baryonrich

Baryon-rich is a term used in particle physics and astrophysics to describe matter with a substantial excess of baryons over antibaryons, equivalently with a nonzero net baryon number or finite baryon chemical potential. In such environments, the baryon density is high relative to antibaryons, and the properties of matter are governed by strong interactions at finite density.

In the early universe, conditions soon after baryogenesis left a small but nonzero baryon asymmetry, but as the universe cooled most antibaryons annihilated with baryons, leaving a residual net baryon density. In terrestrial experiments, heavy-ion collisions at lower beam energies aim to create baryon-rich fireballs with a finite baryon chemical potential, enabling study of the quantum chromodynamics phase diagram at finite density. In astrophysics, the cores of neutron stars and the matter in binary neutron star mergers are archetypal baryon-rich environments, potentially hosting hyperon-rich or deconfined quark matter.

Characteristic features include high density of baryons, possible presence of hyperons or strange quark matter, and a stiff or soft equation of state depending on interactions. Finite baryon chemical potential makes lattice quantum chromodynamics calculations difficult due to the sign problem, requiring phenomenological models or extrapolation. Observables include particle yields, net-proton and net-baryon fluctuations, collective flow, and the equation of state inferred from astrophysical data.

Understanding baryon-rich matter helps map the quantum chromodynamics phase diagram, characterize dense nuclear matter in neutron stars, and inform models of heavy-ion collisions and supernova dynamics.