baryonantibaryon

A baryonantibaryon refers to a system consisting of a baryon and its corresponding antibaryon. Baryons are three-quark states with baryon number B = +1, while antibaryons are three-antiquark states with B = -1, so a baryonantibaryon pair has total baryon number zero. Classic examples include proton and antiproton, or neutron and antineutron.

In interactions, baryonantibaryon systems are governed primarily by the strong force when they are close together. They can annihilate into multiple mesons or photons, with annihilation cross sections becoming large at low relative momenta. They can also be produced in high-energy collisions, such as in electron–positron annihilation, proton–antiproton collisions, or heavy-ion interactions, where correlated baryon and antibaryon pairs are observed.

The concept of a bound state of a baryon and an antibaryon is historically associated with the term baryonium, used for hypothetical baryon–antibaryon resonances. Throughout the late 20th century, searches for such states occupied experimental and theoretical attention, but no unambiguous, widely accepted bound state has been established. Some reported signals in certain decays of heavy quarkonia have been described as threshold enhancements in baryon–antibaryon channels, though interpretations often remain debated.

The study of baryonantibaryon systems provides insights into nonperturbative quantum chromodynamics, hadron spectroscopy, and matter–antimatter interactions. They illustrate how color confinement and annihilation dynamics shape the behavior of multi-quark systems and their observable final states.

See also: baryon, antibaryon, proton, neutron, baryon number, baryonium, hadron spectroscopy.