Warm Dark Matter in B-L Inverse Seesaw

TL;DR

This paper proposes a B-L extended Standard Model framework where keV-scale singlet fermions serve as warm dark matter candidates, avoiding X-ray constraints and addressing over-abundance via moduli decay and reheating processes.

Contribution

It introduces a novel warm dark matter candidate within a B-L inverse seesaw model that avoids active neutrino mixing constraints and explores production mechanisms during reheating.

Findings

Warm dark matter candidate can be produced via moduli decay.

Over-abundance can be mitigated with low reheat temperature.

Constraints on moduli decay branching ratios for relic abundance.

Abstract

We show that a standard model gauge singlet fermion field, with mass of order keV or larger, and involved in the inverse seesaw mechanism of light neutrino mass generation, can be a good warm dark matter candidate. Our framework is based on B-L extension of the Standard Model. The construction ensures the absence of any mixing between active neutrinos and the aforementioned dark matter field. This circumvents the usual constraints on the mass of warm dark matter imposed by X-ray observations. We show that over-abundance of thermally produced warm dark matter (which nevertheless do not reach chemical equilibrium) can be reduced to an acceptable range in the presence of a moduli field decaying into radiation --- though only when the reheat temperature is low enough. Our warm dark matter candidate can also be produced directly from the decay of the moduli field during reheating. In this case, obtaining the right amount of relic abundance, while keeping the reheat temperature high enough as to be consistent with Big Bang nucleosynthesis bounds, places constraints on the branching ratio for the decay of the moduli field into dark matter.