Abstract
Motivated by recent observations from PAMELA, Fermi and H.E.S.S., we consider dark matter decays in the framework of supersymmetric SU(5) grand unification theories. An SU(5) singlet S is assumed to be the main component of dark matters, which decays into visible particles through dimension six operators suppressed by the grand unification scale. Under certain conditions, S decays dominantly into a pair of sleptons with universal coupling for all generations. Subsequently, electrons and positrons are produced from cascade decays of these sleptons. These cascade decay chains smooth the e++e− spectrum, which permit naturally a good fit to the Fermi-LAT data. The observed positron fraction upturn by PAMELA can be reproduced simultaneously. We have also calculated diffuse gamma-ray spectra due to the e± excesses and compared them with the preliminary Fermi-LAT data from 0.1 GeV to 10 GeV in the region 0°⩽l⩽360°, 10°⩽|b|⩽20°. The photon spectrum of energy above 100 GeV, mainly from final state radiations, may be checked in the near future.
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