Near-threshold production of η mesons

Abstract

It is shown that the striking energy variation in the pd${\ensuremath{\rightarrow}}^{3}$He \ensuremath{\eta} cross section near threshold is probably due to a final state interaction associated with a large (complex) \ensuremath{\eta}${\mathrm{\ensuremath{-}}}^{3}$He scattering length. The consequences of this hypothesis are studied for the production of the meson in the \ensuremath{\eta}${\mathrm{\ensuremath{-}}}^{4}$He and \ensuremath{\eta}${\mathrm{\ensuremath{-}}}^{7}$Be channels.