DELPHI is one of the experiments at the LEP
Collider at CERN, the European Laboratory for
Particle Physics, near Geneva. 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 into mass in accordance with Einsten's famous equation
E=mc2

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 - just as detectives put together
evidence at the scene of a crime. If you would like to find out
more about particle physics before you follow this trail, look here.
If you would like to try a more difficult identification
exercise, look here.
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