Antineutron physics

Antineutrons ($\overline{n}$'s) have been used only in the last few years as projectiles for nuclear and particle physics experiments, mainly in the low momentum region. The reason is that, in spite of some undoubted advantages (absence of Coulomb corrections, pure I=1 state for the ($\overline{n}p$) system), the difficulties in obtaining beams of $\overline{n}$'s of suitable intensity and energy definition were overwhelming. The setting-up of suitable beams at BNL and mainly at CERN LEAR (with momentum lower than 400 MeV/c) allowed a first round of interesting experiments. In this review a summary of the most important experimental issues obtained in this field will be presented. They range from studies on the antineutron annihilation dynamics, intended to shed light on the mechanisms responsible for the particles production as well as for the possible formation of quasinuclear nucleon-antinucleon bound states, to meson spectroscopy researches, aiming to identify the existence of new, possibly exotic, resonant structures. Studies on the interactions of antineutrons on nuclei were performed as well, to investigate the nature of the annihilation process (free from Coulomb interactions) inside matter. Finally, some hints about a possible future development of this research subject will be discussed. (201 refs).