Introduction to LEP physics
Introduction
DELPHI is one of the experiments at the LEP
Collider at CERN,
the European Laboratory for Particle Physics, near Geneva
(and, incidentally, birthplace of the World-Wide Web).
The LEP machine collides beams of matter (electrons) head on with
beams of antimatter (antielectrons, or positrons). When the matter and antimatter meet they
self-destruct in a burst of pure energy, which immediately rematerialises as newly created particles
of matter: energy has been converted into mass in accordance with Einstein's
famous equation E=mc2.
Design of DELPHI
The DELPHI experiment consists of layers of particle detectors which pick up the debris from
electron-positron collisions at the heart of the apparatus. Each layer performs a different task in
identifying the particles produced in a collision. This helps the physicists to work out what has
happened in a collision. Models like the ones you will see are computer reconstructions of
collisions, or "events" in DELPHI. They show where particles have left tracks and other clues in
the apparatus. By rotating the model, you can look at the event from different angles to work out
what is happening.
The Event Display
The cylinder shown in white in the model is the inner section of the detector. The collisions occur
in the very centre of the the model. Inside the cylinder, detectors reveal the tracks of charged
particles. The tracks are shown on the display as coloured lines. In the wall of the white cylinder
are other detectors, which slow most particles and measure the energy they give off. Outside the
cylinder are yet more detectors for other types of particle. From looking at which detectors pick up
readings, we can discover what has been produced in the event and other information such as the
speed and energy of these particles.
In this demonstration, you will be able to look at
a number of different events from DELPHI, each
showing a different type of particle interaction, with an explanation of what is happening. If you
like, once you have viewed all of the events you can take the Event
Quiz,where you will use your new-found knowledge to identify some more events.
More Information
For further information on DELPHI and LEP physics, or particle physics in general, these links may
be helpful.
Navigation links:
[Back to Introduction]
[How to use the Event Display]
http://hepwww.rl.ac.uk/WIRED/native-1.0/background.html
last modified on 10th July 1998 by Alastair Wilson (originally
based on descriptions in the Events in Delphi
pages, courtesy of Christine Sutton) for
Tim Adye, <T.J.Adye@rl.ac.uk>