A hadron, in particle physics, is a subatomic particle which experiences the nuclear force. These are not fundamental particles but are composed of fermions, called quarks and antiquarks, and of bosons, called gluons. The gluons mediate the color force that binds the quarks together. Thousands of particles explode from the collision point of two relativistic (100 GeV per ion) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... A subatomic particle is a particle smaller than an atom: it may be elementary or composite. ... A Feynman diagram of a strong proton-neutron interaction mediated by a neutral pion. ... In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ... These are the six flavors of quarks and their most likely decay modes. ... In particle physics, bosons, named after Satyendra Nath Bose, are particles having integer spin. ... In particle physics, gluons are subatomic particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei. ... Quantum chromodynamics (QCD) is the theory of the strong interaction, a fundamental force describing the interactions of the quarks and gluons found in nucleons (such as the proton and neutron). ...

Like all subatomic particles, hadrons have quantum numbers corresponding to the representations of the Poincaré group: J^PC(m), where J is the spin, P, the parity, C, the C parity, and m, the mass. In addition they may carry flavour quantum numbers such as isospin (or G parity), strangeness etc. Hadrons can be further divided into two classes: A subatomic particle is a particle smaller than an atom: it may be elementary or composite. ... A quantum number is a number used to parametrise certain properties of particles or other systems in quantum mechanics. ... In mathematics Representation theory is the name given to the study of standard representations of abstract mathematical structures. ... In physics and mathematics, the Poincaré group is the group of isometries of Minkowski spacetime. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... Look up Parity in Wiktionary, the free dictionary Parity is a concept of equality of status or functional equivalence. ... C parity or charge parity is a multiplicative quantum number of some particles that describes its behavior under a symmetry operation of charge conjugation (see C-symmetry). ... Flavour (or flavor) is a quantum number of elementary particles related to their weak interactions. ... Isospin (isotopic spin, isobaric spin) is a physical quantity which is mathematically analogous to spin. ... In theoretical physics, G-parity is a multiplicative quantum number that results from the generalization of C-parity to multiplets of particles. ... In particle physics, strangeness, denoted as , is a property of particles, expressed as a quantum number for describing decay of particles in strong and electro-magnetic reactions, which occur in a short period of time. ...

• Baryons are fermions. They always carry an additive conserved quantum number called baryon number (B). B=1 for nucleons (the proton and the neutron), which are part of the atomic nucleus.
• Mesons are bosons with B=0.

Most hadrons can be classified by the quark model which posits that all the quantum numbers of baryons are derived from those of the valence quarks. For a baryon these are three quarks and for a meson these are a quark-antiquark pair. Each quark is thus a fermion with B=1/3. Excited baryon or meson states are known as 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. Combinations of three u, d or s-quarks with a total spin of 3/2 form the so-called baryon decuplet. ... In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ... In particle physics, the baryon number is an approximate conserved quantum number. ... In physics a nucleon is a collective name for two baryons: the neutron and the proton. ... In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... This article or section does not adequately cite its references or sources. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... Mesons of spin 1 form a nonet In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... In particle physics, bosons, named after Satyendra Nath Bose, are particles having integer spin. ... In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks, ie, the quarks (and antiquarks) which give rise to the quantum numbers of the hadrons. ... These are the six flavors of quarks and their most likely decay modes. ... In physics, resonance is the tendency of a system to absorb more oscillatory energy when the frequency of the oscillations matches the systems natural frequency of vibration (its resonant frequency) than it does at other frequencies. ...

Mesons which lie outside the quark model classification are called exotic mesons. These include glueballs, hybrid mesons and tetraquarks. The only baryons which lie outside the quark model at present are the pentaquarks, but evidence for their existence is unclear as of 2006. Identities and classification of possible tetraquark mesons. ... A pentaquark is a subatomic particle consisting of a group of five quarks (compared to three quarks in normal baryons and two in mesons), or more specifically four quarks and one anti-quark. ... For the Manfred Mann album, see 2006 (album). ...

All hadrons are single particle excitations of the basic theory of strong interactions, called quantum chromodynamics. Due to a property called confinement that this theory enjoys at energies below the QCD scale, these excitations are not quarks and gluons, which are the basic fields, but the hadrons which are composite, and carry no color charge. The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... Quantum chromodynamics (QCD) is the theory of the strong interaction, a fundamental force describing the interactions of the quarks and gluons found in nucleons (such as the proton and neutron). ... Colour confinement (often just confinement) is the physics phenomenon that color charged particles (such as quarks) cannot be isolated. ... In particle physics, QCD scale is the energy scale (or length scale) associated with the processes of Quantum chromodynamics (QCD), i. ... These are the six flavors of quarks and their most likely decay modes. ... In particle physics, gluons are subatomic particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei. ... In quantum chromodynamics (QCD), color or color charge refers to a certain property of the subatomic particles called quarks. ...

In other phases of QCD matter the hadrons may disappear. For example, at very low temperature and low pressure, unless there are sufficiently many very massive flavors of quarks, QCD predicts that quarks and gluons will interact weakly and in particular no longer be confined. This property, which is known as asymptotic freedom, has been experimentally confirmed at the energy scales between a GeV and a TeV. Quark matter or QCD matter refers to any of a number of phases of matter whose degrees of freedom include quarks and gluons. ... In physics, asymptotic freedom is the property of some gauge theories in which the interaction between the particles, such as quarks, becomes arbitrarily weak at ever shorter distances, i. ...

See also

• Subatomic particles: list of particles, leptons
• Quantum chromodynamics, quark model, confinement
• Quark Star
• QCD matter

A subatomic particle is a particle smaller than an atom: it may be elementary or composite. ... This is a list of particles in particle physics, including currently known and hypothetical elementary particles, as well as the composite particles that can be built up from them. ... In physics, a particle is a lepton if it has a spin of 1/2 and does not experience the strong nuclear force. ... Quantum chromodynamics (QCD) is the theory of the strong interaction, a fundamental force describing the interactions of the quarks and gluons found in nucleons (such as the proton and neutron). ... In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks, ie, the quarks (and antiquarks) which give rise to the quantum numbers of the hadrons. ... Colour confinement (often just confinement) is the physics phenomenon that color charged particles (such as quarks) cannot be isolated. ... A strange star or quark star is a hypothetical type of star composed of strange matter, or quark matter. ... Quark matter or QCD matter refers to any of a number of phases of matter whose degrees of freedom include quarks and gluons. ...

References and external links

• The Particle Data Group[1] maintains listings of properties of all known particles.

The Particle Data Group is an international collaboration of particle physicists that compiles and reanalyzes published results related to the properties of particles and fundamental interactions. ...