Baryons

A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 e (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an electron (the proton-to-electron mass ratio). Protons and neutrons, each with a mass of approximately one dalton, are jointly referred to as nucleons (particles present in atomic nuclei).

A neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The neutron was discovered by James Chadwick in 1932, leading to the discovery of nuclear fission in 1938, the first self-sustaining nuclear reactor (Chicago Pile-1, 1942), and the first nuclear weapon (Trinity, 1945).

thumb|An atomic nucleus is shown here as a compact bundle of the two types of nucleons, [[protons (red) and neutrons (blue). In this picture, the protons and neutrons are shown as distinct, which is the conventional view in chemistry, for example. But in an actual nucleus, as understood by modern nuclear physics, the nucleons are partially delocalized and organize themselves according to the laws of quantum chromodynamics.]] In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus define

In particle physics, a baryon is a type of composite subatomic particle that contains an odd number of valence quarks, conventionally three. 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-integer spin.

The antiproton, , (pronounced p-bar) is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy.

The antineutron is the antiparticle of the neutron with symbol . It differs from the neutron only in that some of its properties have equal magnitude but opposite sign. It has the same mass as the neutron, and no net electric charge, but has opposite baryon number (+1 for neutron, −1 for the antineutron). This is because the antineutron is composed of antiquarks, while neutrons are composed of quarks. The antineutron consists of one up antiquark and two down antiquarks.

one third of the difference between the number of quarks and antiquarks in a system

In particle physics, a hyperon is any baryon containing one or more strange quarks, but no charm, bottom, or top quarks. This form of matter may exist in a stable form within the core of some neutron stars. Hyperons are sometimes generically represented by the symbol Y.

In nuclear physics and particle physics, isospin is a quantum number related to the up- and down quark content of the particle. Isospin is also known as isobaric spin or isotopic spin. Isospin symmetry is a subset of the flavour symmetry seen more broadly in the interactions of baryons and mesons.

A pentaquark is a subatomic particle, consisting of four quarks and one antiquark bound together. Evidence for the existence of pentaquarks has been found in decays of the Bottom lambda baryon.

Family of subatomic particles

baryon made of specific quark combinations

In physical cosmology, baryogenesis (also known as baryosynthesis) is the physical process that is hypothesized to have taken place during the early universe to produce baryonic asymmetry, the observation that only matter (baryons) and not antimatter (antibaryons) is detected in the universe (other than in cosmic ray collisions). Since it is assumed in cosmology that the particles we see were created using the same physics we measure today, and in particle physics experiments today matter and antimatter are always symmetric, the dominance of matter over antimatter is unexplained.

subatomic hadron particle

baryon made of specific quark combinations

subatomic particle

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type of hadron (bound states of quarks and gluons) with half-integer spin, but have a quark content different to the three quarks (qqq) present in conventional baryons

fluctuations in the density of the visible baryonic matter of the universe, caused by acoustic density waves in the primordial plasma of the early universe

dark matter composed of baryons

In particle physics, hexaquarks, alternatively known as sexaquarks, are a large family of hypothetical particles, each particle consisting of six quarks or antiquarks of any flavours. Six constituent quarks in any of several combinations could yield a colour charge of zero; for example a hexaquark might contain either six quarks, resembling two baryons bound together (a dibaryon), or three quarks and three antiquarks. Once formed, dibaryons are predicted to be fairly stable by the standards of particle physics.

discrepency between observed and predicted amounts of ordinary matter