fastsim::ParticleManager Class Reference

Manages GenParticles and Secondaries from interactions. More...

#include <ParticleManager.h>

Public Member Functions
unsigned	addEndVertex (const Particle *particle)
	Necessary to add an end vertex to a particle. More...
void	addSecondaries (const math::XYZTLorentzVector &vertexPosition, int motherSimTrackId, std::vector< std::unique_ptr< Particle > > &secondaries, const SimplifiedGeometry *layer=nullptr)
	Adds secondaries that are produced by any of the interactions (or particle decay) to the buffer. More...
const SimTrack	getSimTrack (unsigned i)
	Returns a given SimTrack. Needed for interfacing the code with the old calorimetry. More...
const SimVertex	getSimVertex (unsigned i)
	Returns the position of a given SimVertex. Needed for interfacing the code with the old calorimetry. More...
std::unique_ptr< Particle >	nextParticle (const RandomEngineAndDistribution &random)
	Returns the next particle that has to be propagated (secondary or genParticle). More...
	ParticleManager (const HepMC::GenEvent &genEvent, const HepPDT::ParticleDataTable &particleDataTable, double beamPipeRadius, double deltaRchargedMother, const ParticleFilter &particleFilter, std::vector< SimTrack > &simTracks, std::vector< SimVertex > &simVertices, bool useFastSimsDecayer)
	Constructor. More...
	~ParticleManager ()
	Default destructor. More...

Private Member Functions
unsigned	addSimTrack (const Particle *particle)
	Add a simTrack (simTrack contains some basic info about the particle, e.g. pdgId). More...
unsigned	addSimVertex (const math::XYZTLorentzVector &position, int motherIndex)
	Add a simVertex (simVertex contains information about the track it was produced). More...
void	exoticRelativesChecker (const HepMC::GenVertex *originVertex, int &hasExoticAssociation, int ngendepth)
std::unique_ptr< Particle >	nextGenParticle ()
	Returns next particle from the GenEvent that has to be propagated. More...

Private Attributes
const double	beamPipeRadius2_
	(Radius of the beampipe)^2 More...
const double	deltaRchargedMother_
	For FastSim (cheat) tracking: cut on the angle between a charged mother and charged daughter. More...
const HepMC::GenEvent *const	genEvent_
	The GenEvent. More...
const HepMC::GenEvent::particle_const_iterator	genParticleEnd_
	The last particle of the GenEvent. More...
int	genParticleIndex_
	Index of particle in the GenEvent (if it is a GenParticle) More...
HepMC::GenEvent::particle_const_iterator	genParticleIterator_
	Iterator to keep track on which GenParticles where already considered. More...
double	lengthUnitConversionFactor2_
	Convert pythia unis to cm^2 (FastSim standard) More...
double	lengthUnitConversionFactor_
	Convert pythia unis to cm (FastSim standard) More...
double	momentumUnitConversionFactor_
	Convert pythia units to GeV (FastSim standard) More...
std::vector< std::unique_ptr< Particle > >	particleBuffer_
	The vector of all secondaries that are not yet propagated in the event. More...
const HepPDT::ParticleDataTable *const	particleDataTable_
	Necessary to get information like lifetime and charge of a particle if unknown. More...
const ParticleFilter *const	particleFilter_
	(Kinematic) cuts on the particles that have to be propagated. More...
std::vector< SimTrack > *	simTracks_
	The generated SimTrack of this event. More...
std::vector< SimVertex > *	simVertices_
	The generated SimVertices of this event. More...
double	timeUnitConversionFactor_
	Convert pythia unis to ns (FastSim standard) More...
bool	useFastSimsDecayer_

Detailed Description

Manages GenParticles and Secondaries from interactions.

Manages which particle has to be propagated next, this includes GenParticles and secondaries from the interactions. Furthermore, checks if all necessary information is included with the GenParticles (charge, lifetime), otherwise reads information from HepPDT::ParticleDataTable. Also handles secondaries, including closestChargedDaughter algorithm which is used for FastSim (cheat) tracking: a charged daughter can continue the track of a charged mother, see addSecondaries(...).

Definition at line 36 of file ParticleManager.h.

