The scientists were looking for collisions that can be written in the following way, known as Higgs events:

e+ + e- -> Z + H -> Z + b + anti-b.
The Z particle has many different decay possibilities, and different groups of scientists were looking for collisions with different decays. For example, the group of scientists from Stockholm was specialized in looking for Higgs collisions where the Z particle decayed into two neutrinos.

The Stockholm group was therefore looking for collisions with two b-quarks and two neutrinos. The two quarks will give rise to two jets of particles, while the two neutrinos cannot be detected since they only interact weakly. In such a collision there will be less energy than expected, since the neutrinos carry away some energy that will not be detected.

At the end of the data taking at LEP, the scientists thought they saw some traces of the Higgs particle, but the results were ambiguous. The final conclusion of the search for the Higgs particle at the LEP experiments is that we now know that the mass of the Higgs particle must be larger than 114 GeV.

Now the LEP experiments have finished taking data and a new, more powerful accelerator, the LHC, is getting ready for its first data run. With this accelerator many different kinds of experiments will take place. One of these is to continue the search for the Higgs particle. The scientists think that with the help of LHC will the existence of the Higgs particle finally be verified and its mass will be measured.