Antineutron-nucleus annihilation cross sections below 400 MeV/c

Antineutron annihilation cross sections on C, Al, Cu, Ag, Sn and Pb targets were measured in the momentum range 50-400 MeV/c. The full set of data is very well described by a parameterization in which the target mass number and momentum dependence are factorized. The A dependence is, within 2%, consistent with a A(2/3) scaling law, indicating a pure surface process. The momentum dependence is, within 20%, consistent with that expected from a properly averaged contribution of the elementary cross section for (n) over barp and (n) over barn annihilation, indicating that the process is due to the interaction with single nucleons on the surface.