Constructor & Destructor Documentation

ParticleManager()

fastsim::ParticleManager::ParticleManager	(	const HepMC::GenEvent &	genEvent,
		const HepPDT::ParticleDataTable &	particleDataTable,
		double	beamPipeRadius,
		double	deltaRchargedMother,
		const ParticleFilter &	particleFilter,
		std::vector< SimTrack > &	simTracks,
		std::vector< SimVertex > &	simVertices,
		bool	useFastSimsDecayer
	)

Constructor.

Parameters

genEvent	Get the GenEvent.
particleDataTable	Get information about particles, e.g. charge, lifetime.
beamPipeRadius	Radius of the beampipe.
deltaRchargedMother	For FastSim (cheat) tracking: cut on the angle between a charged mother and charged daughter.
particleFilter	Selects which particles have to be propagated.
simTracks	The SimTracks.
simVertices	The SimVertices.

Definition at line 17 of file ParticleManager.cc.

References addSimVertex(), genWeightsTable_cfi::genEvent, genEvent_, lengthUnitConversionFactor_, position, and timeUnitConversionFactor_.

    : genEvent_(&genEvent),
      genParticleIterator_(genEvent_->particles_begin()),
      genParticleEnd_(genEvent_->particles_end()),
      genParticleIndex_(1),
      particleDataTable_(&particleDataTable),
      beamPipeRadius2_(beamPipeRadius * beamPipeRadius),
      deltaRchargedMother_(deltaRchargedMother),
      particleFilter_(&particleFilter),
      simTracks_(&simTracks),
      simVertices_(&simVertices),
      useFastSimsDecayer_(useFastSimsDecayer)
      // prepare unit convsersions
      //  --------------------------------------------
      // |          |      hepmc               |  cms |
      //  --------------------------------------------
      // | length   | genEvent_->length_unit   |  cm  |
      // | momentum | genEvent_->momentum_unit |  GeV |
      // | time     | length unit (t*c)        |  ns  |
      //  --------------------------------------------
      ,
      momentumUnitConversionFactor_(conversion_factor(genEvent_->momentum_unit(), HepMC::Units::GEV)),
      lengthUnitConversionFactor_(conversion_factor(genEvent_->length_unit(), HepMC::Units::LengthUnit::CM)),
      lengthUnitConversionFactor2_(lengthUnitConversionFactor_ * lengthUnitConversionFactor_),
      timeUnitConversionFactor_(lengthUnitConversionFactor_ / fastsim::Constants::speedOfLight)

{
  // add the main vertex from the signal event to the simvertex collection
  if (genEvent.vertices_begin() != genEvent_->vertices_end()) {
    const HepMC::FourVector& position = (*genEvent.vertices_begin())->position();
    addSimVertex(math::XYZTLorentzVector(position.x() * lengthUnitConversionFactor_,
                                         position.y() * lengthUnitConversionFactor_,
                                         position.z() * lengthUnitConversionFactor_,
                                         position.t() * timeUnitConversionFactor_),
                 -1);
  }
}

~ParticleManager()

fastsim::ParticleManager::~ParticleManager

(

)

Default destructor.

Definition at line 62 of file ParticleManager.cc.

{}

Member Function Documentation

addEndVertex()

unsigned fastsim::ParticleManager::addEndVertex

(

const Particle *

particle

)

Necessary to add an end vertex to a particle.

Needed if particle is no longer propagated for some reason (e.g. remaining energy below threshold) and no secondaries where produced at that point.

Returns

Index of that vertex.

Definition at line 180 of file ParticleManager.cc.

References fastsim::Particle::position(), and fastsim::Particle::simTrackIndex().

                                                                             {
  return this->addSimVertex(particle->position(), particle->simTrackIndex());
}

addSecondaries()

void fastsim::ParticleManager::addSecondaries	(	const math::XYZTLorentzVector &	vertexPosition,
		int	motherSimTrackId,
		std::vector< std::unique_ptr< Particle > > &	secondaries,
		const SimplifiedGeometry *	layer = nullptr
	)

Adds secondaries that are produced by any of the interactions (or particle decay) to the buffer.

Also checks which charged daughter is closest to a charged mother (in deltaR) and assigns the same SimTrack ID.

