quark


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quark

(kwôrk): see elementary particleselementary particles,
the most basic physical constituents of the universe. Basic Constituents of Matter

Molecules are built up from the atom, which is the basic unit of any chemical element. The atom in turn is made from the proton, neutron, and electron.
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.

quark

(kwork, kwark) Any of six pointlike elementary particles (the up, down, strange, charm, bottom, and top quarks) that are thought to be the structural units from which other particles (excluding leptons) are formed. In the usual scheme, quarks all have spin ½, electric charges that are –⅓ or ⅔ of the proton charge, and other innate qualities. Corresponding to each quark is an antiquark, with opposite electric charge, etc. (see antiparticles). The theory of quark interactions predicts that isolated quarks can never exist in the free state (under normal conditions of temperature and pressure); they occur only in particular pairs and triplets that form the class of particles called the hadrons. The proton, for example, is composed of one down and two up quarks, the neutron of one up and two down quarks. Quarks are held together through the exchange of massless particles called gluons; these are the carriers of the strong force, one of the four fundamental forces that particles experience.

At present there are tentative suggestions that states of condensed matter, such as the deep interiors of neutron stars, may consist of a soup of free quarks. See also Big Bang theory.

quark

[kwärk]
(particle physics)
One of the hypothetical basic particles, having charges whose magnitudes are one-third or two-thirds of the electron charge, from which many of the elementary particles may, in theory, be built up; for example, nucleons may be formed from three quarks and mesons from quark-antiquark combinations; no experimental evidence for the actual existence of free quarks has been found.

quark

Physics any of a set of six hypothetical elementary particles together with their antiparticles thought to be fundamental units of all baryons and mesons but unable to exist in isolation. The magnitude of their charge is either two thirds or one third of that of the electron
References in periodicals archive ?
In contrast to other baryons, in which the three quarks perform an elaborate dance around each other, a doubly heavy baryon is expected to act like a planetary system, where the two heavy quarks play the role of heavy stars orbiting one around the other, with the lighter quark orbiting around this binary system," Guy Wilkinson, former spokesman of the LHCb collaboration, said in (http://press.
In the beta decay, an excited down quark in the neutron degenerates into a ground state down quark and an excited up and antiup quark pair, [d.
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As the nucleon is a composite system of strong interacting quarks, the amplitude M of the process in Eq.
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Held together by particles called gluons, quarks and their antimatter counterparts, antiquarks, cluster in threes to form baryons (including protons and neutrons) and in pairs to produce mesons (including pions and kaons).
The electron EDM and the quark electric and chromoelectric dipole moments do not arise at the one loop level.
In 1974 three kinds of quarks were known: u-quarks, d-quarks, and s-quarks.
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Physicists have known since the 1960s that protons and neutrons are made up of quarks, as are hundreds of other particles.
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