Coherent η-meson production in the reaction π^{-}+^{3}He→η+t

Abstract

The reaction ${\pi }^{\mathrm{-}}$ ${+}^3$He→η+t has been observed by detecting η→2γ decays. The observed forward-angle cross sections vary from ∼100 μb/sr at 680 MeV/c to ∼2 μb/sr at 590 MeV/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 p+d→η${+}^3$He measured at similar η center-of-mass energies.