#include <PythiaDecays.h>

Public Member Functions
const DaughterParticleList &	particleDaughters (ParticlePropagator &particle, CLHEP::HepRandomEngine *)

	PythiaDecays ()

	~PythiaDecays ()

Private Attributes
std::unique_ptr< Pythia8::Pythia >	decayer

std::unique_ptr< gen::P8RndmEngine >	p8RndmEngine

DaughterParticleList	theList

Detailed Description

Definition at line 28 of file PythiaDecays.h.

Constructor & Destructor Documentation

◆ PythiaDecays()

PythiaDecays::PythiaDecays ( )

Definition at line 12 of file PythiaDecays.cc.

                            {
   // inspired by method Pythia8Hadronizer::residualDecay() in GeneratorInterface/Pythia8Interface/src/Py8GunBase.cc
   decayer = std::make_unique<Pythia8::Pythia>();
   p8RndmEngine = std::make_unique<gen::P8RndmEngine>();
   decayer->setRndmEnginePtr(p8RndmEngine.get());
   decayer->settings.flag("ProcessLevel:all", false);
   decayer->settings.flag("PartonLevel:FSRinResonances", false);
   decayer->settings.flag("ProcessLevel:resonanceDecays", false);
   decayer->init();
  
   // forbid all decays
   // (decays are allowed selectively in the particleDaughters function)
   Pythia8::ParticleData& pdt = decayer->particleData;
   int pid = 1;
   while (pdt.nextId(pid) > pid) {
     pid = pdt.nextId(pid);
     pdt.mayDecay(pid, false);
   }
 }

References decayer, and p8RndmEngine.

◆ ~PythiaDecays()

PythiaDecays::~PythiaDecays ( )

Definition at line 32 of file PythiaDecays.cc.

32 {}

Member Function Documentation

◆ particleDaughters()

const DaughterParticleList & PythiaDecays::particleDaughters	(	ParticlePropagator &	particle,
		CLHEP::HepRandomEngine *	engine
	)

Definition at line 34 of file PythiaDecays.cc.

                                                                                           {
   edm::RandomEngineSentry<gen::P8RndmEngine> sentry(p8RndmEngine.get(), engine);
  
   theList.clear();
  
   // inspired by method Pythia8Hadronizer::residualDecay() in GeneratorInterface/Pythia8Interface/src/Py8GunBase.cc
   int pid = particle.particle().pid();
   decayer->event.reset();
   Pythia8::Particle py8part(pid,
                             93,
                             0,
                             0,
                             0,
                             0,
                             0,
                             0,
                             particle.particle().momentum().x(),  // note: momentum().x() and Px() are the same
                             particle.particle().momentum().y(),
                             particle.particle().momentum().z(),
                             particle.particle().momentum().t(),
                             particle.particle().mass());
   py8part.vProd(particle.particle().X(), particle.particle().Y(), particle.particle().Z(), particle.particle().T());
   decayer->event.append(py8part);
  
   int nentries_before = decayer->event.size();
   decayer->particleData.mayDecay(pid,
                                  true);  // switch on the decay of this and only this particle (avoid double decays)
   decayer->next();                       // do the decay
   decayer->particleData.mayDecay(pid, false);  // switch it off again
   int nentries_after = decayer->event.size();
   if (nentries_after <= nentries_before)
     return theList;
  
   theList.reserve(nentries_after - nentries_before);
  
   for (int ipart = nentries_before; ipart < nentries_after; ipart++) {
     Pythia8::Particle& py8daughter = decayer->event[ipart];
     theList
         .emplace_back(makeParticle(
             particle.particleDataTable(),
             py8daughter.id(),
             XYZTLorentzVector(py8daughter.px(), py8daughter.py(), py8daughter.pz(), py8daughter.e()),
             XYZTLorentzVector(py8daughter.xProd(), py8daughter.yProd(), py8daughter.zProd(), py8daughter.tProd())))
         .setMass(py8daughter.m());
   }
  
   return theList;
 }