  We study the possibility of producing a new kind of nuclear systems which in
addition to ordinary nucleons contain a few antibaryons (antiproton,
antilambda, etc.). The properties of such systems are described within the
relativistic mean-field model by employing G-parity transformed interactions
for antibaryons. Calculations are first done for infinite systems and then for
finite nuclei from He to Pb. It is demonstrated that the presence of a real
antibaryon leads to a strong rearrangement of a target nucleus resulting in a
significant increase of its binding energy and local compression. Noticeable
effects remain even after the antibaryon coupling constants are reduced by
factor 3-4 compared to G-parity motivated values. We have performed detailed
calculations of the antibaryon annihilation rates in the nuclear environment by
applying a kinetic approach. It is shown that due to significant reduction of
the reaction Q-values, the in-medium annihilation rates should be strongly
suppressed leading to relatively long-lived antibaryon-nucleus systems.
Multi-nucleon annihilation channels are analyzed too. We have also estimated
formation probabilities of bound antibaryon-nucleus systems in
antiproton-nucleus reactions and have found that their observation will be
feasible at the future GSI antiproton facility. Several observable signatures
are proposed. The possibility of producing multi-quark-antiquark clusters is
discussed.
