Hadrons are further classified by their spin and quark content.
Baryons are composed of three quarks or three anti-quarks and have half-odd-integral spin, i.e. they are fermions. They include the nucleons (the proton and the neutron), which are part of normal atomic nuclei, and particles such as the hyperons (e.g. the Δ, Λ, Σ, Ξ, and Ω), which are generally heavier than nucleons, short-lived, and do not normally appear in atomic nuclei.
Mesons are composed of a quark and an anti-quark and have integral spin, i.e. they are bosons. They include the pions, the kaons, the rhos, the omegas, and many other types of mesons.
Exotic hadrons do not have the quark numbers of either ordinary baryons or mesons.
Exotic baryons are composed of more than three quarks (or anti-quarks) odd in number. The first such particles, pentaquarks, are thought to have been discovered recently. They have four quarks and one anti-quark.
Exotic mesons contain more than one valence quark-antiquark pair. Recently there has been some evidence for the tetraquark, which consists of two valence quark-antiquark pairs.
Hybrid mesons consist of at least one valence quark-antiquark pair and at least one real (not virtual) gluon.
Glueballs contain no valence quarks at all, being composed solely of gluons. These states mix strongly with ordinary mesons and are extremely difficult to identify.
As the hadrons are composite quantum systems, they also exist in excited states known as hadronic resonances. Each ground state hadron may have many excited states, and hundreds have been observed in particle experiments. Resonances decay extremely quickly (within about 10−24 s) via strong interactions.
This site introduces the most exciting scientific adventure of the next decade and is for anyone interested in how we might answer some of the fundamental questions we have about the Universe we live in.
The LHC (Large Hadron Collider) is an international project, in which the UK has a leading role.
This site includes the latest news from the project, accessible explanations of how the LHC works, how it is funded, who works there and what benefits it brings us.
The processes of hadron formation are taken to be sensitive only to the probabilities, and not the amplitudes, for the possible configurations of the parton system.
If the formation of hadrons does not occur in some such local and universal manner, there seems little hope of obtaining useful predictions from QCD without very detailed knowledge of the structure of hadrons.
In addition to single hadron inclusive spectra, fragmentation functions may also be used to describe multihadron spectra [12,13].
Share your thoughts, questions and commentary here
Want to know more? Search encyclopedia, statistics and forums:
Press Releases |
The Wikipedia article included on this page is licensed under the
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m