Freeze-In Dark Matter within the Seesaw mechanism

TL;DR

This paper demonstrates that the minimal Type-I Seesaw mechanism can produce keV sterile neutrino dark matter through freeze-in decay of heavier leptons, aligning with cosmological and phenomenological constraints.

Contribution

It shows how the Type-I Seesaw can naturally generate sterile neutrino dark matter via freeze-in, linking neutrino physics with dark matter production.

Findings

Sterile neutrino dark matter can be produced by decay of heavy neutral leptons.

The model's parameter space aligns with relic abundance and structure formation constraints.

An approximate lepton number symmetry emerges in the viable parameter region.

Abstract

We show that the minimal Type-I Seesaw mechanism can successfully account for the observed dark matter abundance in the form of a keV sterile neutrino. This population can be produced by the decay of the heavier neutral leptons, with masses above the Higgs mass scale, while they are in thermal equilibrium in the early Universe (freeze-in). Moreover, the implementation of the relevant phenomenological constraints (relic abundance, indirect detection and structure formation) on this model automatically selects a region of the parameter space featuring an approximate lepton number symmetry.