In a proton-proton collision a large number of particles are produced. Most particles interact with different parts of the detector and are visible as traces in the detector called "tracks". The ATLAS detector consists of several components, stacked so that all particles go through the different layers sequentially. The various layers allow us to identify the type of particle and measure its direction, charge, momentum, energy, etc.

The electrons (which are constituents of the atom) stop at electromagnetic calorimeters (green in the display) and the muons (200 times heavier than the electrons, constituents of the cosmic rays) pass through all detectors and stop at the outer layer, which are the muon chambers (blue in the display). Below the event displays there is a table with all the tracks, which shows their total momentum, the momentum in the transverse plane (pT) and their angles. One can pick the tracks, or apply cuts. You can also select a particular event from a list of events.