PythiaDecays.cc

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// HepMC Headers
#include "HepMC/PythiaWrapper6_4.h"

// Pythia6 framework integration service Headers
#include "GeneratorInterface/Pythia6Interface/interface/Pythia6Service.h"

// FAMOS Headers
#include "FastSimulation/ParticlePropagator/interface/ParticlePropagator.h"
#include "FastSimulation/ParticleDecay/interface/PythiaDecays.h"
#include "FastSimulation/ParticleDecay/interface/Pythia6jets.h"
#include "FastSimulation/ParticleDecay/interface/RandomP8.h"


// Needed for Pythia6 
#define PYTHIA6PYDECY pythia6pydecy_

extern "C" {
  void PYTHIA6PYDECY(int *ip);
}

PythiaDecays::PythiaDecays(std::string program)
{
  program_=program;
  if (program_ == "pythia6") {
    pyjets = new Pythia6jets();
    pyservice = new gen::Pythia6Service();
    // The PYTHIA decay tables will be initialized later 
  } else if (program_ == "pythia8") {
    pythia.reset(new Pythia8::Pythia);
    decayer.reset(new Pythia8::Pythia);

    RandomP8* RP8 = new RandomP8();
    pythia->setRndmEnginePtr(RP8);
    decayer->setRndmEnginePtr(RP8);
  } else {
    std::cout << "WARNING: you are requesting an option which is not available in PythiaDecays::PythiaDecays " << std::endl;
  }

}

PythiaDecays::~PythiaDecays() {
  if (program_ == "pythia6") {
    delete pyjets;
    delete pyservice;
  }
}

const DaughterParticleList&
PythiaDecays::particleDaughtersPy8(ParticlePropagator& particle)
{

  theList.clear();

  /*
  std::cout << "###" << std::endl;
  std::cout << "particle.PDGname() == " << particle.PDGname() << std::endl; 
  std::cout << "particle.status() == " << particle.status() << std::endl;
  std::cout << "particle.pid() == " << particle.pid() << std::endl;
  std::cout << "particle.momentum().x() == " << particle.momentum().x() << std::endl;
  std::cout << "particle.Px() == " << particle.Px() << std::endl;
  std::cout << "particle.X() == " << particle.X() << std::endl;
  std::cout << "particle.mass() == " << particle.mass() << std::endl;
  std::cout << "particle.PDGmass() == " << particle.PDGmass() << std::endl;
  std::cout << "particle.PDGcTau() == " << particle.PDGcTau() << std::endl;
  std::cout << "(decayer->particleData).tau0( particle.pid() ) == " << (decayer->particleData).tau0( particle.pid() ) << std::endl;
  */

  // inspired by method Pythia8Hadronizer::residualDecay() in GeneratorInterface/Pythia8Interface/src/Pythia8Hadronizer.cc
  decayer->event.reset();
  Pythia8::Particle py8part(  particle.pid(), 93, 0, 0, 0, 0, 0, 0,
             particle.momentum().x(), // note: momentum().x() and Px() are the same
             particle.momentum().y(),
             particle.momentum().z(),
             particle.momentum().t(),
             particle.mass() );
  py8part.vProd( particle.X(), particle.Y(), 
         particle.Z(), particle.T() );
  py8part.tau( (decayer->particleData).tau0( particle.pid() ) );
  decayer->event.append( py8part );

  int nentries = decayer->event.size();
  if ( !decayer->event[nentries-1].mayDecay() ) return theList;
  decayer->next();
  int nentries1 = decayer->event.size();
  if ( nentries1 <= nentries ) return theList; //same number of particles, no decays...
  Pythia8::Particle& py8daughter = decayer->event[nentries]; // the 1st daughter // DO I NEED THIS LINE?

  theList.resize(nentries,RawParticle());

  for ( int ipart=nentries+1; ipart<nentries1; ipart++ )
    {
      py8daughter = decayer->event[ipart];
      theList[ipart-nentries-1].SetXYZT( py8daughter.px(), py8daughter.py(), py8daughter.pz(), py8daughter.e() );
      theList[ipart-nentries-1].setVertex( py8daughter.xProd(),
                       py8daughter.yProd(),
                       py8daughter.zProd(),
                       py8daughter.tProd() );
      theList[ipart-nentries-1].setID( py8daughter.id() );
      theList[ipart-nentries-1].setMass( py8daughter.m() );
    }

  return theList;
}

const DaughterParticleList&
PythiaDecays::particleDaughtersPy6(ParticlePropagator& particle)
{
  gen::Pythia6Service::InstanceWrapper guard(pyservice); // grab Py6 context

  //  Pythia6jets pyjets;
  int ip;

  pyjets->k(1,1) = 1;
  pyjets->k(1,2) = particle.pid();
  pyjets->p(1,1) = particle.Px();
  pyjets->p(1,2) = particle.Py();
  pyjets->p(1,3) = particle.Pz();
  pyjets->p(1,4) = std::max(particle.mass(),particle.e());
  pyjets->p(1,5) = particle.mass();
  pyjets->v(1,1) = particle.X();
  pyjets->v(1,2) = particle.Y();
  pyjets->v(1,3) = particle.Z();
  pyjets->v(1,4) = particle.T();
  pyjets->n() = 1;
  
  ip = 1;
  PYTHIA6PYDECY(&ip);

  // Fill the list of daughters
  theList.clear();
  if ( pyjets->n()==1 ) return theList; 

  theList.resize(pyjets->n()-1,RawParticle());

  for (int i=2;i<=pyjets->n();++i) {
    
    theList[i-2].SetXYZT(pyjets->p(i,1),pyjets->p(i,2),
             pyjets->p(i,3),pyjets->p(i,4)); 
    theList[i-2].setVertex(pyjets->v(i,1),pyjets->v(i,2),
               pyjets->v(i,3),pyjets->v(i,4));
    theList[i-2].setID(pyjets->k(i,2));
    theList[i-2].setMass(pyjets->p(i,5));

  }

  return theList;
  
}