antibaryons

Antibaryons are the antiparticles of baryons. Baryons are fermions composed of three quarks; antibaryons consist of three antiquarks and carry a baryon number of -1, opposite to their baryon counterparts, which have +1. They share the same masses and most intrinsic quantum numbers, but their electric charges are opposite the charges of the baryons they correspond to. Common examples include the antiproton, consisting of two anti-up quarks and one anti-down quark, and the antineutron, made of two anti-down quarks and one anti-up quark.

Antibaryons can be produced in high-energy processes, such as proton–proton collisions, heavy-ion collisions, and certain cosmic-ray interactions, where baryon–antibaryon pairs are created to conserve baryon number. Many antibaryons are unstable and decay via weak interactions to lighter antibaryons and mesons; for instance, the anti-Lambda decays to an antiproton and a positive pion with a lifetime of about 2.6×10^-10 seconds. Some light antibaryons, like the antiproton, are effectively stable in vacuum but will annihilate when they meet ordinary matter, releasing energy and pions.

Experimentally, antibaryons are studied in particle accelerators and detectors that track charged particles and identify antiparticles by their charge, momentum, and annihilation signatures. Their observation has been crucial for testing fundamental symmetries and quantum chromodynamics, and for exploring matter–antimatter interactions. The antiparticles of all known baryons have been observed, and their production and behavior inform models of hadronization and the early universe.