  First experimental results on photoproduction of eta-mesic nuclei are
analyzed. In an experiment performed at the 1 GeV electron synchrotron of the
Lebedev Physical Institute, correlated pi+n pairs arising from the reaction
gamma + 12C -> N + eta(A-1) -> N + pi+ + n + (A-2) and flying transversely to
the photon beam have been observed. When the photon energy exceeds the
eta-meson production threshold, a distribution of the pi+n pairs over their
total energy is found to have a peak in the subthreshold region of the
internal-conversion process eta p -> pi+ n which signals about formation of
eta-mesic nuclei.
