Impact of Semi-annihilation of Z3 Symmetric Dark Matter with Radiative   Neutrino Masses
  We investigate a Z3 symmetric model with two-loop radiative neutrino masses. Dark matter in the model is either a Dirac fermion or a complex scalar as a result of an unbroken Z3 symmetry. In addition to standard annihilation processes, semi-annihilation of the dark matter contributes to the relic density. We study the effect of the semi-annihilation in the model and and that those contributions are important to obtain the observed relic density. The experimental signatures in dark matter searches are also discussed, where some of them are expected to be different from the signatures of dark matter in Z2 symmetric models. 
Mayumi Aoki and Takashi Toma
hep-ph astro-ph.HE