Reference

Glossary

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PODIO

Plain-Old-Data Input/Output — a toolkit for generating and managing event data models like EDM4eic. It reads a YAML description and generates the C++ and Python code used to read, write, and interface with the data.

EDM4eic

The Event Data Model for the EIC — the standardized set of data structures (tracks, clusters, associations, …) used throughout the ePIC software stack. Defined in a single YAML file, edm4eic.yaml.

EDM4hep

The Key4hep project’s event data model, also used in ePIC software (e.g. for MCParticles and common components like Vector3f).

Class

A data-model structure with members accessed via get/set-prefixed accessors (e.g. track.getMomentum()).

Component

A simple struct used inside classes (e.g. edm4hep::Vector3f); its members are accessed directly, without get/set prefixes (e.g. momentum.x).

Collection

A read-only container of data-model objects that can be written to and read from file (e.g. edm4eic::TrackCollection).

Frame

The PODIO container that holds and organizes all collections for one event (or, in streaming contexts, one timeframe).

Relation

A direct reference from one data-model object to one (OneToOneRelations) or many (OneToManyRelations) other objects, e.g. from a cluster to its calorimeter hits.

Association

A standalone object expressing an indirect, possibly absent connection between two objects, e.g. edm4eic::MCRecoParticleAssociation between a Monte-Carlo particle and its reconstructed counterpart.

Link

The successor of associations: a lightweight directional connection with fixed from/to/weight fields. Associations are being deprecated in favor of links.

E/p

The ratio of a matched cluster’s energy to the track’s momentum. Electrons and positrons deposit essentially all their energy in the electromagnetic calorimeter, so their tracks peak at \(E/p \approx 1\).