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While the quark model is derivable from the theory of quantum chromodynamics, the structure of hadrons is more complicated than this model allows. The full quantum mechanical wavefunction of any hadron must include virtual quark pairs as well as virtual gluons, and allows for a variety of mixings. There may be hadrons which lie outside the ...
The discovery finally convinced the physics community of the quark model's validity. [35] In the following years a number of suggestions appeared for extending the quark model to six quarks. Of these, the 1975 paper by Haim Harari [41] was the first to coin the terms top and bottom for the additional quarks. [42]
The strong force is described by quantum chromodynamics (QCD), a part of the Standard Model of particle physics. Mathematically, QCD is a non-abelian gauge theory based on a local (gauge) symmetry group called SU(3). The force carrier particle of the strong interaction is the gluon, a massless gauge boson.
[b] In a pentaquark, the colours also need to cancel out, and the only feasible combination is to have one quark with one colour (e.g. red), one quark with a second colour (e.g. green), two quarks with the third colour (e.g. blue), and one antiquark to counteract the surplus colour (e.g. antiblue). [11]
According to the quark model, [8] the properties of hadrons are primarily determined by their so-called valence quarks. For example, a proton is composed of two up quarks (each with electric charge + + 2 ⁄ 3, for a total of + 4 ⁄ 3 together) and one down quark (with electric charge − + 1 ⁄ 3). Adding these together yields the proton ...
For example, the up quark has T 3 = + + 1 / 2 and the down quark has T 3 = − + 1 / 2 . A quark never decays through the weak interaction into a quark of the same T 3: Quarks with a T 3 of + + 1 / 2 only decay into quarks with a T 3 of − + 1 / 2 and conversely. π + decay through the weak interaction
In physics, the eightfold way is an organizational scheme for a class of subatomic particles known as hadrons that led to the development of the quark model. Both the American physicist Murray Gell-Mann and the Israeli physicist Yuval Ne'eman independently and simultaneously proposed the idea in 1961.
Other effective theories are heavy quark effective theory (which expands around heavy quark mass near infinity), and soft-collinear effective theory (which expands around large ratios of energy scales). In addition to effective theories, models like the Nambu–Jona-Lasinio model and the chiral model are often used when discussing general features.