Energy-dependent Ps-He momentum-transfer cross section at low energies

Abstract

Positronium (Ps)-He scattering presents one of the few opportunities for both theory and experiment to tackle the fundamental interactions of Ps with ordinary matter. Below the dissociation energy of $6.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, experimental and theoretical work has struggled to find agreement on the strength of this interaction as measured by the momentum-transfer cross section $({\ensuremath{\sigma}}_{m})$. Here, we present work utilizing the Doppler broadening technique with an age-momentum correlation apparatus. This work demonstrates a strong energy dependence for this cross section at energies below $1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and is consistent with previous experimental results.