A collision between an electron and a positron at 140 GeV. The positron emits a photon and then interacts with the electron producing a Z particle. This decays into a quark and antiquark which in turn produces a jet of particles. It was observed in the DELPHI detector. Detectors are used to measure properties of particles. Some measure the tracks left behind by particles and others measure energy. Founded in 1954, CERN is the world's leading particle physics research laboratory, and one of Europe's first joint ventures.
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