Near-Threshold Production of $η$-Mesons

Abstract

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

9 pages + 2 postscript figures