The purpose of these web pages 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. This experiment that runs at LEP (the Large Electron-Positron collider), which is the largest particle accelerator in the world.

The emphasis is very much on your active participation. I 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.

Table of Contents   Introduction The Detector and How to Understand the Event Pictures The Challenge (Part 1) How to Identify Events Containing a Particle-Antiparticle Pair The Challenge (Part 2) How to Identify Events Containing a Pair of W Particles The Challenge (Part 3) The Challenge (Part 4) How to Identify Slightly More Complicated Types of Event The Challenge (Part 5) A Different Sort of Challenge: Making Measurements Measuring Z0 decays Measuring W decays

If you enjoyed looking at these events then you might be interested in finding out more about particle physics on the web.

Notes for those looking at this website as part of the The National Particle Physics Masterclass.

1) You are probably looking at a local copy of the website. The definitive version of the site is available at the address: http://hepwww.ph.man.ac.uk/~wyatt/events/home.html, which will be maintained and extended in the coming months/years.
2) There are more challenges than you could possibly complete in the one to two hours you will be spending on these pages during the masterclass. However, I hope some of you will be interested in continuing to work at the challenges at home/school after the masterclass. (If so, please use the definitive address for the website given above.)

Acknowledgements.