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