We calculate, in a systematic way, the enhancement effect on
antiproton-proton and antiproton-nucleus annihilation cross sections at low
energy due to the initial state electrostatic interaction between the
projectile and the target nucleus. This calculation is aimed at future
comparisons between antineutron and antiproton annihilation rates on different
targets, for the extraction of pure isospin channels.Comment: 18 pages, 4 figures (latex format
