Probing the Standard Model with electron-positron annihilations at LEP

(DELPHI experiment, CERN Geneva, Switzerland 1987-1990).

In addition to a heavy involvement in the preparation studies (detector simulations)

to determine the sensitivity for certain physics processes and the coordination of the

offline analysis processing, my main analysis effort was focused on the following two subjects :

This project, of which I was workgroup coordinator, was aimed at the development

of physics criteria to detect the decay of a light minimal standard model Higgs particle.

The main focus was here at 4-lepton events and events consisting of 2 leptons and 2 jets.

In case no positive signal was observed, an increasing lowerlimit for the Higgs mass was

determined, within the framework of the standard model, based on the steadily increasing

number of observed Z events.

In this investigation an energy scan around the Z peak was performed to determine

the cross sections of the Z decays in the various decay channels.

Comparison of these cross sections and the widths enabled a quantitative test of the

validity of the standard model.