LCIO Data Format


Linear Collider IO (LCIO) is a binary physics event data format originally developed for Linear Collider studies.  LCIO has C++ and Java APIs that can be used to read in LCIO files which typically have a .slcio extension.

LCIO compatible tools include the following:

  • SLIC - Geant4-based simulation tool
  • LCSim - physics reconstruction framework
  • JAS3 - graphical physics workbench application

In HPS, LCIO is used as the output format for MC simulation, using SLIC.  These events are read by HPS Java which creates reconstructed LCIO events via its use of LCSim.

The raw EVIO events from the DAQ are converted to LCIO using Java based builder classes.

The LCIO can also be converted to ROOT DST Data Format using the ROOT DST Maker.

Java API

LCSim includes an LCIO compatible API which models hits, digits, tracks and other physics objects.

The org.lcsim.lcio package contains the interfaces for this API.

Data Types

CalorimeterHitcalorimeter hit with raw and corrected energy, time and position
Clustercalorimeter cluster made of one or more CalorimeterHits
EventHeaderAPI for accessing event data by collection name
LCMetaDataobject collection metadata retrievable from EventHeader
GenericObjectcan represent and store data not modeled explicitly by LCIO
LCRelationlinks two objects together with an optional weight
MCParticleMonte Carlo particle information written by the simulation

tracker digit representing DAQ output

used for ECal data also in HPS



fully reconstructed particle hypothesis

may be composed of Clusters, Tracks or other ReconstructedParticles

SimCalorimeterHitcalorimeter hit with association to an MCParticle
SimTrackerHittracker hit with association to an MCParticle
Trackreconstructed track
TrackerHitgeneric tracker hit to be used by pattern recognition
TrackStaterepresents the state of a track at a certain location
Vertexreconstructed vertex


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