The first and the last OPAL event Between 1989 and 2000 the OPAL experiment at the LEP accelerator has collected data from millions of electron-positron interactions. Every single interaction recorded by the detector is called an 'event'. The data recorded for an event can be visualised by an event display. The event displays which you find on this page always show the plane perpendicular to the beam. You see the small beam pipe in the centre. Surrounding it are the tracking chambers which detect charged particles. The curvature of the tracks is a measure of their momentum. Charged and neutral particles (apart from neutrinos which cannot be detected) deposit energy in the calorimeters outside the tracking chambers. The size of the blobs shown is proportional to the amount of energy deposited. OPAL data taking ended finally on 2 November 2000 in the morning. On this page we show you the first event and the last 100 events observed in the OPAL detector

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The electron and positron beam annihilate to from a Z boson which decays into two quarks. The two quarks form hadronic jets which are observed in the calorimeter. At the moment where the event was observed the tracking chambers were not yet fully operational and no particle tracks are seen in the central detector.

The last event Cycling display (automatic) Step through at your own speed

One hundred of the last events collected by OPAL. A selection is applied to the sample so that many of the hundred should be interesting physics events: but some of them will not be! Looking at these events is therefore a matter of luck: but you might see some new or very rare physics process as it happens!

Cycling display (automatic) Step through at your own speed

These events were collected in the last few days of 1998 data taking. A short description is given for each of the events: by browsing these you may come to recognise some of the different types of events. The event on the right shows the production of two W bosons. Each of them decays into two jets which are visible in the detector.