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Introduction to the DELPHI experiment

Particle Physics Basics and Experimental Goals
Particle physics studies the most basic building blocks of the matter, investigating subatomic processes in attempt to describe the essence of the Universe. Recently, a rapid progress in our understanding of its laws occured. Discovery of intermediate vector bosons, W^+- and Z⁰, in 1983 at the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland, provided a strong support to the electroweak theory, developed during 1960s. In 1970s, the Quantum Chromodynamics (QCD) was developed as the theory of strong interaction between quarks, introducing gluons as quanta of the strong field. The combination of the electroweak theory and QCD, called the Standard Model, proved to be a highly successful framework. The Standard Model operates with two families of fermions: leptons and quarks, that build up matter and interact by means of bosons: gamma, W^+-, Z⁰ and gluon. Elementary particles are subdivided into three generations.

An ideal laboratory to study electroweak and strong interactions is the electron-positron annihilation at high energy, where collision of electron and positron gives way to production of gauge bosons Z⁰ and W^+-.

In 1989, the largest contemporary accelerator, the LEP collider, began operation in CERN. Four detectors devoted to the electron-positron annihilation experiments, including DELPHI, were installed at the collider ring. Primary experimental goals are to provide thorough Standard Model studies, precise QCD analysis, and possibly to investigate the problem of Higgs - a hypothetical particle, associated with the electroweak symmetry breaking mechanism, and that requires the W and Z bosons to have mass.