LEP's prompt abundance

Abstract

Never have so many physicists gained so much so quickly from one machine. On 14 July a particle beam circulated around CERN's LEP ring for the first time. On 13 August, circulating beams of electrons and positrons were brought into collision for the first time, and the first Z0 particles were produced and detected within a few minutes. The first physics run of the machine started on 18 September, and was completed on 9 October. On 13 October the first physics results of the four LEP experimental collaborations were presented to a packed audience at CERN (Physics World November p6). The new measurements that were reported of the mass and ‘decay width’ of the Z0 and of the number of neutrino types are important not only in themselves but also for their implications for unseen entities such as the top quark, the Higgs boson and particles whose existence is predicted by theories of supersymmetry.