Editing Hadron (section)

==Properties==
[[Image:Hadron colors.svg|right|thumb|upright|All types of hadrons have zero total color charge (three examples shown).|alt=A green and a magenta ("antigreen") arrow canceling out each other out white, representing a meson; a red, a green, and a blue arrow canceling out to white, representing a baryon; a yellow ("antiblue"), a magenta, and a cyan ("antired") arrow canceling out to white, representing an antibaryon.]]

According to the [[quark model]],<ref name=Amsler-etal-2008-PDG/> the properties of hadrons are primarily determined by their so-called ''[[valence quark]]s''. For example, a [[proton]] is composed of two [[up quark]]s (each with [[electric charge]] {{frac|+|2|3}}, for a total of +{{frac|4|3}} together) and one [[down quark]] (with electric charge {{frac|−|1|3}}). Adding these together yields the proton charge of +1. Although quarks also carry [[color charge]], hadrons must have zero total color charge because of a phenomenon called [[color confinement]]. That is, hadrons must be "colorless" or "white". The simplest ways for this to occur are with a quark of one color and an [[antiparticle|antiquark]] of the corresponding anticolor, or three quarks of different colors. Hadrons with the first arrangement are a type of [[meson]], and those with the second arrangement are a type of [[baryon]].

Massless virtual gluons compose the overwhelming majority of particles inside hadrons, as well as the major constituents of its mass (with the exception of the heavy [[charm quark|charm]] and [[bottom quark]]s; the [[top quark]] vanishes before it has time to bind into a hadron). The strength of the [[Strong interaction|strong-force]] [[gluon]]s which bind the quarks together has sufficient energy ({{mvar|E}}) to have resonances composed of massive ({{mvar|m}}) quarks ([[Mass–energy equivalence|{{mvar|E}} ≥ {{mvar|mc}}<sup>2</sup>]]). One outcome is that short-lived pairs of [[virtual particle|virtual]] quarks and antiquarks are continually forming and vanishing again inside a hadron. Because the virtual quarks are not stable wave packets (quanta), but an irregular and transient phenomenon, it is not meaningful to ask which quark is real and which virtual; only the small excess is apparent from the outside in the form of a hadron. Therefore, when a hadron or anti-hadron is stated to consist of (typically) two or three quarks, this technically refers to the constant excess of quarks versus antiquarks.

Like all [[subatomic particle]]s, hadrons are assigned [[quantum number]]s corresponding to the [[Representation theory|representations]] of the [[Poincaré group]]: {{math|''J''{{sup|PC}} }}({{mvar|m}}), where {{mvar|J}} is the [[Spin (physics)|spin]] quantum number, {{math|P}} the intrinsic parity (or [[Parity (physics)|P-parity]]), {{math|C}} the charge conjugation (or [[C-parity]]), and {{mvar|m}} is the particle's [[mass]]. Note that the mass of a hadron has very little to do with the mass of its valence quarks; rather, due to [[mass–energy equivalence]], most of the mass comes from the large amount of energy associated with the [[strong interaction]]. Hadrons may also carry [[flavour quantum number|flavor quantum numbers]] such as [[isospin]] ([[G-parity]]), and [[strangeness]]. All quarks carry an additive, conserved quantum number called a [[baryon number]] ({{mvar|B}}), which is {{frac|+|1|3}} for quarks and {{frac|−|1|3}} for antiquarks. This means that baryons (composite particles made of three, five or a larger odd number of quarks) have  {{mvar|B}}&nbsp;=&nbsp;1  whereas mesons have {{mvar|B}}&nbsp;=&nbsp;0.

Hadrons have [[excited state]]s known as [[resonance (particle physics)|resonances]]. Each [[ground state]] hadron may have several excited states; several hundred different resonances have been observed in experiments. Resonances decay extremely quickly (within about 10{{sup|−24}}&nbsp;[[second]]s) via the strong nuclear force.

In other [[phase (matter)|phases]] of [[matter]] the hadrons may disappear.  For example, at very high temperature and high pressure, unless there are sufficiently many flavors of quarks, the theory of [[quantum chromodynamics]] (QCD) predicts that quarks and [[gluon]]s will no longer be confined within hadrons, "because the [[coupling constant|strength]] of the strong interaction [[coupling constant#Running coupling|diminishes with energy]]". This property, which is known as [[asymptotic freedom]], has been experimentally confirmed in the energy range between 1&nbsp;[[GeV]] (gigaelectronvolt) and 1&nbsp;[[TeV]] (teraelectronvolt).<ref name=Bethke-2007/> All [[free particle|free]] hadrons [[proton decay|except (''possibly'') the proton and antiproton]] are [[Exponential decay|unstable]].