LEP breaks all records

4 November 1998

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The world's largest particle accelerator, the Large Electron Positron collider (LEP) at the European Laboratory for Particle Physics, CERN, has had a record-breaking year in 1998. By the time it stopped running for 1998, on 2 November, the machine's performance had exceeded all expectations. This graph basically indicates how the total amount of beam - more technically, the integrated luminosity - delivered to the experiments at LEP has risen during the run, and it shows how running in 1998 has improved on previous years. Luminosity in a particle collider such as LEP indicates how intense the beams are before they collide, and it is usually given as a number per square centimetre per second. Adding up (integrating) the luminosity over the number of seconds for the whole run, gives the total luminosity as a number per square centimetre, or in this case per picobarn (Pb-1), where a picobarn is 10-36 cm2. The aim at LEP for 1998 was to reach a total luminosity of 150 Pb-1, but this target had been reached by 5 October, four weeks before the end of the run! This was good news for the four experiments at LEP, which are studying the production of pairs of W particles, the carriers of the weak force.

Credit: CERN

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