Narrow Results

The paper deals with an approach to the model-independent searching for the Z' gauge boson as a virtual state in scattering processes. The relations between the Z' couplings to fermions covering a wide class of models beyond the Standard Model are found and used. They reduce in an essential way the number of parameters to be fitted in experiments. Special observables which uniquely pick out the Z' at energies of LEP and ILC colliders in different leptonic processes are introduced and the data of LEP experiments are analyzed. The Z' couplings to leptons and quarks are estimated at 95% confidence level. At this level, the LEP data are compatible with the existence of the Z' with the mass m_Z′ ~ 1–1.2 TeV. These estimates may serve as a guide for experiments at the Tevatron and/or LHC. A comparison with other approaches and results is given.

Since no Standard Model Higgs was discovered at LEP the searches were extended to beyond the Standard Model Higgs scenarios. A selection of final results from searches carried out by the four LEP experiments ALEPH, DELPHI, L3 and OPAL are presented that include data taken at the highest centre-of-mass energies.