Loop Dominated Signals from Neutrino Portal Dark Matter

We study scenarios where loop processes give the dominant contributions to dark matter decay or annihilation despite the presence of tree-level channels. We illustrate this possibility in a specific model where dark matter is part of a hidden sector that communicates with the Standard Model sector via a heavy neutrino portal. We explain the underpinning rationale for how loop processes mediated by the portal neutrinos can parametrically dominate over tree-level decay channels, and we demonstrate that this qualitatively changes the indirect detection signals in positrons, neutrinos, and gamma rays.