Top-down scenariosThe perhaps most exciting scenario describes the production of electrons and positrons via the annihilation of hypothetical particles, most likely WIMP's (weakly interacting massive particles) in the disk and halo of the galaxy that have been proposed to solve the dark matter enigma in the universe. Since early work in the 1990's, numerous studies of this mechanism have been performed, at an increasing rate after the recent data of the PAMELA and ATIC projects were released in 2008. Cosmic-ray electrons and positrons generated by this mechanism are expected to show features in their energy spectrum which depend on the mass and decay modes of the WIMP, but are distinct from the power-law behavior of ordinary cosmic rays, and may extend into an energy region where currently available data are still quite limited.
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