"Particle fireworks" from LEP's final fling
8 November 2000
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This dramatic "event display" is from the L3 experiment at the Large Electron Positron (LEP) collider, at the European centre for particle physics, CERN,
Geneva. LEP is scheduled to shut down forever this year, after 11
years, and this event is from high energy running (at a total energy of
205 GeV) during 2000.
In this event an electron and positron have annihilated at the heart of the L3 detector
to produce two W particles - carriers of the weak force - which decay
immediately. One W particle has decayed into two quarks, which create
two "jets" - the bursts of particles that shoot out towards the top right and the top left. The other W particle has decayed into a tau lepton
(a heavy relative of the electron) and its neutral partner, the
tau-neutrino. The tau decays before it leaves the beam pipe along the
centre of the detector, to produce a charged pion, which leaves the
single track pointing towards the bottom left, and an invisible
neutrino.
The outer purple blocks show energy deposited by hadrons
(particles, like pions, that contain quarks), while the long green
oblongs show the amount of energy deposited by photons and electrons.
The large cylinder indicates the extent of the "Time expansion chamber" which detects the tracks of electrically charged particles.
Credit: L3 experiment