Low-energy D-wave positronium-hydrogen scattering*

We are investigating the four-body Coulomb process of positronium-hydrogen (Ps-H) scattering below the Ps(n=2) excitation threshold using the Kohn variational method and variants. Our Ps-H $^1D$-wave phase shifts compare reasonably well with the close-coupling results [1,2], but our $^3D$-wave phase shifts are appreciably lower. In an attempt to improve the accuracy of these, we are employing a sectors-based approach [3] and the modification of the short-range Hylleraas terms with an exponential in the $r_{12}$ coordinate. We are investigating the use of the Born approximation for higher partial waves. We plan also to present our latest S-wave and P-wave results using the Kohn variational method [4]. \\[4pt] [1] H.R.J. Walters \emph{et al}, Nucl. Instrum. Methods B \textbf{221}, 149-159 (2004).\\[0pt] [2] J. Blackwood \emph{et al}, Phys. Rev. A \textbf{65}, 032517 (2002).\\[0pt] [3] Zong-Chao Yan and Y.K. Ho, Phys. Rev. A \textbf{59}, 2697 (1999).\\[0pt] [4] Denton Woods, S. J. Ward and P. Van Reeth, http://meetings.aps.org/link/BAPS.2013.DAMOP.Q1.122 (and references within).