FERMI CONSTRAINS DARK-MATTER ORIGIN OF HIGH-ENERGY POSITRON ANOMALY
- Institut fuer Physik und Astronomie, Universitaet Potsdam, 14476 Potsdam-Golm (Germany)
- Germany
- Physics Department, Ben-Gurion University, Beer-Sheva 84105 (Israel)
Fermi measurements of the high-latitude {gamma}-ray background strongly constrain a decaying-dark-matter origin for the 1-100 GeV Galactic positron anomaly measured with PAMELA. Inverse Compton scattering of the microwave background by the emergent positrons produces a bump in the diffuse 100-200 MeV {gamma}-ray background that would protrude from the observed background at these energies. The positrons are thus constrained to emerge from the decay process at a typical energy between {approx}100 GeV and {approx}250 GeV. By considering only {gamma}-ray emission of the excess positrons and electrons, we derive a minimum diffuse {gamma}-ray flux that, apart from the positron spectrum assumed, is independent of the actual decay modes. Any {gamma}-rays produced directly by the dark-matter decay leads to an additional signal that makes the observational limits more severe. A similar constraint on the energy of emergent positrons from annihilation in dark-matter substructures is argued to exist, according to recent estimates of enhancement in low-mass dark-matter substructures, and improved simulations of such substructure will further sharpen this constraint.
- OSTI ID:
- 21305088
- Journal Information:
- Astrophysical Journal Letters, Vol. 712, Issue 1; Other Information: DOI: 10.1088/2041-8205/712/1/L53; Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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