imported>WikiHarold: Replace raw Quantum Collection backlink with BM backlink template

2026-05-08T18:43:33Z

Replace raw Quantum Collection backlink with BM backlink template

← Older revision	Revision as of 18:43, 8 May 2026
(No difference)

imported>WikiHarold: Replace raw Quantum Collection backlink with BM backlink template

2026-05-08T18:43:33Z

Replace raw Quantum Collection backlink with BM backlink template

New page

{{Short description|Elementary fermion that carries color charge}}

{{Quantum matter backlink|Particles}}
[[Book:Quantum Collection/Matter (by scale)|<- Back to Matter by scale]]

A '''quark''' is an [[Physics:Quantum elementary particle|elementary particle]] and a type of [[Physics:Quantum fermion|fermion]]. Quarks carry color charge and interact through the strong interaction described by [[Physics:Quantum chromodynamics|quantum chromodynamics]] (QCD). They are constituents of composite particles such as protons, neutrons and mesons.<ref name="griffiths">{{cite book |last=Griffiths |first=David J. |title=Introduction to Elementary Particles |edition=2nd |publisher=Wiley-VCH |year=2008 |isbn=978-3-527-40601-2}}</ref><ref name="halzen">{{cite book |last1=Halzen |first1=Francis |last2=Martin |first2=Alan D. |title=Quarks and Leptons: An Introductory Course in Modern Particle Physics |publisher=Wiley |year=1984 |isbn=978-0-471-88741-6}}</ref>

Quarks are not observed as isolated free particles under ordinary conditions. In QCD, the interaction energy between separated color charges leads to confinement, so quarks appear inside hadrons or in high-energy states such as quark-gluon plasma.<ref name="peskin">{{cite book |last1=Peskin |first1=Michael E. |last2=Schroeder |first2=Daniel V. |title=An Introduction to Quantum Field Theory |publisher=Addison-Wesley |year=1995 |isbn=978-0-201-50397-5}}</ref>
[[File:Quark flavours.png|450px|thumb|Quark flavors, color charge, and the structure of hadrons in quantum chromodynamics (QCD).]]

=Overview=

Quarks have spin <math>\tfrac{1}{2}</math>, so they obey Fermi-Dirac statistics. Each quark also has an antiquark with opposite electric charge and opposite color charge. Quarks participate in the strong, weak and electromagnetic interactions, while neutrally charged leptons do not participate in the strong interaction.<ref name="griffiths" />

The known quark flavors are up, down, charm, strange, top and bottom. Up-type quarks have electric charge <math>+2/3</math> in units of the elementary charge. Down-type quarks have electric charge <math>-1/3</math>. Ordinary atomic nuclei are built from protons and neutrons, whose valence structure is dominated by up and down quarks.<ref name="halzen" />

=Color charge and confinement=

In QCD, quarks carry color charge rather than ordinary visual color. The three color labels are conventionally called red, green and blue. Gluons mediate the strong interaction and also carry color charge, which makes QCD a non-Abelian gauge theory.<ref name="peskin" />

Color confinement means that isolated quarks are not detected as separate particles at low energy. When a high-energy collision produces quarks, the observed final state is a set of hadrons formed by hadronization. This behavior is central to the experimental study of quarks in particle accelerators.

=Hadrons=

Quarks combine into color-neutral composite particles. Baryons contain three valence quarks; the proton has valence content <math>uud</math>, and the neutron has valence content <math>udd</math>. Mesons contain a quark and an antiquark. The full quantum state of a hadron also includes gluons and sea quark-antiquark pairs.

=History=

Murray Gell-Mann and George Zweig proposed quark-like constituents in 1964 as a way to organize the observed hadron spectrum.<ref name="gellmann1964">{{cite journal |last=Gell-Mann |first=M. |title=A Schematic Model of Baryons and Mesons |journal=Physics Letters |volume=8 |issue=3 |pages=214-215 |year=1964 |doi=10.1016/S0031-9163(64)92001-3 |bibcode=1964PhL.....8..214G}}</ref><ref name="zweig1964">{{Cite report |last=Zweig |first=G. |title=An SU(3) Model for Strong Interaction Symmetry and its Breaking |publisher=CERN |year=1964 |number=CERN-TH-401}}</ref> Deep inelastic scattering experiments later showed that nucleons contain point-like charged constituents, which supported the quark picture.<ref name="friedman1991">{{cite journal |last=Friedman |first=Jerome I. |title=Deep inelastic scattering: Comparisons with the quark model |journal=Reviews of Modern Physics |volume=63 |issue=3 |pages=615-629 |year=1991 |doi=10.1103/RevModPhys.63.615 |bibcode=1991RvMP...63..615F}}</ref>

=See also=
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also/Matter}}

=References=
{{reflist|3}}

{{Author|Harold Foppele}}

{{Sourceattribution|Quantum quark|1}}

Physics:Quantum quark - Revision history

imported>WikiHarold: Replace raw Quantum Collection backlink with BM backlink template

imported>WikiHarold: Replace raw Quantum Collection backlink with BM backlink template