  In previous papers we have proposed a method for the ab initio calculation of
fully differential cross-sections for electron scattering in liquids and
applied it to liquid argon, xenon and krypton. In this paper, we extend the
procedure to the consideration of positron scattering in liquid helium, which
is complicated by the annihilation process as well as the fact that the
electron definition for the region "owned" by a target atom used previously
does not have a positron analogue. We explore several physically motivated
definitions to obtain effective positron scattering in the dense fluid. We find
that our calculations of a pure helium system cannot precisely match
experimental measurements, however by including a small admixture (<0.1%) of an
impurity, we can obtain reasonable agreement in the dense gas phase. In
contrast, our calculations do not match well to the liquid phase measurements.
This provides motivation to explore further multiple scattering effects in the
theory.
