Distinctive positron feature from particle dark-matter annihilations in the galatic halo

If the dark matter in our galactic halo consists of weakly interacting massive particles (WIMP's) heavier than the $W^{\pm }$ boson which have a significant annihilation branch into $W^{\pm }$ and $Z^0$ pairs, e.g., a Higgsino-like neutralino, a very distinctive feature in the cosmic-ray positron spectrum arises from $W^{+}$ and $Z^0$ decays. Because of inherent astrophysical uncertainties such a signal is by no means guaranteed even if heavy WIMP's do comprise the galactic halo. However, the positron signature is virtually a "smoking gun" for particle dark matter in the halo and thus worthy of note.