Physics:Quantum quark: Difference between revisions

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


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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>
A '''quantum quark''' is an elementary fermion that carries color charge and participates in the strong interaction. Quarks combine through gluon-mediated quantum chromodynamics to form hadrons such as protons, neutrons, and mesons. They are not observed as isolated free particles under ordinary conditions.<ref name="gellmann1964">{{cite journal |last=Gell-Mann |first=M. |title=A Schematic Model of Baryons and Mesons |journal=Physics Letters |year=1964 |volume=8 |issue=3 |pages=214-215 |doi=10.1016/S0031-9163(64)92001-3}}</ref><ref name="pdg">{{cite journal |author=Particle Data Group |title=Review of Particle Physics |journal=Progress of Theoretical and Experimental Physics |year=2022 |volume=2022 |issue=8 |pages=083C01 |doi=10.1093/ptep/ptac097}}</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>
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== Flavors and color ==
The six quark flavors are up, down, charm, strange, top, and bottom. Each flavor appears in color states conventionally called red, green, and blue, together with corresponding antiquarks. Color is not ordinary visual color but a quantum charge of the strong interaction.<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>


== Overview ==
== Confinement ==
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" />
Quantum chromodynamics predicts that the force between separated color charges does not weaken in the same way as electromagnetism. Instead, quarks are confined inside color-neutral hadrons. High-energy collisions can produce jets that reflect the underlying quark and gluon dynamics.<ref name="gross1973">{{cite journal |last1=Gross |first1=David J. |last2=Wilczek |first2=Frank |title=Ultraviolet Behavior of Non-Abelian Gauge Theories |journal=Physical Review Letters |year=1973 |volume=30 |issue=26 |pages=1343-1346 |doi=10.1103/PhysRevLett.30.1343}}</ref><ref name="politzer1973">{{cite journal |last=Politzer |first=H. David |title=Reliable Perturbative Results for Strong Interactions? |journal=Physical Review Letters |year=1973 |volume=30 |issue=26 |pages=1346-1349 |doi=10.1103/PhysRevLett.30.1346}}</ref>
 
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 ==
== Hadron structure ==
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.
Baryons contain three valence quarks, while mesons contain a quark-antiquark pair, together with gluons and sea quark-antiquark pairs. The mass and spin of hadrons arise from a combination of quark masses, gluon fields, motion, and QCD binding energy.


== 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=
=See also=
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{{Author|Harold Foppele}}
{{Author|Harold Foppele}}


{{Sourceattribution|Quantum quark|1}}
{{Sourceattribution|Quark|1}}

Revision as of 20:39, 19 May 2026


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A quantum quark is an elementary fermion that carries color charge and participates in the strong interaction. Quarks combine through gluon-mediated quantum chromodynamics to form hadrons such as protons, neutrons, and mesons. They are not observed as isolated free particles under ordinary conditions.[1][2]

Complex yellow illustration of quark color charge, confinement, and hadron structure.

Flavors and color

The six quark flavors are up, down, charm, strange, top, and bottom. Each flavor appears in color states conventionally called red, green, and blue, together with corresponding antiquarks. Color is not ordinary visual color but a quantum charge of the strong interaction.[3]

Confinement

Quantum chromodynamics predicts that the force between separated color charges does not weaken in the same way as electromagnetism. Instead, quarks are confined inside color-neutral hadrons. High-energy collisions can produce jets that reflect the underlying quark and gluon dynamics.[4][5]

Hadron structure

Baryons contain three valence quarks, while mesons contain a quark-antiquark pair, together with gluons and sea quark-antiquark pairs. The mass and spin of hadrons arise from a combination of quark masses, gluon fields, motion, and QCD binding energy.


See also

Table of contents (84 articles)

Index

Full contents

References

  1. ↑ Gell-Mann, M. (1964). "A Schematic Model of Baryons and Mesons". Physics Letters 8 (3): 214-215. doi:10.1016/S0031-9163(64)92001-3. 
  2. ↑ Particle Data Group (2022). "Review of Particle Physics". Progress of Theoretical and Experimental Physics 2022 (8): 083C01. doi:10.1093/ptep/ptac097. 
  3. ↑ Griffiths, David J. (2008). Introduction to Elementary Particles (2nd ed.). Wiley-VCH. ISBN 978-3-527-40601-2. 
  4. ↑ Gross, David J.; Wilczek, Frank (1973). "Ultraviolet Behavior of Non-Abelian Gauge Theories". Physical Review Letters 30 (26): 1343-1346. doi:10.1103/PhysRevLett.30.1343. 
  5. ↑ Politzer, H. David (1973). "Reliable Perturbative Results for Strong Interactions?". Physical Review Letters 30 (26): 1346-1349. doi:10.1103/PhysRevLett.30.1346. 


Author: Harold Foppele


Source attribution: Quark

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