The legacy of CERN’s first big precision machine

A particle track detected by the DELPHI detector at the Large Electron-Positron (LEP): it reveals a Z particle decaying into a quark-antiquark pair.
A particle track detected by the DELPHI detector at the Large Electron-Positron (LEP): it reveals a Z particle decaying into a quark-antiquark pair.

The Large Electron-Positron (LEP) collider is decommissioned in November. Over its 11 years of operation, from 1989 to 2000, it has produced 17 million Z bosons, uncharged mediators of the weak force, and approximately 40 000 pairs of W bosons, charged mediators of the weak force. The precision measurements conducted at LEP have provided stringent tests of the Standard Model of particle physics, confirming the existence of three generations of fundamental particles and placing the Standard Model on solid experimental ground.


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