The purpose of this masterclass is to allow you to identify for yourself some interesting particle physics interactions or "events". These events have been seen using an experiment called OPAL, at CERN, near to Geneva, Switzerland. This experiment ran at LEP (the Large Electron-Positron collider).
The emphasis is very much on your active participation. We have tried to explain as simply as possible a few important things you need to know about our experiment and the different types of events that can occur. But the main parts are where you play the role of "particle detective" and identify for yourself pictures of different types of event.