Low-Energy Antinucleon-Nucleus Interaction Revisited

Abstract

Annihilation cross sections of antiprotons and antineutrons on the proton between 50 and 400 MeV/c show Coulomb focusing below 200 MeV/c and almost no charge-dependence above 200 MeV/c. Similar comparisons for heavier targets are not possible for lack of overlap between nuclear targets studied with $\bar{p}$ and $\bar{n}$ beams. Interpolating between $\bar{p}$-nucleus annihilation cross sections with the help of an optical potential to compare with $\bar{n}$-nucleus annihilation cross sections reveal unexpected features of Coulomb interactions in the latter. Direct comparisons between $\bar{n}$-nucleus and $\bar{p}$-nucleus annihilations at very low energies could be possible if $\bar{p}$ 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 feasible in the foreseeable future.

Comments: 8 pages, 4 figures, to appear in Proceedings of the International Conference on Exotic Atoms and Related Topics (EXA 2014), Vienna, Austria, 15-19 September 2014