Dark Matter and Neutrino Masses in a Portalino-like Model

We explore a Portalino-like model of dark matter and neutrino masses in which right-handed neutrino fields connect gauge neutral operators from the Standard Model and Hidden Sector. Neutrino masses are generated via a seesaw-like mechanism that can explain the light active neutrino masses. The model includes a ``Portalino'' state that connects the two sectors via the neutrino portal. Dark Matter in this model consists of a hidden sector Dirac fermion that dominantly freezes-out via resonant annihilations into other hidden sector states, which ultimately results in a population of Portalinos. Due to small mixing in the extended neutrino sector these Portalinos tend to be cosmologically long lived, decaying into Standard Model particles leading to constraints on the model from Big Bang Nucleosynthesis and measurements of the Cosmic Microwave Background radiation. Combining these limits with direct constraints on the size of the Portalino-neutrino mixing and the assumptions of the model the viable mass ranges for the Portalino states are found to be 0.02 eV $\lesssim m_n \lesssim$ 6.4 eV or 489 MeV $\lesssim m_n \lesssim$ TeV. Indirect dark matter signals in the form of highly boosted, mono-energetic Portalinos produced in Dark Matter annihilations provide a target for neutrino telescopes.