EVGEN/AliGenPythia.cxx

   1 #include "AliGenerator.h"
   2 #include "AliGenPythia.h"
   3 #include "AliRun.h"
   4 #include "AliPythia.h"
   5 #include <TDirectory.h>
   6 #include <TFile.h>
   7 #include <TTree.h>
   8 #include <stdlib.h>
   9 #include <AliPythia.h>
  10 #include <TParticle.h>
  11 //#include <GParticle.h>
  12  ClassImp(AliGenPythia)
  13
  14 AliGenPythia::AliGenPythia()
  15                  :AliGenerator()
  16 {
  17 }
  18
  19 AliGenPythia::AliGenPythia(Int_t npart)
  20                  :AliGenerator(npart)
  21 {
  22 // default charm production at 5. 5 TeV
  23 // semimuonic decay
  24 // structure function GRVHO
  25 //
  26     fXsection  = 0.;
  27     fParentSelect.Set(5);
  28     fChildSelect.Set(5);
  29     for (Int_t i=0; i<5; i++) fParentSelect[i]=fChildSelect[i]=0;
  30     SetProcess();
  31     SetStrucFunc();
  32     ForceDecay();
  33     SetPtHard();
  34     SetEnergyCMS();
  35 }
  36
  37 AliGenPythia::~AliGenPythia()
  38 {
  39 }
  40
  41 void AliGenPythia::Init()
  42 {
  43     SetMC(new AliPythia());
  44     fPythia=(AliPythia*) fgMCEvGen;
  45 //
  46     fParentWeight=1./Float_t(fNpart);
  47 //
  48 //  Forward Paramters to the AliPythia object
  49     fPythia->DefineParticles();
  50     fPythia->SetCKIN(3,fPtHardMin);
  51     fPythia->SetCKIN(4,fPtHardMax);
  52     fPythia->ProcInit(fProcess,fEnergyCMS,fStrucFunc);
  53     fPythia->ForceDecay(fForceDecay);
  54     fPythia->LuList(0);
  55     fPythia->PyStat(2);
  56 //  Parent and Children Selection
  57     switch (fProcess)
  58     {
  59     case charm:
  60
  61         fParentSelect[0]=411;
  62         fParentSelect[1]=421;
  63         fParentSelect[2]=431;
  64         fParentSelect[3]=4122;
  65         break;
  66     case charm_unforced:
  67
  68         fParentSelect[0]=411;
  69         fParentSelect[1]=421;
  70         fParentSelect[2]=431;
  71         fParentSelect[3]=4122;
  72         break;
  73     case beauty:
  74         fParentSelect[0]=511;
  75         fParentSelect[1]=521;
  76         fParentSelect[2]=531;
  77         fParentSelect[3]=5122;
  78         break;
  79     case beauty_unforced:
  80         fParentSelect[0]=511;
  81         fParentSelect[1]=521;
  82         fParentSelect[2]=531;
  83         fParentSelect[3]=5122;
  84         break;
  85     case jpsi_chi:
  86     case jpsi:
  87         fParentSelect[0]=443;
  88         break;
  89     case mb:
  90         break;
  91     }
  92
  93     switch (fForceDecay)
  94     {
  95     case semielectronic:
  96     case dielectron:
  97     case b_jpsi_dielectron:
  98     case b_psip_dielectron:
  99         fChildSelect[0]=11;
 100         break;
 101     case semimuonic:
 102     case dimuon:
 103     case b_jpsi_dimuon:
 104     case b_psip_dimuon:
 105     case pitomu:
 106     case katomu:
 107         fChildSelect[0]=13;
 108         break;
 109     }
 110 }
 111
 112 void AliGenPythia::Generate()
 113 {
 114
 115     Float_t polar[3] =   {0,0,0};
 116     Float_t origin[3]=   {0,0,0};
 117     Float_t origin_p[3]= {0,0,0};
 118     Float_t origin0[3]=  {0,0,0};
 119     Float_t p[3], p_p[4], random[6];
 120 //  converts from mm/c to s
 121     const Float_t kconv=0.001/2.999792458e8;
 122
 123
 124 //
 125     Int_t nt=0;
 126     Int_t nt_p=0;
 127     Int_t jev=0;
 128     Int_t j;
 129
 130     fTrials=0;
 131     for (j=0;j<3;j++) origin0[j]=fOrigin[j];
 132     if(fVertexSmear==perEvent) {
 133         gMC->Rndm(random,6);
 134         for (j=0;j<3;j++) {
 135             origin0[j]+=fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
 136                 TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
 137             fPythia->SetMSTP(151,0);
 138         }
 139     } else if (fVertexSmear==perTrack) {
 140         fPythia->SetMSTP(151,0);
 141         for (j=0;j<3;j++) {
 142             fPythia->SetPARP(151+j, fOsigma[j]*10.);
 143         }
 144     }
 145     while(1)
 146     {
 147         fPythia->PyEvnt();
 148         fTrials++;
 149         TObjArray* particles = fPythia->ImportParticles();
 150         Int_t np = particles->GetEntriesFast();
 151         printf("\n **************************************************%d\n",np);
 152         Int_t nc=0;
 153         if (np == 0 ) continue;
 154         if (fProcess != mb) {
 155             for (Int_t i = 0; i<np; i++) {
 156                 TParticle *  iparticle = (TParticle *) particles->At(i);
 157                 Int_t kf = iparticle->GetPdgCode();
 158                 fChildWeight=(fPythia->GetBraPart(kf))*fParentWeight;
 159 //
 160 // Parent
 161                 if (ParentSelected(TMath::Abs(kf))) {
