We investigate the four-body Coulomb process of low-energy elastic positronium-hydrogen (Ps-H) scattering below the Ps($n=2$) excitation threshold using scattering wave functions that include Hylleraas-type correlation terms. Using the complex Kohn variational method, we compute phase shifts through the ${}^{1,3}H$ wave and obtain highly accurate ${}^{1,3}S$- and ${}^{1,3}P$-wave phase shifts. The complex Kohn variational results compare well to a number of other calculations for this system. We present elastic differential, elastic integrated, and momentum transfer cross sections, and for the singlet, resonances through the ${}^{1}F$ wave. The differential cross section exhibits interesting features, including a change from slightly backward peaked to forward peaked scattering as the energy of the incident positronium increases and rich structure due to multiple resonances near the Ps($n=2$) threshold. We also give a detailed analysis of the scattering lengths and effective ranges using multiple effective range theories.

• Received 15 May 2015

DOI:https://doi.org/10.1103/PhysRevA.92.022713