Positron/Gamma-Ray Signatures of Dark Matter Annihilation and Big-Bang Nucleosynthesis

Abstract

The positron excess observed by the PAMELA experiment may come from dark matter annihilation, if the annihilation cross section is large enough. We show that the dark matter annihilation scenarios to explain the positron excess may also be compatible with the discrepancy of the cosmic lithium abundances between theory and observations. The wino-like neutralino in the supersymmetric standard model is a good example for it. This scenario may be confirmed by Fermi satellite experiment.

5 pages, 4 figures; added references and discussion; included PAMELA data; to appear in PRD; corrected the electromagnetic-emission part, which does not change our conclusion (v4)