Particle identification

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Particle identification is the process of using information left by an particle passing through a particle detector to identify the type of particle.

[edit] At modern collider detectors

Particle identification is increasingly complex in modern particle physics, as new machines such as the Large Hadron Collider produce extremely energetic particles that are difficult to distinguish, and requires detailed study and a variety of techniques. Some methods used in hermetic detectors at colliders include:

• Quark flavor tagging, i.e. identifying what flavor of quark a jet comes from. B-tagging, the identification of bottom quarks, is the most important example. Charm tagging is also possible, but extremely difficult. Tagging jets from lighter quarks is simply impossible!
• Tau identification requires differentiating the narrow "jet" produced by the hadronic decay of the tau from ordinary quark jets.
• Muon identification requires an entire specialized detector system outside the calorimeter, since high energy muons typically pass through all other detector layers nearly intact.
• Photons are identified because they leave all their energy in a detector's electromagnetic calorimeter, but do not appear in the Inner Detector (see, for example, ATLAS Inner Detector) because they are neutral. A neutral pion which decays inside the EM calorimeter can fake this effect.
• Electrons appear as a track in the inner detector and deposit all their energy in the electromagnetic calorimeter.