In high-energy physics, a pseudoscalar meson is a meson with total spin 0 and odd parity (usually notated as J = 0 ).Pseudoscalar mesons are commonly seen in proton–proton scattering and proton–antiproton annihilation, and include the pion (π), kaon (K), eta (η), and eta prime (η′) particles, whose masses are known with great precision.
Among all of the mesons known to exist, in some sense, the pseudoscalars are the most well studied and understood.
In particle physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks that give rise to the quantum numbers of the hadrons. The quark model underlies "flavor SU(3)", or the Eightfold Way, the successful classification scheme organizing the large number of lighter hadrons that were being discovered starting in the 1950s and continuing through the 1960s. It received experimental verification beginning in the late 1960s and is a valid and effective classification of them to date. The model was independently proposed by physicists Murray Gell-Mann, who dubbed them "quarks" in a concise paper, and George Zweig, who suggested "aces" in a longer manuscript. André Petermann also touched upon the central ideas from 1963 to 1965, without as much quantitative substantiation. Today, the model has essentially been absorbed as a component of the established quantum field theory of strong and electroweak particle interactions, dubbed the Standard Model.
Hadrons are not really "elementary", and can be regarded as bound states of their "valence quarks" and antiquarks, which give rise to the quantum numbers of the hadrons. These quantum numbers are labels identifying the hadrons, and are of two kinds. One set comes from the Poincaré symmetry—J, where J, P and C stand for the total angular momentum, P-symmetry, and C-symmetry, respectively.
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. The American physicist Murray Gell-Mann and the Israeli physicist Yuval Ne'eman independently and simultaneously proposed the idea in 1961.The name comes from Gell-Mann's (1961) paper, "The Eightfold Way: A theory of strong interaction symmetry." It is an allusion to the Noble Eightfold Path of Buddhism and was meant to be a joke.