DELPHI was one of four large detectors on the Large Electron-Positron collider (LEP). It took 7 years to design and build, and it started up in 1989. In December 2000, DELPHI stopped taking data and was dismantled to leave room for the construction of the Large Hadron Collider in the LEP tunnel.

DELPHI consisted of a central cylinder filled with subdetectors, with two end-caps. It was 10 meters in length and diameter, and weighed 3500 tons. The detector consisted of 20 subdetectors. A large superconducting magnet sat between an electromagnetic calorimeter (for tracking electrons) and a hadronic calorimeter (to detect hadrons). The magnet generated a field to deflect charged particles so their charge and momenta could be measured.

The collaboration running the detector consisted of about 550 physicists from 56 participating universities and institutes in 22 countries.

Computing Environment

DELPHI binaries are distributed via CVMFS via /cvmfs/ Several Linux distributions are supported. For the time being, only 32bit is supported, 64bit support is experimental and has not been validated. The binaries can be used directly from CVMFS, or via a virtual machine. DELPHI and OPAL can share the same virtual machine image using CernVM. The virtual machine environment can be created by running CernVM with the cloud-init user data file for delphi: delphi.yaml. It will be easiest to run the CernVM on the CERN OpenStack, for more information consider these websites: and Some instructions for the use of the cloud-init user data is embedded in the file, look though the file.

The virtual machine configured by the cloud-init user data lets you connect to EOS to access the experiment data. You have to be a member of the DELPHI group (Unix group XX) though, access to the data is protected via Kerberos. You need to run the VM in a context where it can access these services.