Parameters

vertexPosition	The origin vertex (interaction or particle decay took place here).
motherSimTrackId	SimTrack ID of the mother particle, necessary for FastSim (cheat) tracking.
secondaries	All secondaries that where produced in a single particle decay or interaction.

Definition at line 121 of file ParticleManager.cc.

References muonTagProbeFilters_cff::distMin, heavyIonCSV_trainingSettings::idx, phase1PixelTopology::layer, and eostools::move().

Referenced by FastSimProducer::createFSimTrack().

                                                                               {
  // vertex must be within the accepted volume
  if (!particleFilter_->acceptsVtx(vertexPosition)) {
    return;
  }

  // no need to create vertex in case no particles are produced
  if (secondaries.empty()) {
    return;
  }

  // add simVertex
  unsigned simVertexIndex = addSimVertex(vertexPosition, parentSimTrackIndex);

  // closest charged daughter continues the track of the mother particle
  // simplified tracking algorithm for fastSim
  double distMin = 99999.;
  int idx = -1;
  int idxMin = -1;
  for (auto& secondary : secondaries) {
    idx++;
    if (secondary->getMotherDeltaR() != -1) {
      if (secondary->getMotherDeltaR() > deltaRchargedMother_) {
        // larger than max requirement on deltaR
        secondary->resetMother();
      } else {
        if (secondary->getMotherDeltaR() < distMin) {
          distMin = secondary->getMotherDeltaR();
          idxMin = idx;
        }
      }
    }
  }

  // add secondaries to buffer
  idx = -1;
  for (auto& secondary : secondaries) {
    idx++;
    if (idxMin != -1) {
      // reset all but the particle with the lowest deltaR (which is at idxMin)
      if (secondary->getMotherDeltaR() != -1 && idx != idxMin) {
        secondary->resetMother();
      }
    }

    // set origin vertex
    secondary->setSimVertexIndex(simVertexIndex);
    //
    if (layer) {
      secondary->setOnLayer(layer->isForward(), layer->index());
    }
    // ...and add particle to buffer
    particleBuffer_.push_back(std::move(secondary));
  }
}

addSimTrack()

unsigned fastsim::ParticleManager::addSimTrack ( const Particle *  particle )

private

Add a simTrack (simTrack contains some basic info about the particle, e.g. pdgId).

Add a simTrack for a given particle and assign an index for that track. This might also be the index of the track of the mother particle (FastSim cheat tracking).

Parameters

particle

Particle that produces that simTrack.

Returns

Index of that simTrack.

Definition at line 190 of file ParticleManager.cc.

References fastsim::Particle::genParticleIndex(), fastsim::Particle::momentum(), fastsim::Particle::pdgId(), and fastsim::Particle::simVertexIndex().

                                                                            {
  int simTrackIndex = simTracks_->size();
  simTracks_->emplace_back(
      particle->pdgId(), particle->momentum(), particle->simVertexIndex(), particle->genParticleIndex());
  simTracks_->back().setTrackId(simTrackIndex);
  return simTrackIndex;
}

addSimVertex()

unsigned fastsim::ParticleManager::addSimVertex ( const math::XYZTLorentzVector &  position, int  motherIndex  )

private

Add a simVertex (simVertex contains information about the track it was produced).

Add a origin vertex for any particle.

Parameters

position	Position of the vertex.
motherIndex	Index of the parent's simTrack.

Returns

Index of that simVertex.

Definition at line 184 of file ParticleManager.cc.

References position.

Referenced by ParticleManager().

                                                                                                            {
  int simVertexIndex = simVertices_->size();
  simVertices_->emplace_back(position.Vect(), position.T(), parentSimTrackIndex, simVertexIndex);
  return simVertexIndex;
}

exoticRelativesChecker()

void fastsim::ParticleManager::exoticRelativesChecker ( const HepMC::GenVertex *  originVertex, int &  hasExoticAssociation, int  ngendepth = 0  )

private

Definition at line 299 of file ParticleManager.cc.

References funct::abs(), GenParticle::GenParticle, and isExotic().

