simcore::hepmc::HepMCEvent Class Reference

Wrapper for HepMC3::GenEvent with convenience methods. More...

#include <HepMCEvent.h>

Public Member Functions
	HepMCEvent (std::shared_ptr< HepMC3::GenEvent > event)
	Class constructor.
virtual	~HepMCEvent ()=default
	Class destructor.
int	getNumParticles () const
	Get the number of particles in the event.
double	getEventWeight () const
	Get the event weight.
const double *	getVertex () const
	Get the vertex location (in mm, as expected by Geant4).
double	getVertexTime () const
	Get the vertex time (in ns, as expected by Geant4).
const std::vector< std::unique_ptr< HepMCParticle > > &	getParticles () const
	Get the list of final state particles in the event.
std::shared_ptr< HepMC3::GenEvent >	getGenEvent () const
	Get the underlying HepMC3 GenEvent.

Private Member Functions
void	extractParticles () const
	Extract final state particles from the HepMC event.

Private Attributes
std::shared_ptr< HepMC3::GenEvent >	event_
	The underlying HepMC3 GenEvent.
double	vtx_ [3]
	Vertex location (in mm)
double	vtxt_ {0.}
	Vertex time (in ns)
std::vector< std::unique_ptr< HepMCParticle > >	particles_
	The list of final state particles to be tracked.
bool	particles_extracted_ {false}
	Flag to indicate if particles have been extracted.

Detailed Description

Wrapper for HepMC3::GenEvent with convenience methods.

Note

Detailed information on the HepMC3 format is provided here: HepMC3: A modernized Monte Carlo event structure library.

Definition at line 37 of file HepMCEvent.h.

Constructor & Destructor Documentation

HepMCEvent()

simcore::hepmc::HepMCEvent::HepMCEvent

(

std::shared_ptr< HepMC3::GenEvent >

event

)

Class constructor.

Parameters

event

Shared pointer to HepMC3 GenEvent

Definition at line 6 of file HepMCEvent.cxx.

    : event_(event) {
  if (!event_) {
    EXCEPTION_RAISE("NullEvent",
                    "Attempted to create HepMCEvent with null GenEvent");
  }
 
  // Extract vertex information from the signal process vertex
  // or the first vertex if no signal process is defined
  std::shared_ptr<HepMC3::GenVertex> vertex;
 
  // Try to get the signal process vertex first
  if (event_->vertices().size() > 0) {
    vertex = event_->vertices()[0];
  }
 
  if (vertex) {
    // HepMC3 uses mm for length and mm/c for time by default
    const HepMC3::FourVector& pos = vertex->position();
    vtx_[0] = pos.x();  // mm
    vtx_[1] = pos.y();  // mm
    vtx_[2] = pos.z();  // mm
    vtxt_ = pos.t();    // mm/c, needs conversion to ns for Geant4
 
    // Convert time from mm/c to ns: t[ns] = t[mm/c] / c[mm/ns]
    // c = 299.792458 mm/ns
    vtxt_ = vtxt_ / 299.792458;
  } else {
    vtx_[0] = 0.0;
    vtx_[1] = 0.0;
    vtx_[2] = 0.0;
    vtxt_ = 0.0;
  }
}

References event_, vtx_, and vtxt_.

Member Function Documentation

extractParticles()

void simcore::hepmc::HepMCEvent::extractParticles ( ) const

private

Extract final state particles from the HepMC event.

Definition at line 70 of file HepMCEvent.cxx.

                                        {
  particles_.clear();
 
  // Get all particles from the event
  for (const auto& particle : event_->particles()) {
    // In HepMC3, status code 1 typically means final state particle
    // Status codes vary by generator, but generally:
    // status = 1: final state particle
    // status = 2: intermediate/decayed particle
    // status > 2: generator-specific codes
 
    // We include particles with status code 1 (final state)
    if (particle->status() == 1) {
      particles_.push_back(std::make_unique<HepMCParticle>(particle));
    }
  }
 
  particles_extracted_ = true;
}

References event_, particles_, and particles_extracted_.

