baryonic

Baryonic refers to baryons, a class of subatomic particles that carry baryon number B = +1. In particle physics, baryons are fermions composed of three quarks, bound by the strong force. The best-known baryons are the proton and neutron, which form the atomic nuclei that make up ordinary matter. Antibaryons are the corresponding antiparticles with B = −1. Particles that are not baryons, such as mesons (quark-antiquark pairs) and leptons, have different quantum numbers.

Baryon number conservation: In most particle interactions, the total baryon number is conserved. This holds in the Standard Model and under ordinary conditions. Certain high-energy or non-perturbative processes in the early universe can violate baryon number, a feature that plays a central role in theories of baryogenesis, the process that generated the matter–antimatter imbalance.

Baryonic matter: The term is used for ordinary matter composed of baryons, primarily protons and neutrons. It makes up atoms and thus stars, planets, and living beings. In cosmology, baryonic matter accounts for about 5 percent of the Universe's energy density, with the remainder consisting of dark matter and dark energy.

Baryonic dark matter and constraints: Proposals of baryonic dark matter (such as compact objects like MACHOs) have been constrained by observations (microlensing and nucleosynthesis), and current evidence indicates that most dark matter is non-baryonic. The study of baryons encompasses nuclear physics, astrophysics, and cosmology, including the processes by which baryons form and interact in stars and galaxies.