PythiaDecays Class Reference

#include <PythiaDecays.h>

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

Private Attributes
std::unique_ptr< Pythia8::Pythia >	decayer
gen::P8RndmEnginePtr	p8RndmEngine
DaughterParticleList	theList

Detailed Description

Definition at line 29 of file PythiaDecays.h.

Constructor & Destructor Documentation

PythiaDecays()

PythiaDecays::PythiaDecays

(

)

Definition at line 12 of file PythiaDecays.cc.

References decayer, and p8RndmEngine.

                           {
  // inspired by method Pythia8Hadronizer::residualDecay() in GeneratorInterface/Pythia8Interface/src/Py8GunBase.cc
  decayer = std::make_unique<Pythia8::Pythia>();
  p8RndmEngine = std::make_shared<gen::P8RndmEngine>();
  decayer->setRndmEnginePtr(p8RndmEngine);
  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);
  }
}

~PythiaDecays()

PythiaDecays::~PythiaDecays

(

)

Definition at line 32 of file PythiaDecays.cc.

{}

Member Function Documentation

particleDaughters()

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

Definition at line 34 of file PythiaDecays.cc.

References decayer, makeParticle(), RawParticle::mass(), RawParticle::momentum(), p8RndmEngine, BaseParticlePropagator::particle(), ParticlePropagator::particleDataTable(), RawParticle::pid(), RawParticle::T(), theList, RawParticle::X(), RawParticle::Y(), and RawParticle::Z().

Referenced by TrajectoryManager::updateWithDaughters().

                                                                                          {
  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;
}

Member Data Documentation

decayer

std::unique_ptr<Pythia8::Pythia> PythiaDecays::decayer

private

Definition at line 37 of file PythiaDecays.h.

Referenced by particleDaughters(), and PythiaDecays().

p8RndmEngine

gen::P8RndmEnginePtr PythiaDecays::p8RndmEngine

private

Definition at line 38 of file PythiaDecays.h.

Referenced by particleDaughters(), and PythiaDecays().

theList

DaughterParticleList PythiaDecays::theList

private

Definition at line 36 of file PythiaDecays.h.

Referenced by particleDaughters().