The contribution to the antimatter flux from individual dark matter substructures

Abstract

The local antimatter fluxes induced by an individual dark matter (DM) substructure can be significantly dependent on the proper motion of the source. We derive analytic solutions to the propagation equation for time-dependent positron and antiproton primary sources, finding that the static limit is a fair approximation only for very high energy particles and nearby sources. We discuss weakly interacting massive particle (WIMP) models fitting the PAMELA positron excess and the FERMI all-electron data. We show that, for a single non-static DM point-source, one cannot extract from the data, in a unique way, model independent particle physics observables, such as the WIMP mass, the pair annihilation cross section, and the annihilation yield. The gamma-ray emission associated to WIMP models inducing a significant local flux of positrons or antiprotons is found to be compatible with EGRET measurements, but it can be definitely singled out with the FERMI-LAT telescope.