Jet (particle Physics)

Jet (particle Physics)

A jet is a narrow cone of hadrons and other particles produced by the hadronization of a quark or gluon in a particle physics or heavy ion experiment. Because of QCD confinement, particles carrying a color charge, such as quarks, cannot exist in free form. Therefore they fragment into hadrons before they can be directly detected, becoming jets. These jets must be measured in a particle detector and studied in order to determine the properties of the original quark.

In relativistic heavy ion physics, jets are important because the originating hard scattering is a natural probe for the QCD matter created in the collision, and indicate its phase. When the QCD matter undergoes a phase crossover into quark gluon plasma, the energy loss in the medium grows significantly, effectively quenching the outgoing jet.

Example of jet analysis techniques are:

• jet reconstruction (e.g., k_T algorithm, cone algorithm)
• jet correlation
• flavor tagging (e.g., b-tagging).

The Lund string model is an example of a jet fragmentation model.