baryon

A baryon is a fermionic hadron composed of three quarks bound together by the strong force. All baryons carry a baryon number B = 1 and are color-neutral, forming a color singlet in quantum chromodynamics. They are one of the two families of hadrons, the other being mesons, which consist of a quark–antiquark pair.

In the quark model, baryons are built from up, down, strange, and heavier quarks. The proton is made of two up quarks and one down quark (uud), while the neutron consists of one up and two down quarks (udd). Other known baryons include the Lambda (uds), Sigma (uus, uds, or dss), Xi (dss or uss), and the Omega minus (sss). Ground-state baryons typically have spin 1/2, but some excited states, such as the Delta and certain Sigma*, Xi*, and the Omega−, have spin 3/2.

Baryon masses are around 1 GeV/c^2, with most of that mass arising from the energy of the strong interaction rather than the intrinsic quark masses. Baryons are confined by the strong force and cannot be isolated; they interact through the strong, electromagnetic, and weak forces. They are produced in high-energy collisions and in cosmic processes, and they participate in various processes that conserve baryon number.

The lightest baryons, protons and neutrons, make up atomic nuclei and thus ordinary matter. Heavier baryons typically decay via the weak interaction on very short timescales. Baryons play a central role in particle physics, nuclear physics, and cosmology, including topics such as baryogenesis in the early universe and the structure of dense astrophysical objects like neutron stars.