                                                                         {
  if (ngendepth > 99 || exoticRelativeId_ == -1 || isExotic(std::abs(exoticRelativeId_)))
    return;
  ngendepth += 1;
  std::vector<HepMC::GenParticle*>::const_iterator relativesIterator_ = originVertex->particles_in_const_begin();
  std::vector<HepMC::GenParticle*>::const_iterator relativesIteratorEnd_ = originVertex->particles_in_const_end();
  for (; relativesIterator_ != relativesIteratorEnd_; ++relativesIterator_) {
    const HepMC::GenParticle& genRelative = **relativesIterator_;
    if (isExotic(std::abs(genRelative.pdg_id()))) {
      exoticRelativeId_ = genRelative.pdg_id();
      if (ngendepth == 100)
        exoticRelativeId_ = -1;
      return;
    }
    const HepMC::GenVertex* vertex_ = genRelative.production_vertex();
    if (!vertex_)
      return;
    exoticRelativesChecker(vertex_, exoticRelativeId_, ngendepth);
  }
  return;
}

getSimTrack()

const SimTrack fastsim::ParticleManager::getSimTrack ( unsigned  i )

inline

Returns a given SimTrack. Needed for interfacing the code with the old calorimetry.

Definition at line 86 of file ParticleManager.h.

References mps_fire::i, and simTracks_.

Referenced by FastSimProducer::createFSimTrack().

{ return simTracks_->at(i); }

getSimVertex()

const SimVertex fastsim::ParticleManager::getSimVertex ( unsigned  i )

inline

Returns the position of a given SimVertex. Needed for interfacing the code with the old calorimetry.

Definition at line 83 of file ParticleManager.h.

References mps_fire::i, and simVertices_.

Referenced by FastSimProducer::createFSimTrack().

{ return simVertices_->at(i); }

nextGenParticle()

std::unique_ptr< fastsim::Particle > fastsim::ParticleManager::nextGenParticle ( )

private

Returns next particle from the GenEvent that has to be propagated.

Tries to get some basic information about the status of the particle from the GenEvent and does some first rejection cuts based on them.

Definition at line 198 of file ParticleManager.cc.

References funct::abs(), GenParticle::GenParticle, isExotic(), and fastsim::Constants::speedOfLight.

                                                                       {
  // only consider particles that start in the beam pipe and end outside the beam pipe
  // try to get the decay time from pythia
  // use hepmc units
  // make the link simtrack to simvertex
  // try not to change the simvertex structure

  // loop over gen particles
  for (; genParticleIterator_ != genParticleEnd_; ++genParticleIterator_, ++genParticleIndex_) {
    // some handy pointers and references
    const HepMC::GenParticle& particle = **genParticleIterator_;
    const HepMC::GenVertex* productionVertex = particle.production_vertex();
    const HepMC::GenVertex* endVertex = particle.end_vertex();

    // skip incoming particles
    if (!productionVertex) {
      continue;
    }
    if (std::abs(particle.pdg_id()) < 10 || std::abs(particle.pdg_id()) == 21) {
      continue;
    }
    
    // FastSim will not make hits out of particles that decay before reaching the beam pipe
    const bool decayedWithinBeamPipe =
        endVertex && endVertex->position().perp2() * lengthUnitConversionFactor2_ < beamPipeRadius2_;
        
    if (decayedWithinBeamPipe) {
      continue;
    }
    
        
    // boring particles (which do not descend from exotics) must be produced within the beampipe to leave hits
    int exoticRelativeId = 0;
    const bool producedWithinBeamPipe =
        productionVertex->position().perp2() * lengthUnitConversionFactor2_ < beamPipeRadius2_;
    if (!producedWithinBeamPipe  && useFastSimsDecayer_) {
      exoticRelativesChecker(productionVertex, exoticRelativeId, 0);
      if (!isExotic(exoticRelativeId)) {
        continue;
      }
    }
            
    if (!producedWithinBeamPipe && useFastSimsDecayer_) {
      exoticRelativesChecker(productionVertex, exoticRelativeId, 0);
      continue;
    }

    // SM particles that descend from exotics and cross the beam pipe radius should make hits but not be decayed
    if (producedWithinBeamPipe && !decayedWithinBeamPipe && useFastSimsDecayer_) {
      exoticRelativesChecker(productionVertex, exoticRelativeId, 0);
    }

