Editing Quark (section)

=== Strong interaction and color charge ===
{{See also|Color charge|Strong interaction}}
[[Image:Hadron colors.svg|right|thumb|upright|All types of hadrons have zero total color charge.|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.]]
[[File:Strong force charges.svg|200px|left|thumb|The pattern of strong charges for the three colors of quark, three antiquarks, and eight gluons (with two of zero charge overlapping).]]
According to [[quantum chromodynamics]] (QCD), quarks possess a property called ''[[color charge]]''. There are three types of color charge, arbitrarily labeled ''blue'', ''green'', and ''red''.<ref group="nb">Despite its name, color charge is not related to the color spectrum of visible light.</ref> Each of them is complemented by an anticolor – ''antiblue'', ''antigreen'', and ''antired''. Every quark carries a color, while every antiquark carries an anticolor.<ref>
{{cite web
 |author=R. Nave
 |title=The Color Force
 |url=http://hyperphysics.phy-astr.gsu.edu/hbase/forces/color.html#c2
 |work=[[HyperPhysics]]
 |publisher=[[Georgia State University]], Department of Physics and Astronomy
 |access-date=2009-04-26
}}</ref>

The system of attraction and repulsion between quarks charged with different combinations of the three colors is called [[strong interaction]], which is mediated by [[force carrier|force carrying particles]] known as ''[[gluon]]s''; this is discussed at length below. The theory that describes strong interactions is called [[quantum chromodynamics]] (QCD). A quark, which will have a single color value, can form a [[bound state|bound system]] with an antiquark carrying the corresponding anticolor. The result of two attracting quarks will be color neutrality: a quark with color charge ''ξ'' plus an antiquark with color charge −''ξ'' will result in a color charge of 0 (or "white" color) and the formation of a [[meson]]. This is analogous to the [[additive color]] model in basic [[optics]]. Similarly, the combination of three quarks, each with different color charges, or three antiquarks, each with different anticolor charges, will result in the same "white" color charge and the formation of a [[baryon]] or [[antibaryon]].<ref>
{{cite book
 |author=B. A. Schumm
 |title=Deep Down Things
 |pages=[https://archive.org/details/deepdownthingsbr00schu/page/131 131–132]
 |publisher=[[Johns Hopkins University Press]]
 |year=2004
 |isbn=978-0-8018-7971-5
 |url=https://archive.org/details/deepdownthingsbr00schu/page/131
}}</ref>

In modern particle physics, [[gauge symmetry|gauge symmetries]] – a kind of [[symmetry group]] – relate interactions between particles (see [[gauge theories]]). Color [[SU(3)]] (commonly abbreviated to SU(3)<sub>c</sub>) is the gauge symmetry that relates the color charge in quarks and is the defining symmetry for quantum chromodynamics.<ref name="PeskinSchroeder">Part III of
{{cite book
 |author1=M. E. Peskin
 |author2=D. V. Schroeder
 |title=An Introduction to Quantum Field Theory
 |url=https://archive.org/details/introductiontoqu0000pesk
 |url-access=registration
 |publisher=[[Addison–Wesley]]
 |year=1995
 |isbn=978-0-201-50397-5
}}</ref> Just as the laws of physics are independent of which directions in space are designated ''x'', ''y'', and ''z'', and remain unchanged if the coordinate axes are rotated to a new orientation, the physics of quantum chromodynamics is independent of which directions in three-dimensional color space are identified as blue, red, and green. SU(3)<sub>c</sub> color transformations correspond to "rotations" in color space (which, mathematically speaking, is a [[complex vector space|complex space]]). Every quark flavor ''f'', each with subtypes ''f''<sub>B</sub>, ''f''<sub>G</sub>, ''f''<sub>R</sub> corresponding to the quark colors,<ref>
{{cite book
 |author=V. Icke
 |title=The Force of Symmetry
 |url=https://archive.org/details/forceofsymmetry0000icke
 |url-access=registration
 |page=[https://archive.org/details/forceofsymmetry0000icke/page/216 216]
 |publisher=[[Cambridge University Press]]
 |year=1995
 |isbn=978-0-521-45591-6
}}</ref> forms a triplet: a three-component [[quantum field]] that transforms under the fundamental [[representation theory|representation]] of SU(3)<sub>c</sub>.<ref>
{{cite book
 |author=M. Y. Han
 |title=A Story of Light
 |url=https://archive.org/details/storylightshorti00hanm_264
 |url-access=limited
 |page=[https://archive.org/details/storylightshorti00hanm_264/page/n86 78]
 |publisher=[[World Scientific]]
 |year=2004
 |isbn=978-981-256-034-6
}}</ref> The requirement that SU(3)<sub>c</sub> should be [[local symmetry|local]] – that is, that its transformations be allowed to vary with space and time – determines the properties of the strong interaction. In particular, it implies the existence of [[Gluon#Eight colors|eight gluon types]] to act as its force carriers.<ref name="PeskinSchroeder"/><ref>
{{cite encyclopedia
 |author=C. Sutton
 |title=Quantum Chromodynamics (physics)
 |url=http://www.britannica.com/EBchecked/topic/486191/quantum-chromodynamics#ref=ref892183
 |encyclopedia=[[Encyclopædia Britannica Online]]
 |access-date=2009-05-12
}}</ref>