DOIAbstract
AbstractWe calculate the fluxes of 511 keV photons from the galactic bulge caused by positrons produced in the decays of relic particles with masses less than 100 MeV. In particular, we tighten the constraints on sterile neutrinos over a large domain of the mass-mixing angle parameter space, where the resulting photon flux would significantly exceed the experimental data. At the same time, the observed photon fluxes can be easily caused by decaying sterile neutrinos in the mass range 1<msterile≲50 MeV with the cosmological abundance typically within 10−9≲Ωsterile≲10−5, assuming that Ωsterile comes entirely from the conversion of active neutrinos in the early universe. Other candidates for decaying relics such as neutral (pseudo)scalar parti...
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