Antineutron and antiproton nuclear interactions at very low energies

Abstract: Experimental annihilation cross sections of antineutrons and antiprotons at very low energies are compared. Features of Coulomb focusing are observed for $\bar p$ annihilation on protons. Direct comparisons for heavier targets are not straightforward due to lack of overlap between targets and energies of experimental results for $\bar p$ and $\bar n$. Nevertheless, the annihilation cross sections for $\bar n$ on nuclei cannot be described by an optical potential that fits well all the available data on $\bar p$ interactions with nuclei. Comparisons made with the help of this potential reveal in the $\bar n$ data features similar to Coulomb focusing. Direct comparisons between $\bar n$ and $\bar p$ annihilations at very low energies would be possible when $\bar p$ cross sections are measured on the same targets and at the same energies as the available cross sections for $\bar n$. Such measurements may be possible in the foreseeable future.