LCIO (Linear Collider I/O) is a persistency framework and event data model for linear collider detector studies. It is intended to be used in both simulation studies and analysis frameworks. Its light weight and portability makes it also suitable for use in detector R&D testbeam applications. It provides a C++ and a Java implementation with a common interface (API) - a Fortran interface to the C++ implementation also exists.

Using a common persistency format and event data model allows to easily share results and compare reconstruction algorithms. LCIO is used by almost all groups involved in linear collider detector studies and thus has become a de facto standard.

In particular it is used in the iLCSoft framework and in org.lcsim.


Release version v02-09

The current version of LCIO is available on Github. Please refer to the users manual on how to get and build LCIO.
Or browse the complete documetation here.
See versions.readme for release details.

older releases:


v02-04-02 v02-04-01 v02-04 v02-03-03 v02-03-02 v02-03-01 v02-03 v02-02 v02-01-02 v02-01 v02-00 v01-60 v01-51 New features in this release:
v01-12-02 New features in this release:
v01-11 New features in this release:
v01-10 New features in this release:
v01-09 New features in this release:

v01-08 New features in this release:

v01-07: New features in this release:

v01-06: This release allows to optionally store the momentum for SimTrackerHits and to skip any number of events when reading an LCIO file. Files are downward compatible with v01-05.

v01-05: This release adds new classes for raw tracker data: TrackerRawData, TrackerData and TrackerPulse. A number of improvements and bug fixes have been introduced. Some trivial changes might be necessary in user code as the return type of 4-momentum attributes of MCParticle and ReconstructedParticle have been changed to double. Files are downward compatible with v01-04.

v01-04: This release introduces collections that hold subsets of objects in other collections, transient and persistent. Multiple I/O streams are now also supported in C++. LCGenericObjects now also in Java. A small change in subclasses of LCGenericObject is needed (C++ only). Files are downward compatible with v01-03.

v01-03-01: A few bugs have been fixed in this release. No changes in the file format or API.

v01-03: The new release contains the reconstruction data model, support for user extension classes and relatioships between LCIO objects. Please refer to the manual for a detailed list of changes wrt. v01-00 and an introduction to the data model.

Due to restructuring of the software in some rare cases minor changes to user code might be necessary eventhough we tried to keep the API compatible with v01-00.

v01-00: Eventhough the file format has changed with respect to v00-08 old files can still be read with this new version of LCIO. From now on the file format of LCIO releases will be downward compatible (schema evolution). The API of MCParticle had to be changed in order to allow multiple parents (as used in the fragmentation process by most generators) and an additional simulator status word has been addded.

Developer and User Documentation

This section holds the latest developer and users documentation. If you are new to LCIO you can find a general introduction in the LC-Note LC-TOOL-2003-053 (pdf). The users manual is a good starting point for writing applications based on LCIO.

User Questions and Bug reports

There is a discussions forum on LCIO for developers at the Linear Collider Forum:
Users are welcome to post in that forum any questions or comments related to LCIO.

To report a bug in LCIO or request a new feature please go to and create a new issue.

Tools and Applications

Tools and Applications that support LCIO:


A collection of talks and minutes that document the design and development process of LCIO. These documents are not kept up to date, so please refer to the current user documentation for technical details.

Last modified: Wed Apr 20 11:51:39 2016

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