 162                     if (KinematicSelection(iparticle)) {
 163                         if (nc==0) {
 164 //
 165 // Store information concerning the hard scattering process
 166 //
 167                             Float_t mass_p = fPythia->GetPARI(13);
 168                             Float_t   pt_p = fPythia->GetPARI(17);
 169                             Float_t    y_p = fPythia->GetPARI(37);
 170                             Float_t  xmt_p = sqrt(pt_p*pt_p+mass_p*mass_p);
 171                             Float_t     ty = Float_t(TMath::TanH(y_p));
 172                             p_p[0] = pt_p;
 173                             p_p[1] = 0;
 174                             p_p[2] = xmt_p*ty/sqrt(1.-ty*ty);
 175                             p_p[3] = mass_p;
 176                             gAlice->SetTrack(0,-1,-1,
 177                                              p_p,origin_p,polar,
 178                                              0,"Hard Scat.",nt_p,fParentWeight);
 179                             gAlice->KeepTrack(nt_p);
 180                         }
 181                         nc++;
 182 //
 183 // store parent track information
 184                         p[0]=iparticle->Px();
 185                         p[1]=iparticle->Py();
 186                         p[2]=iparticle->Pz();
 187                         origin[0]=origin0[0]+iparticle->Vx()/10;
 188                         origin[1]=origin0[1]+iparticle->Vy()/10;
 189                         origin[2]=origin0[2]+iparticle->Vz()/10;
 190
 191                         Int_t ifch=iparticle->GetFirstDaughter();
 192                         Int_t ilch=iparticle->GetLastDaughter();
 193                         if (ifch !=0 && ilch !=0) {
 194                             gAlice->SetTrack(0,nt_p,kf,
 195                                              p,origin,polar,
 196                                              0,"Primary",nt,fParentWeight);
 197                             gAlice->KeepTrack(nt);
 198                             Int_t iparent = nt;
 199 //
 200 // Children
 201
 202                             for (Int_t j=ifch; j<=ilch; j++)
 203                             {
 204                                 TParticle *  ichild =
 205                                     (TParticle *) particles->At(j-1);
 206                                 Int_t kf = ichild->GetPdgCode();
 207 //
 208 //
 209                                 if (ChildSelected(TMath::Abs(kf))) {
 210                                     origin[0]=ichild->Vx();
 211                                     origin[1]=ichild->Vy();
 212                                     origin[2]=ichild->Vz();
 213                                     p[0]=ichild->Px();
 214                                     p[1]=ichild->Py();
 215                                     p[2]=ichild->Pz();
 216                                     Float_t tof=kconv*ichild->T();
 217                                     gAlice->SetTrack(fTrackIt, iparent, kf,
 218                                                      p,origin,polar,
 219                                                      tof,"Decay",nt,fChildWeight);
 220                                     gAlice->KeepTrack(nt);
 221                                 } // select child
 222                             } // child loop
 223                         }
 224                     } // kinematic selection
 225                 } // select particle
 226             } // particle loop
 227         } else {
 228             for (Int_t i = 0; i<np; i++) {
 229                 TParticle *  iparticle = (TParticle *) particles->At(i);
 230                 Int_t kf = iparticle->GetPdgCode();
 231                 Int_t ks = iparticle->GetStatusCode();
 232                 if (ks==1 && kf!=0 && KinematicSelection(iparticle)) {
 233                         nc++;
 234 //
 235 // store track information
 236                         p[0]=iparticle->Px();
 237                         p[1]=iparticle->Py();
 238                         p[2]=iparticle->Pz();
 239                         origin[0]=origin0[0]+iparticle->Vx()/10;
 240                         origin[1]=origin0[1]+iparticle->Vy()/10;
 241                         origin[2]=origin0[2]+iparticle->Vz()/10;
 242                         Float_t tof=kconv*iparticle->T();
 243                         gAlice->SetTrack(fTrackIt,-1,kf,p,origin,polar,
 244                                          tof,"Primary",nt);
 245                         gAlice->KeepTrack(nt);
 246                 } // select particle
 247             } // particle loop
 248             printf("\n I've put %i particles on the stack \n",nc);
 249         } // mb ?
