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

If the dark matter in our galactic halo consists of weakly interacting massive particles (WIMP's) heavier than the W± boson which have a significant annihilation branch into W± and Z0 pairs, e.g., a Higgsino-like neutralino, a very distinctive feature in the cosmic-ray positron spectrum arises from W+ and Z0 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