    // make the particle
    std::unique_ptr<Particle> newParticle(
        new Particle(particle.pdg_id(),
                     math::XYZTLorentzVector(productionVertex->position().x() * lengthUnitConversionFactor_,
                                             productionVertex->position().y() * lengthUnitConversionFactor_,
                                             productionVertex->position().z() * lengthUnitConversionFactor_,
                                             productionVertex->position().t() * timeUnitConversionFactor_),
                     math::XYZTLorentzVector(particle.momentum().x() * momentumUnitConversionFactor_,
                                             particle.momentum().y() * momentumUnitConversionFactor_,
                                             particle.momentum().z() * momentumUnitConversionFactor_,
                                             particle.momentum().e() * momentumUnitConversionFactor_)));
    newParticle->setGenParticleIndex(genParticleIndex_);
    if (isExotic(exoticRelativeId)) {
      newParticle->setMotherPdgId(exoticRelativeId);
    }

    // try to get the life time of the particle from the genEvent
    if (endVertex) {
      double labFrameLifeTime =
          (endVertex->position().t() - productionVertex->position().t()) * timeUnitConversionFactor_;
      newParticle->setRemainingProperLifeTimeC(labFrameLifeTime / newParticle->gamma() *
                                               fastsim::Constants::speedOfLight);
    }
    
    // Find production vertex if it already exists. Otherwise create new vertex
    // Possible to recreate the whole GenEvent using SimTracks/SimVertices (see FBaseSimEvent::fill(..))
    bool foundVtx = false;
    for (const auto& simVtx : *simVertices_) {
      if (std::abs(simVtx.position().x() - newParticle->position().x()) < 1E-3 &&
          std::abs(simVtx.position().y() - newParticle->position().y()) < 1E-3 &&
          std::abs(simVtx.position().z() - newParticle->position().z()) < 1E-3) {
        newParticle->setSimVertexIndex(simVtx.vertexId());
        foundVtx = true;
        break;
      }
    }
    if (!foundVtx)
      newParticle->setSimVertexIndex(addSimVertex(newParticle->position(), -1));

    // iterator/index has to be increased in case of return (is not done by the loop then)
    ++genParticleIterator_;
    ++genParticleIndex_;
    // and return
    return newParticle;
  }

  return std::unique_ptr<Particle>();
}

nextParticle()

std::unique_ptr< fastsim::Particle > fastsim::ParticleManager::nextParticle

(

const RandomEngineAndDistribution &

random

)

Returns the next particle that has to be propagated (secondary or genParticle).

Main method of this class. At first consideres particles from the buffer (secondaries) if there are none, then the next GenParticle is considered. Only returns particles that pass the (kinetic) cuts of the ParticleFilter. Furthermore, uses the ParticleDataTable to ensure all necessary information about the particle is stored (lifetime, charge).

Returns

The next particle that has to be propagated.

See also

ParticleFilter

Definition at line 64 of file ParticleManager.cc.

References MillePedeFileConverter_cfg::e, RandomEngineAndDistribution::flatShoot(), dqm-mbProfile::log, eostools::move(), LHEGenericFilter_cfi::ParticleID, and ApeEstimator_cff::width.

                                                                                                             {
  std::unique_ptr<fastsim::Particle> particle;

  // retrieve particle from buffer
  if (!particleBuffer_.empty()) {
    particle = std::move(particleBuffer_.back());
    particleBuffer_.pop_back();
  }
  // or from genParticle list
  else {
    particle = nextGenParticle();
    if (!particle)
      return nullptr;
  }

  // if filter does not accept, skip particle
  if (!particleFilter_->accepts(*particle)) {
    return nextParticle(random);
  }

  // lifetime or charge of particle are not yet set
  if (!particle->remainingProperLifeTimeIsSet() || !particle->chargeIsSet()) {
    // retrieve the particle data
    const HepPDT::ParticleData* particleData = particleDataTable_->particle(HepPDT::ParticleID(particle->pdgId()));
    if (!particleData) {
      // in very few events the Decayer (pythia) produces high mass resonances that are for some reason not present in the table (even though they should technically be)
      // they have short lifetimes, so decay them right away (charge and lifetime cannot be taken from table)
      particle->setRemainingProperLifeTimeC(0.);
      particle->setCharge(0.);
    }

