Pairs of W particles as LEP starts up for 1999
19 May 1999
The Large Electron Positron Collider (LEP) has begun its penultimate run at the European Laboratory for Particle Physics, CERN, Geneva. Beginning its 11th year of operation, LEP is already running at its highest energy so far - a total of 192 GeV (gigaelectronvolts) - and should eventually reach 200 GeV, twice its original energy. This image shows the decay of two W particles produced at 192 GeV at the centre of the DELPHI detector at LEP. Concentric layers of the detector surround the collider's beam pipe, which passes through the centre of this image, perpendicular to the screen. The W particles - carriers of the weak force - have both decayed to two quarks. Each of the four resulting quarks has generated a distinct "jet" of charged particles that shoot off through the layers of the detector. Next year will see LEP's last run, after which it will be dismantled to make way for a proton collider - the Large Hadron Collider (LHC) - which will occupy the same tunnel.
Examples of WW production at 192 GeV have also been seen in the other detectors at LEP. See the latest events from ALEPH; look here at live events from OPAL; and keep a watch here for events from L3. Also check here for the current status of LEP. (The DELPHI experiment detected the first W pair at LEP in 1996.)
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