Since the first collisions in 1989, LEP has provided a wealth of new data for the research teams to analyse. The earliest results contained vital information concerning how many different types of the lightweight neutrinos there are.
When the beams in LEP are tuned to the correct energy, the annihilations produce neutral particles (Z) - the neutral gauge bosons of the weak force. They decay instantly to particle-antiparticle pairs with a mass lower than the neutral particles mass. This includes neutrino-antineutrino pairs.
When the physicists compared the data from LEP with the predictions of the Standard Model, they found agreement only if there are three types of neutrino - no less, and importantly, no more. This indicates that we already know all the light neutrinos that exist. Moreover, the symmetry between the existing six types of quark and six types of lepton (including the three neutrinos) implies that there are no further particles of this kind. This result from LEP has provided dramatic confirmation of theories of the formation of elements in the big bang, as observations of the amount of primordial helium in the Universe today indicate that there should be no more than four types of neutrino. This is a perfect example of the relationship between particle physics and astronomy. Into the future with W bosons ...
LEP will continue to amass data until the end of the century, testing the Standard Model in precise detail. By 1997 the energy of the beams will have nearly doubled, as new accelerating cavities are installed. The new cavities are coated with niobium - a metal that becomes superconducting at low temperatures. This means that there is little electrical resistance, so that currents flow with far less loss of power, and more energy can be transferred to the particle beams.
With these higher beam energies, LEP will be able to study in detail the Wą particles - the charged partners of the Z. Because the Z is neutral, an electron and a positron, with no net charge, can annihilate to make a single Z, provided they have enough energy. However, the annihilations can make the charged W particles only in pairs - a W+ and a W- and this is what doubling the energy makes possible.
