Resonant antihydrogen formation in antiproton-positronium collisions

We study the influence of narrow resonances on antihydrogen formation cross sections via the three-body reaction (p) over bar + Ps* -> (H) over bar* + e(-). The latter is of interest for the gravitational behavior of antihydrogen at rest experiment that will be performed at CERN in the near future. The complex scaling method is employed to compute the positions and widths of these resonances, whereas the Kohn-variational principle is used for the determination of the scattering cross sections. A very good agreement is found with available theoretical results. The impact of these resonances on the cross section is analyzed.