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Quark

From Tilcayo Cats, the lean encyclopaedia by Tilcayo Knowledge Systems

A quark is an elementary particle and one of the two basic types of particle that make up matter; the other type is the lepton.[1] Quarks are the building blocks of particles such as the proton and the neutron. A proton is made of two up quarks and one down quark, and a neutron of one up quark and two down quarks.[2]

History

Quarks were first proposed separately by the American physicists Murray Gell-Mann and George Zweig in 1963.[3] The first quark model used three quarks, called up, down and strange.[4] Later discoveries needed more types. In 1995, two groups at Fermilab confirmed that the top quark exists, completing the set of six.[5]

The six quarks

There are six types, or "flavours", of quark, arranged in three generations: the up and down quarks; the charm and strange quarks; and the top and bottom (or beauty) quarks.[6] All stable matter in the universe is made from particles of the first generation, because heavier particles quickly decay.[7]

Properties

Unlike any particle that has been seen on its own, quarks have charges that are fractions of the electron's charge: +2/3 or −1/3 (and the opposite for antiquarks).[8] Quarks are never found alone. This idea, called quark confinement, explains how quarks can exist but never be isolated or directly observed.[9] Particles made of three quarks, such as protons and neutrons, are called baryons, and particles made of a quark and an antiquark are called mesons.[10]

Quarks feel the strong force, which is carried by the gluon.[11] The theory of quarks and the strong force is called quantum chromodynamics.[12]

See also

References

  1. ↑ "The Standard Model". CERN. Retrieved 20 October 2026. These particles occur in two basic types called quarks and leptons.
  2. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. Similar comments apply to the neutron n , which is composed of the three quarks udd .
  3. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. Quarks were first proposed independently by American physicists Murray Gell-Mann and George Zweig in 1963.
  4. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. These quark flavors are named up ( u ), down ( d ), and strange ( s ).
  5. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. In 1995, two groups at Fermilab confirmed the top quark's existence
  6. ↑ "The Standard Model". CERN. Retrieved 20 October 2026. The six quarks are paired in the three generations
  7. ↑ "The Standard Model". CERN. Retrieved 20 October 2026. All stable matter in the universe is made from particles that belong to the first generation; any heavier particles quickly decay to the next most stable level.
  8. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. The most radical proposal by Gell-Mann and Zweig is the fractional charges of quarks
  9. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. This is part of the theory of quark confinement , which explains how quarks can exist and yet never be isolated or directly observed.
  10. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. Mesons are combinations of a quark and an antiquark.
  11. ↑ "The Standard Model". CERN. Retrieved 20 October 2026. the strong force is carried by the "gluon"
  12. ↑ "33.5 Quarks: Is That All There Is?". College Physics 2e. OpenStax. Retrieved 20 October 2026. Quark theory including color is called quantum chromodynamics (QCD), also named by Gell-Mann.
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