A particle's path can thus be measured to a small fraction of a millimeter. Leaving the central tracking devices, the particles enter the detectors' calorimeters, which measure their energy. As the particles traverse the calorimeters, they lose their energy to a succession of dense, absorbent materials. Passing through layers of heavy metal plates, they create showers of light. Detectors record the intensity of the light flashes, a measure of the energy of the particle that passed through.
Most particles sputter out on their trip through the calorimeters.
However, one persistent particle, the muon, usually muscles its way through the tracking devices and calorimeters. Special muon detection chambers are located outside the calorimeters and record the flight of these long-lived particles. Various types of detection devices It is impossible to record each of the million or more collisions that occur in the CDF and DZero detectors every second. Preprogrammed triggers weed out ho-hum events, registering details of only the most interesting of these collisions for later analysis. Of the billions of recorded signatures, a handful hold evidence for new phenomena.