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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.
Because mesons are composed of quark subparticles, they have a meaningful physical size, a diameter of roughly one femtometre (10 −15 m), [1] which is about 0.6 times the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few tenths of a nanosecond.
Similar decay products exist for the other quark–lepton generations. In these reactions, neither the lepton number (L) nor the baryon number (B) is separately conserved, but the combination B − L is. Different branching ratios between the X boson and its antiparticle (as is the case with the K-meson) would explain baryogenesis. For instance ...
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.
The best known baryons are protons and neutrons, which make up most of the mass of the visible matter in the universe, whereas electrons, the other major component of atoms, are leptons. Each baryon has a corresponding antiparticle , known as an antibaryon, in which quarks are replaced by their corresponding antiquarks.
In particle physics, a baryon is a type of composite subatomic particle that contains an odd number of valence quarks, conventionally three. [1] Protons and neutrons are examples of baryons; because baryons are composed of quarks, they belong to the hadron family of particles. Baryons are also classified as fermions because they have half ...
Three quarks of different colors, giving a baryon with baryon number +1, Three antiquarks of different anticolors, giving an antibaryon with baryon number −1. The baryon number was defined long before the quark model was established, so rather than changing the definitions, particle physicists simply gave quarks one third the baryon number.
According to the 2022 Particle Physics Review, the charmed quark has a mass of 1.27 ± 0.02 GeV/c 2, [b] a charge of + 2 / 3 e, and a charm of +1. [10] The charm quark is more massive than the strange quark: the ratio between the masses of the two is about 11.76 +0.05 −0.10. [10] The CKM matrix describes the weak interaction of quarks ...