Multicomponent dark matter systems and their observation prospects

Conversions and semiannihilations of dark matter (DM) particles in addition to the standard DM annihilations are considered in a three-component DM system. We find that the relic abundance of DM can be very sensitive to these nonstandard DM annihilation processes, which has been recently found for two-component DM systems. To consider a concrete model of a three-component DM system, we extend the radiative seesaw model of Ma by adding a Majorana fermion chi and a real scalar boson [varphi], to obtain a Z sub(2) x (ProQuest: Formulae and/or non-USASCII text omitted) DM stabilizing symmetry, where we assume that the DM particles are the inert Higgs boson, chi and [varphi]. It is shown how the allowed parameter space, obtained previously in the absence of chi and [varphi], changes. The semiannihilation process in this model produces monochromatic neutrinos. The observation rate of these monochromatic neutrinos from the Sun at IceCube is estimated. Observations of high-energy monochromatic neutrinos from the Sun may indicate a multicomponent DM system.