Low-temperature antihydrogen-atom scattering
  A simple method to include the strong force in atom-antiatom scattering is presented. It is based on the strong-force scatteringn length between the nucleon and antinucleon. Using this method elastic and annihilation cross sections are calculated for hydrogen-antihydrogen and helium-antihydrogen scattering. The results are compared to first-order perturbation theory using a pseudo potential. The pseudo-potential approach works fairly well for hydrogen-antihydrogen scattering, but fails for helium-antihydrogen scattering where strong-force effects are more prominent. 
S Jonsell