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All quarks are assigned a baryon number of 1 / 3 . Up, charm and top quarks have an electric charge of + 2 / 3 , while the down, strange, and bottom quarks have an electric charge of − 1 / 3 . Antiquarks have the opposite quantum numbers. Quarks are spin- 1 / 2 particles, and thus fermions. Each quark or antiquark ...
As quarks have a baryon number of + + 1 / 3 , and antiquarks of − + 1 / 3 , the pentaquark would have a total baryon number of 1, and thus would be a baryon. Further, because it has five quarks instead of the usual three found in regular baryons (a.k.a. "triquarks"), it is classified as an exotic baryon.
Exotic hadrons are subatomic particles composed of quarks and gluons, but which – unlike "well-known" hadrons such as protons, neutrons and mesons – consist of more than three valence quarks. By contrast, "ordinary" hadrons contain just two or three quarks. Hadrons with explicit valence gluon content would also be considered exotic. [1]
Mesons named with the letter "f" are scalar mesons (as opposed to a pseudo-scalar meson), and mesons named with the letter "a" are axial-vector mesons (as opposed to an ordinary vector meson) a.k.a. an isoscalar vector meson, while the letters "b" and "h" refer to axial-vector mesons with positive parity, negative C-parity, and quantum numbers I G of 1 + and 0 − respectively.
An example would be pentaquarks, consisting of four quarks and one antiquark (qqqqq̅). So far, the only observed exotic baryons are the pentaquarks P c (4380) +, P c (4450) + discovered in 2015, [1] P c (4312) + in 2019 [2] and P Λ ψs (4338) 0 in 2022 by the LHCb collaboration. [3]
These lists detail all known and predicted baryons in total angular momentum J = 1 / 2 and J = 3 / 2 configurations with positive parity. [5]Baryons composed of one type of quark (uuu, ddd, ...) can exist in J = 3 / 2 configuration, but J = 1 / 2 is forbidden by the Pauli exclusion principle.
The current quark mass is also called the mass of the 'naked' quarks. The mass of the current quark is reduced by the term of the constituent quark covering mass.. The current quark mass is a logical consequence of the mathematical formalism of the quantum field theory (QFT), so the idea does not arise from a strictly descriptive report of observations.
, it was made of three strange quarks, and was discovered in 1964. [3] The discovery was a great triumph in the study of quarks, since it was found only after its existence, mass, and decay products had been predicted in 1961 by the American physicist Murray Gell-Mann and, independently, by the Israeli physicist Yuval Ne'eman. Besides the Ω −