Boosted dark matter via semi-annihilation in a radiative neutrino mass model

Abstract: Dark matter particles can be accelerated by annihilation processes such as semi-annihilations and $n \to m$ ($n > m$) processes when the dark sector is non-minimally extended. Such boosted dark matter can provide a distinctive signature of a non-minimal dark sector, and its experimental detectability has been explored in a model-independent manner in previous work. In this work, we construct an explicit model of boosted dark matter originating from semi-annihilations. A Dirac fermion is identified as the dark matter candidate, which semi-annihilates into a pair of an anti-dark matter particle and a neutrino. The small neutrino masses are also radiatively generated at the two-loop level. Taking into account the relevant experimental and theoretical constraints, we find that the mass of the mediator needs to be $\mathcal{O}(1)~\mathrm{MeV}$ for the elastic scattering with protons, so that the cross section is enhanced to $\mathcal{O}(10^{-36})~\mathrm{cm}^2$, allowing detection in future experiments such as DUNE and DARWIN.