The OPAL Experiment at CERN

The OPAL Experiment at the European Laboratory for Particle Physics (CERN)

The OPAL experiment at the CERN laboratory in Geneva, Switzerland studies in detail the electroweak force, one of the 4 fundamental forces in nature:

In the 1800's, James Clerk Maxwell and Michael Faraday caused a small revolution when they showed that electric and magnetic forces could be described in one unified electromagnetic theory. This work, you could say, set the stage for particle physics, where we are still searching for a GRAND UNIFIED theory which describes all 4 forces of nature in one unified theory. We don't have such a theory yet, but we've come a long way since the days of Maxwell and Faraday.

Over the past 30 years, many theoretical and experimental physicists have been studying the fundamental matter particles of nature and the interactions between them. From this work, we have formulated a 'Standard Model' of particle physics. In the Standard Model, the fundamental matter particles (quarks and leptons) interact via the exchange of particles. In the case of the electromagnetic force, charged particles interact via photon exchange. In the strong interaction, quarks interact via the exchange of gluons. And the weak interaction is mediated via exchange of the intermediate vector bosons, the W and Z particles. These W and Z particles were discovered in the 1980's at CERN. We speculate that the gravitational force is mediated via the exchange of gravitons, although we haven't seen any gravitons yet.

At the OPAL experiment at CERN, over 5 million Z bosons have been produced and their decays studied. We have used these Z particles to study in detail the nature of the electroweak force. The Z bosons are produced by colliding a beam of electrons into a beam of positrons, at just the right energy to make Z bosons.

The LEP (Large Electron Positron) Collider at the CERN laboratory is approximately 27 km in circumference, and is shown below, passing under the Swiss and French countryside near Geneva, Switzerland.

Take a short tour of the OPAL detector

See what some real particle physics events from the point of view of the OPAL detector.

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janis@physics.ubc.ca