Referenced by getNumParticles(), and getParticles().

getEventWeight()

double simcore::hepmc::HepMCEvent::getEventWeight

(

)

const

Get the event weight.

Returns

The event weight.

Definition at line 48 of file HepMCEvent.cxx.

                                        {
  // HepMC3 events can have multiple weights, we take the first one
  const std::vector<double>& weights = event_->weights();
  return weights.empty() ? 1.0 : weights[0];
}

References event_.

getGenEvent()

std::shared_ptr< HepMC3::GenEvent > simcore::hepmc::HepMCEvent::getGenEvent

(

)

const

Get the underlying HepMC3 GenEvent.

Returns

Shared pointer to the HepMC3 GenEvent

Definition at line 66 of file HepMCEvent.cxx.

                                                            {
  return event_;
}

References event_.

getNumParticles()

int simcore::hepmc::HepMCEvent::getNumParticles

(

)

const

Get the number of particles in the event.

Returns

The number of particles in event.

Definition at line 41 of file HepMCEvent.cxx.

                                      {
  if (!particles_extracted_) {
    extractParticles();
  }
  return particles_.size();
}

References extractParticles(), particles_, and particles_extracted_.

getParticles()

const std::vector< std::unique_ptr< HepMCParticle > > & simcore::hepmc::HepMCEvent::getParticles

(

)

const

Get the list of final state particles in the event.

These are particles that should be tracked by Geant4.

Returns

The list of final state particles in the event.

Definition at line 58 of file HepMCEvent.cxx.

          {
  if (!particles_extracted_) {
    extractParticles();
  }
  return particles_;
}

References extractParticles(), particles_, and particles_extracted_.

getVertex()

const double * simcore::hepmc::HepMCEvent::getVertex

(

)

const

Get the vertex location (in mm, as expected by Geant4).

Returns

Array double[3] with x, y, z ordering

Definition at line 54 of file HepMCEvent.cxx.

{ return vtx_; }

References vtx_.

getVertexTime()

double simcore::hepmc::HepMCEvent::getVertexTime

(

)

const

Get the vertex time (in ns, as expected by Geant4).

Returns

time of primary vertex.

Definition at line 56 of file HepMCEvent.cxx.

{ return vtxt_; }

References vtxt_.

Member Data Documentation

event_

std::shared_ptr<HepMC3::GenEvent> simcore::hepmc::HepMCEvent::event_

private

The underlying HepMC3 GenEvent.

Definition at line 91 of file HepMCEvent.h.

Referenced by extractParticles(), getEventWeight(), getGenEvent(), and HepMCEvent().

particles_

std::vector<std::unique_ptr<HepMCParticle> > simcore::hepmc::HepMCEvent::particles_

mutableprivate

The list of final state particles to be tracked.

Definition at line 106 of file HepMCEvent.h.

Referenced by extractParticles(), getNumParticles(), and getParticles().

particles_extracted_

bool simcore::hepmc::HepMCEvent::particles_extracted_ {false}

mutableprivate

Flag to indicate if particles have been extracted.

Definition at line 111 of file HepMCEvent.h.

{false};

Referenced by extractParticles(), getNumParticles(), and getParticles().

vtx_

double simcore::hepmc::HepMCEvent::vtx_[3]

mutableprivate

Vertex location (in mm)

Definition at line 96 of file HepMCEvent.h.

Referenced by getVertex(), and HepMCEvent().

vtxt_

double simcore::hepmc::HepMCEvent::vtxt_ {0.}

mutableprivate

Vertex time (in ns)

Definition at line 101 of file HepMCEvent.h.

{0.};

Referenced by getVertexTime(), and HepMCEvent().

---

The documentation for this class was generated from the following files:

• SimCore/include/SimCore/HepMC/HepMCEvent.h
• SimCore/src/SimCore/HepMC/HepMCEvent.cxx