Effect of positronium formation on elastice+-H scattering at medium energies

Elastic $e^{+}$-H scattering has been investigated by a perturbative approach at medium energies. The effect of the positronium-formation channel on the elastic one has been taken into account explicitly. In the perturbative series, the first term is the solution of the coupled static equation. The conventional perturbative series including the rearrangement channel has also been employed. The effect of the capture channel on the elastic one is found to enhance the cross section near the forward direction. The present results are compared with existing elaborate theoretical predictions.