sim_muo_P8(Int_t rng=0, Int_t nEvents=20, Float_t momentum = 15.){
  TStopwatch timer;
  timer.Start();
  gDebug=0;
  // Load basic libraries
  // If it does not work,  please check the path of the libs and put it by hands
  gROOT->LoadMacro("$VMCWORKDIR/gconfig/rootlogon.C");
  rootlogon();

  gRandom->SetSeed(rng);
  cout<<"SEED "<<gRandom->GetSeed()<<endl;
  
  TString digiFile = "all.par";
  TString parFile = "params_tpc_P8back_4_01.root";
  //TString parFile = "params.root"; // in org sim card
  
  FairRunSim *fRun = new FairRunSim();

  // set the MC version used
  // ------------------------

  fRun->SetName("TGeant3");
  //fRun->SetName("TGeant4");

  fRun->SetOutputFile("back_P8_4_01.root");
 
  // Set the parameters
  //-------------------------------
  TString allDigiFile = gSystem->Getenv("VMCWORKDIR");
  allDigiFile += "/macro/params/";
  allDigiFile += digiFile;
 
  FairRuntimeDb* rtdb = fRun->GetRuntimeDb();
  FairParAsciiFileIo* parIo1 = new FairParAsciiFileIo();
  parIo1->open(allDigiFile.Data(),"in");
  rtdb->setFirstInput(parIo1);        
  Bool_t kParameterMerged=kTRUE;
	
  FairParRootFileIo* output=new FairParRootFileIo(kParameterMerged);
  output->open(parFile);
  rtdb->setOutput(output);
  
  // Set Material file Name
  //-----------------------
  fRun->SetMaterials("media_pnd.geo");

  // Create and add detectors
  //-------------------------
  FairModule *Cave= new PndCave("CAVE");
  Cave->SetGeometryFileName("pndcave.geo");
  fRun->AddModule(Cave); 

  FairModule *Magnet= new PndMagnet("MAGNET");
  //Magnet->SetGeometryFileName("FullSolenoid_V842.root");
  Magnet->SetGeometryFileName("FullSuperconductingSolenoid_v831.root");
  fRun->AddModule(Magnet);

  FairModule *Dipole= new PndMagnet("MAGNET");
  Dipole->SetGeometryFileName("dipole.geo");
  fRun->AddModule(Dipole);

  FairModule *Pipe= new PndPipe("PIPE");
  //fRun->AddModule(Pipe);

   FairDetector *Tpc = new PndTpcDetector("TPC", kTRUE);
  Tpc->SetGeometryFileName("tpc.geo");
  fRun->AddModule(Tpc);

  FairDetector *Mvd = new PndMvdDetector("MVD", kTRUE);
  Mvd->SetGeometryFileName("Mvd-2.1_FullVersion.root"); // new mvd
  fRun->AddModule(Mvd);

  PndEmc *Emc = new PndEmc("EMC",kTRUE);
  Emc->SetGeometryVersion(15); 
  Emc->SetStorageOfData(kFALSE);
  fRun->AddModule(Emc);

//   FairModule *Support = new PndMagnet("Support");
//   Support->SetGeometryFileName("support_emc.geo");
//   fRun->AddModule(Support);
  
  PndMdt *Muo = new PndMdt("MDT",kTRUE);
  Muo->SetBarrel("fast");
  Muo->SetEndcap("fast");
  Muo->SetMuonFilter("fast");
  Muo->SetMdtMagnet(kTRUE);
  Muo->SetMdtMFIron(kTRUE);
  fRun->AddModule(Muo);

  FairDetector *Gem = new PndGemDetector("GEM", kTRUE);
  Gem->SetGeometryFileName("gem_3Stations.root");
  fRun->AddModule(Gem);

  PndDsk* Dsk = new PndDsk("DSK", kTRUE);
  Dsk->SetGeometryFileName("dsk.root");
  Dsk->SetStoreCerenkovs(kFALSE);
  Dsk->SetStoreTrackPoints(kFALSE);
  fRun->AddModule(Dsk); 

  PndDrc *Drc = new PndDrc("DIRC", kTRUE);
  Drc->SetRunCherenkov(kFALSE); // for fast sim Cherenkov -> kFALSE
  fRun->AddModule(Drc);
  
  // Create and Set Event Generator
  //-------------------------------

  FairPrimaryGenerator* primGen = new FairPrimaryGenerator();
  fRun->SetGenerator(primGen);

  // Pythia8
  PndPythia8Generator* P8gen = new PndPythia8Generator();
  P8gen->UseRandom3(); // TRandom1 or TRandom3 ?
  P8gen->SetParameters("PhaseSpace:pTHatMin = 0.001");
  P8gen->SetParameters("PhaseSpace:mHatMin = 0.001");
  P8gen->SetParameters("PhaseSpace:pTHatMinDiverge = 1.0000e-05");
  P8gen->SetParameters("PhaseSpace:minWidthBreitWigners = 0.00001");
  P8gen->SetParameters("HardQCD:all = on"); 
  P8gen->SetParameters("SoftQCD:all = off");
  P8gen->SetMom(momentum);  // pbar momentum
  primGen->AddGenerator(P8gen);

  //fRun->SetStoreTraj(kTRUE); // to store particle trajectories  

  // Create and Set Magnetic Field
  //-------------------------------
    fRun->SetBeamMom(momentum);

  PndMultiField *fField= new PndMultiField("FULL");
  fRun->SetField(fField);

  // EMC Hit producer
  //-------------------------------
  PndEmcHitProducer* emcHitProd = new PndEmcHitProducer();
  fRun->AddTask(emcHitProd);
   
  /**Initialize the session*/
  fRun->Init();
  //P8gen->Print();
 
  rtdb->setOutput(output);
  rtdb->saveOutput();
  rtdb->print();

  // Transport nEvents
  // -----------------
  fRun->Run(nEvents);

  timer.Stop();

  Double_t rtime = timer.RealTime();
  Double_t ctime = timer.CpuTime();
  printf("RealTime=%f seconds, CpuTime=%f seconds\n",rtime,ctime);

}