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.