Semiannihilation of fermionic dark matter

Abstract

The continued nonobservation of events emanating from dark matter annihilations in various direct and indirect detection experiments calls into question the mechanism for determining the relic density of a weakly interacting massive particle. However, if the relic density is determined primarily by a semiannihilation process, as opposed to the usual annihilation, this tension can be ameliorated. Here, we investigate a ${Z}_{3}$ symmetric effective field theory incorporating a fermionic dark matter that semiannihilates to right-handed neutrinos. The dynamics of the right-handed neutrinos and the impact of its late decays are also scrutinized while obtaining the correct dark matter relic. Finally, indirect detection bounds on the semiannihilation cross sections are drawn from the gamma-ray observations in the direction of dwarf spheroidal galaxies (Fermi-LAT), and including the projections obtained for the H.E.S.S. and the CTA detectors.