Abstract
We use a momentum-dependent optical model potential to analyze the annihilation cross sections of the antineutron ¯n on C, Al, Fe, Cu, Ag, Sn, and Pb nuclei for projectile momenta plab ≲500MeV/c. We obtain a good description of annihilation cross section data of Barbina et al. [Nucl. Phys. A 612, 346 (1997)] and of Astrua et al. [Nucl. Phys. A 697, 209 (2002)] which exhibit an interesting dependence of the cross sections on plab as well as on the target mass number A. We also obtain the neutron (n) nonelastic reaction cross sections for the same targets. Comparing the nA reaction cross sections σnArec to the ¯nA annihilation cross sections σ¯nAann, we find that σ¯nAann is significantly larger than σnArec, that is, the σ¯nAann/σnArec cross section ratio lies between the values of about 1.5 to 4.0 in the momentum region where comparison is possible. The dependence of the ¯n annihilation cross section on the projectile charge is also examined in comparison with the antiproton ¯p. Here we predict the ¯pA annihilation cross section on the simplest assumption that both ¯pA and ¯nA interactions have the same nuclear part of the optical potential but differ only in the electrostatic Coulomb interaction. Deviation from a such simple model extrapolation in measurements will provide new information on the difference between ¯nA and ¯pA potentials.
