A collimated collection of final hadrons associated with an energetic parton and its radiation and hadronization. A precise perturbative prediction requires an infrared-safe observable that specifies how particles are grouped into jets.
In inclusive electron-positron annihilation into hadrons, hard gluon radiation produces a quark, an antiquark and a gluon, giving three resolved particle jets. Observation of such events at PETRA in 1979 provided direct evidence for gluons. The institutional account is www.desy.de/news/news_search/index_eng.html?openDirectAnchor=1643&printversion=1 .
Articles by others on the same topic
In particle physics, a "jet" refers to a collimated spray of particles that is produced when a high-energy quark or gluon hadronizes, or transforms into a collection of particles, after being produced in high-energy collisions such as those occurring in particle accelerators (for example, at the Large Hadron Collider).