Monochromatic neutrinos from scotogenic dark matter

TL;DR

This paper explores a variation of the scotogenic model where dark matter particles predominantly annihilate into neutrino pairs, consistent with observed relic abundance and potentially addressing the lithium problem.

Contribution

It introduces a new variant of the scotogenic model with pseudo-Dirac fermions and distinct neutrino-dominated annihilation phenomenology.

Findings

Dark matter candidate is a fermion singlet with 0.1-1 TeV mass.

Near-threshold annihilation into neutrino pairs with 90% branching ratio.

Model aligns with relic abundance, neutrino data, and direct search bounds.

Abstract

The scotogenic model defines a framework for radiative neutrino masses and provides a viable dark matter candidate. Since the scotogenic dark matter is leptophilic, indirect searches appear as an especially interesting possibility. Here we propose a simple variation of the model with a very distinct phenomenology. The scotogenic fermion singlets are naturally grouped into pseudo-Dirac pairs of mass of 0.1-1 TeV. We show that the lightest one constitutes a dark matter candidate that near threshold annihilates with a 90% branching ratio into neutrino pairs. The model gives the observed relic abundance consistently with the bounds from direct searches and with all neutrino and charged lepton data. We also show that, for a sub-MeV dark matter particle, the model suggests a scenario that could address the lithium problem.