Variational close-coupling calculation for positron-hydrogen scattering at low energies

The S-wave (L=0) and P-wave (L=1) phase shifts and the S-wave and P-wave elastic and positronium-formation cross sections for positron scattering from hydrogen at energies below the first excitation threshold are calculated in the close-coupling approximation, using the algebraic variational method. Four target-state coupling schemes (H 1s--Ps 1s, H 1s-- H 2s--Ps 1s, H 1s--H 2s--H 2p--Ps 1s, and H 1s--H 2s--H 2p{}--Ps 1s) have been considered for the calculation. It is found that the H 2p{} target channel significantly affects the S-wave positronium-formation cross sections.