The Large Electron-Positron Collider (LEP) was one of the largest particle accelerators ever made. It was built at CERN, a multi-national center for research in nuclear and particle physics. LEP was a giant excavated ring with a circumference of 27 kilometers built in a tunnel under the border of Switzerland and France. It was used from 1989 until 2000. To date, LEP is the most powerful accelerator of leptons ever built.
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