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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.
All mesons are unstable, with the longest-lived lasting for only a few tenths of a nanosecond. Heavier mesons decay to lighter mesons and ultimately to stable electrons , neutrinos and photons . Outside the nucleus, mesons appear in nature only as short-lived products of very high-energy collisions between particles made of quarks, such as ...
Because mesons have integer spin (0 or 1) and are not themselves elementary particles, they are classified as "composite" bosons, although being made of elementary fermions. Examples of mesons include the pion, kaon, and the J/ψ. In quantum hadrodynamics, mesons mediate the residual strong force between nucleons.
A strange particle is an elementary particle with a strangeness quantum number different from zero. Strange particles are members of a large family of elementary particles carrying the quantum number of strangeness , including several cases where the quantum number is hidden in a strange/anti-strange pair, for example in the ϕ meson .
The strange quark or s quark (from its symbol, s) is the third lightest of all quarks, a type of elementary particle. Strange quarks are found in subatomic particles called hadrons. Examples of hadrons containing strange quarks include kaons (K), strange D mesons (D s), Sigma baryons (Σ), and other strange particles.
Exotic mesons; Exotic baryons; Glueball, hypothetical particle that consist of only gluons. Quark bound states beyond the pentaquark, like hexaquarks and heptaquarks. Leptoquark, hypothetical particles that are neither bosons or fermions but carry lepton and baryon numbers. Magnetic monopole is a generic name for particles with non-zero ...
It was thought that the initial states should also have different parities, and hence be two distinct particles. However, with increasingly precise measurements, no difference was found between the masses and lifetimes of each, respectively, indicating that they are the same particle. This was known as the τ–θ puzzle.
In the next few years, several other charmed particles, including the D meson and the charmed strange mesons, were found. In the 21st century, a baryon containing two charm quarks has been found. There is recent evidence that intrinsic charm quarks exist in the proton, and the coupling of the charm quark and the Higgs boson has been studied.