Coherent eta -meson production in the reaction pi -+3He--> eta +t.

The reaction {pi}{sup {minus}}+{sup 3}He{r arrow}{eta}+{ital t} has been observed by detecting {eta}{r arrow}2{gamma} decays. The observed forward-angle cross sections vary from {similar to}100 {mu}b/sr at 680 MeV/{ital c} to {similar to}2 {mu}b/sr at 590 MeV/{ital c}. Distorted-wave impulse-approximation calculations reproduce the shape but underestimate the magnitude of the observed cross section. These cross sections are approximately 100 times larger than those for the reaction {ital p}+{ital d}{r arrow}{eta}+{sup 3}He measured at similar {eta} center-of-mass energies.