 250         if (nc > 0) {
 251             jev+=nc;
 252             if (jev >= fNpart) {
 253                 fKineBias=Float_t(fNpart)/Float_t(fTrials);
 254                 printf("\n Trials: %i\n",fTrials);
 255                 break;
 256             }
 257         }
 258     } // event loop
 259 //  adjust weight due to kinematic selection
 260     AdjustWeights();
 261 //  get cross-section
 262     fXsection=fPythia->GetPARI(1);
 263 }
 264
 265 Bool_t AliGenPythia::ParentSelected(Int_t ip)
 266 {
 267     for (Int_t i=0; i<5; i++)
 268     {
 269         if (fParentSelect[i]==ip) return kTRUE;
 270     }
 271     return kFALSE;
 272 }
 273
 274 Bool_t AliGenPythia::ChildSelected(Int_t ip)
 275 {
 276     for (Int_t i=0; i<5; i++)
 277     {
 278         if (fChildSelect[i]==ip) return kTRUE;
 279     }
 280     return kFALSE;
 281 }
 282
 283 Bool_t AliGenPythia::KinematicSelection(TParticle *particle)
 284 {
 285     Float_t px=particle->Px();
 286     Float_t py=particle->Py();
 287     Float_t pz=particle->Pz();
 288     Float_t  e=particle->Energy();
 289
 290 //
 291 //  transverse momentum cut
 292     Float_t pt=TMath::Sqrt(px*px+py*py);
 293     if (pt > fPtMax || pt < fPtMin)
 294     {
 295 //      printf("\n failed pt cut %f %f %f \n",pt,fPtMin,fPtMax);
 296         return kFALSE;
 297     }
 298 //
 299 // momentum cut
 300     Float_t p=TMath::Sqrt(px*px+py*py+pz*pz);
 301     if (p > fPMax || p < fPMin)
 302     {
 303 //      printf("\n failed p cut %f %f %f \n",p,fPMin,fPMax);
 304         return kFALSE;
 305     }
 306
 307 //
 308 // theta cut
 309     Float_t  theta = Float_t(TMath::ATan2(Double_t(pt),Double_t(pz)));
 310     if (theta > fThetaMax || theta < fThetaMin)
 311     {
 312 //      printf("\n failed theta cut %f %f %f \n",theta,fThetaMin,fThetaMax);
 313         return kFALSE;
 314     }
 315
 316 //
 317 // rapidity cut
 318     Float_t y = 0.5*TMath::Log((e+pz)/(e-pz));
 319     if (y > fYMax || y < fYMin)
 320     {
 321 //      printf("\n failed y cut %f %f %f \n",y,fYMin,fYMax);
 322         return kFALSE;
 323     }
 324
 325 //
 326 // phi cut
 327     Float_t phi=Float_t(TMath::ATan2(Double_t(py),Double_t(px)))+TMath::Pi();
 328     if (phi > fPhiMax || phi < fPhiMin)
 329     {
 330 //      printf("\n failed phi cut %f %f %f \n",phi,fPhiMin,fPhiMax);
 331         return kFALSE;
 332     }
 333
 334     return kTRUE;
 335 }
 336 void AliGenPythia::AdjustWeights()
 337 {
 338     TClonesArray *PartArray = gAlice->Particles();
 339     TParticle *Part;
 340     Int_t ntrack=gAlice->GetNtrack();
 341     for (Int_t i=0; i<ntrack; i++) {
 342         Part= (TParticle*) PartArray->UncheckedAt(i);
 343         Part->SetWeight(Part->GetWeight()*fKineBias);
 344     }
 345 }
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