LEP2 is a project to double the beam energy of the LEP machine by introducing
superconducting accelerating cavities. The beam intensity was also increased
to match the decreasing collision rates for the higher energy (See the plot
above). This enabled to pair-produce the W particles,
electrically charged companions of the Z particles. At LEP2, the properties
of the W particles are studied with high accuracy, and the structure of the
elementary particles is investigated at such a small distance as 10-17cm.
Also, new particles, particularly the Higgs and the supersymmetric particles,
with masses as high as 110 GeV, are excluded. LEP2 finished its operation
at the end of year 2000.