OPAL was one of the major particle physics experiments at CERN. OPAL studied particles and their interactions by collecting and analyzing electron-positron collision events at LEP, the Large Electron-Positron collider.

The OPAL experiment and the LEP collider started operation in August 1989. Data taking finally ended on November 2, 2000.

Computing Environment

OPAL binaries are distributed via CVMFS via /cvmfs/opal.cern.ch. Several Linux distributions are supported. The binaries can be used directly from CVMFS, for example from lxplus.cern.ch, or via a virtual machine. The environment can also be run directly from any desktop which has both /cvmfs/opal.cern.ch and /eos/experiment/opal mounted, sourcing the environment from /cvmfs/opal.cern.ch/env/group_rc.sh or /cvmfs/opal.cern.ch/env/group_rc.sh. The OPAL data will become available on https://opendata.cern during 2026.