First events at LEP's final frontier
19 April 2000
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The Large Electron Positron (LEP) collider at CERN,
Europe's laboratory for particle physics, has begun its final assault
on the high energy frontier, with events such as this at a total energy
of 205 GeV.
The 27-km circumference machine is due to shut down in October 2000,
and will then be dismantled to make way for the Large Hadron Collider
(LHC), which is to be built in the same tunnel. This image shows a
computer reconstruction of the tracks produced by the decays of the
first pair of W particles (carriers of the weak force) captured by a
detector at LEP in 2000. The W+ and W- were created when an electron
and a positron annihilated at the centre of the DELPHI detector.
Both W particles have decayed into a quark and an antiquark.
These do not emerge in the detector as single particles, but instead
each creates a "jet"
of particles, so making four jets in all. The general directions of
each jet of particles are indicated by the large arrows. The yellow
cylinder outlines the general structure of the main tracking part of the DELPHI detector.
Live events from OPAL, another of the four detectors at LEP.
Credit: CERN / DELPHI