    // set lifetime
    if (!particle->remainingProperLifeTimeIsSet()) {
      // The lifetime is 0. in the Pythia Particle Data Table! Calculate from width instead (ct=hbar/width).
      // ct=particleData->lifetime().value();
      double width = particleData->totalWidth().value();
      if (width > 1.0e-35) {
        particle->setRemainingProperLifeTimeC(-log(random.flatShoot()) * 6.582119e-25 / width / 10.);  // ct in cm
      } else {
        particle->setStable();
      }
    }

    // set charge
    if (!particle->chargeIsSet()) {
      particle->setCharge(particleData->charge());
    }
  }

  // add corresponding simTrack to simTrack collection
  unsigned simTrackIndex = addSimTrack(particle.get());
  particle->setSimTrackIndex(simTrackIndex);

  // and return
  return particle;
}

Member Data Documentation

beamPipeRadius2_

const double fastsim::ParticleManager::beamPipeRadius2_

private

(Radius of the beampipe)^2

Definition at line 130 of file ParticleManager.h.

deltaRchargedMother_

const double fastsim::ParticleManager::deltaRchargedMother_

private

For FastSim (cheat) tracking: cut on the angle between a charged mother and charged daughter.

Definition at line 132 of file ParticleManager.h.

genEvent_

const HepMC::GenEvent* const fastsim::ParticleManager::genEvent_

private

The GenEvent.

Definition at line 123 of file ParticleManager.h.

Referenced by ParticleManager().

genParticleEnd_

const HepMC::GenEvent::particle_const_iterator fastsim::ParticleManager::genParticleEnd_

private

The last particle of the GenEvent.

Definition at line 126 of file ParticleManager.h.

genParticleIndex_

int fastsim::ParticleManager::genParticleIndex_

private

Index of particle in the GenEvent (if it is a GenParticle)

Definition at line 127 of file ParticleManager.h.

genParticleIterator_

HepMC::GenEvent::particle_const_iterator fastsim::ParticleManager::genParticleIterator_

private

Iterator to keep track on which GenParticles where already considered.

Definition at line 125 of file ParticleManager.h.

lengthUnitConversionFactor2_

double fastsim::ParticleManager::lengthUnitConversionFactor2_

private

Convert pythia unis to cm^2 (FastSim standard)

Definition at line 139 of file ParticleManager.h.

lengthUnitConversionFactor_

double fastsim::ParticleManager::lengthUnitConversionFactor_

private

Convert pythia unis to cm (FastSim standard)

Definition at line 138 of file ParticleManager.h.

Referenced by ParticleManager().

momentumUnitConversionFactor_

double fastsim::ParticleManager::momentumUnitConversionFactor_

private

Convert pythia units to GeV (FastSim standard)

Definition at line 137 of file ParticleManager.h.

particleBuffer_

std::vector<std::unique_ptr<Particle> > fastsim::ParticleManager::particleBuffer_

private

The vector of all secondaries that are not yet propagated in the event.

Definition at line 142 of file ParticleManager.h.

particleDataTable_

const HepPDT::ParticleDataTable* const fastsim::ParticleManager::particleDataTable_

private

Necessary to get information like lifetime and charge of a particle if unknown.

Definition at line 129 of file ParticleManager.h.

particleFilter_

const ParticleFilter* const fastsim::ParticleManager::particleFilter_

private

(Kinematic) cuts on the particles that have to be propagated.

Definition at line 133 of file ParticleManager.h.

simTracks_

std::vector<SimTrack>* fastsim::ParticleManager::simTracks_

private

The generated SimTrack of this event.

Definition at line 134 of file ParticleManager.h.

Referenced by getSimTrack().

simVertices_

std::vector<SimVertex>* fastsim::ParticleManager::simVertices_

private

The generated SimVertices of this event.

Definition at line 135 of file ParticleManager.h.

Referenced by getSimVertex().

timeUnitConversionFactor_

double fastsim::ParticleManager::timeUnitConversionFactor_

private

Convert pythia unis to ns (FastSim standard)

Definition at line 140 of file ParticleManager.h.

Referenced by ParticleManager().

useFastSimsDecayer_

bool fastsim::ParticleManager::useFastSimsDecayer_

private

Definition at line 136 of file ParticleManager.h.