Decaying Dark Matter in Supersymmetric SU(5) Models

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 electron/positron 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 electron/positron 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.