float_t  e=particle->Energy();
 319
 320 //
 321 //  transverse momentum cut
 322     Float_t pt=TMath::Sqrt(px*px+py*py);
 323     if (pt > fPtMax || pt < fPtMin)
 324     {
 325 //      printf("\n failed pt cut %f %f %f \n",pt,fPtMin,fPtMax);
 326         return kFALSE;
 327     }
 328 //
 329 // momentum cut
 330     Float_t p=TMath::Sqrt(px*px+py*py+pz*pz);
 331     if (p > fPMax || p < fPMin)
 332     {
 333 //      printf("\n failed p cut %f %f %f \n",p,fPMin,fPMax);
 334         return kFALSE;
 335     }
 336
 337 //
 338 // theta cut
 339     Float_t  theta = Float_t(TMath::ATan2(Double_t(pt),Double_t(pz)));
 340     if (theta > fThetaMax || theta < fThetaMin)
 341     {
 342 //      printf("\n failed theta cut %f %f %f \n",theta,fThetaMin,fThetaMax);
 343         return kFALSE;
 344     }
 345
 346 //
 347 // rapidity cut
 348     Float_t y = 0.5*TMath::Log((e+pz)/(e-pz));
 349     if (y > fYMax || y < fYMin)
 350     {
 351 //      printf("\n failed y cut %f %f %f \n",y,fYMin,fYMax);
 352         return kFALSE;
 353     }
 354
 355 //
 356 // phi cut
 357     Float_t phi=Float_t(TMath::ATan2(Double_t(py),Double_t(px)))+TMath::Pi();
 358     if (phi > fPhiMax || phi < fPhiMin)
 359     {
 360 //      printf("\n failed phi cut %f %f %f \n",phi,fPhiMin,fPhiMax);
 361         return kFALSE;
 362     }
 363
 364     return kTRUE;
 365 }
 366 void AliGenPythia::AdjustWeights()
 367 {
 368     TClonesArray *PartArray = gAlice->Particles();
 369     TParticle *Part;
 370     Int_t ntrack=gAlice->GetNtrack();
 371     for (Int_t i=0; i<ntrack; i++) {
 372         Part= (TParticle*) PartArray->UncheckedAt(i);
 373         Part->SetWeight(Part->GetWeight()*fKineBias);
 374     }
 375 }
 376
 377 Int_t AliGenPythia::CheckPDGCode(Int_t pdgcode)
 378 {
 379 //
 380 //  If the particle is in a diffractive state, then take action accordigly
 381   switch (pdgcode) {
 382   case 110:
 383     //rho_diff0 -- difficult to translate, return rho0
 384     return 113;
 385   case 210:
 386     //pi_diffr+ -- change to pi+
 387     return 211;
 388   case 220:
 389     //omega_di0 -- change to omega0
 390     return 223;
 391   case 330:
 392     //phi_diff0 -- return phi0
 393     return 333;
 394   case 440:
 395     //J/psi_di0 -- return J/psi
 396     return 443;
 397   case 2110:
 398     //n_diffr -- return neutron
 399     return 2112;
 400   case 2210:
 401     //p_diffr+ -- return proton
 402     return 2212;
 403   }
 404   //non diffractive state -- return code unchanged
 405   return pdgcode;
 406 }
 407
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