Galactic positrons from Z0 decay

The positron excess below 10 GeV in the Galactic cosmic rays is shown to closely resemble the expected spectrum from sub-relativistic Z0 decay. The possibility is critically examined that the Galactic dark matter is composed of neutralinos that are just above the half the Z0 mass, and that the excess positrons derive from “decay” of virtual Z0 bosons produced when the neutralinos annihilate. While this mechanism provides a very good fit for energies below 10 GeV, at higher energy it seems to disagree with the data given conventional assumptions about propagation.