Higgs sector extension of the neutrino minimal standard model with thermal freeze-in production mechanism

TL;DR

This paper explores an extension of the neutrino minimal Standard Model with a Higgs sector modification to facilitate sterile neutrino dark matter production via thermal freeze-in, addressing previous constraints and proposing new leptogenesis scenarios.

Contribution

It introduces a Higgs sector extension of the { u}MSM that enables sterile neutrino dark matter and leptogenesis through thermal freeze-in, overcoming prior observational constraints.

Findings

Thermal freeze-in can produce keV-MeV sterile neutrino dark matter.

The extended model satisfies Lyman-{ a} bounds and X-ray constraints.

TeV-scale singlet scalar is necessary for correct relic densities.

Abstract

The neutrino minimal Standard Model ({\nu}MSM) is the minimum extension of the standard model. In this model, the Dodelson-Widrow mechanism (DW) produces keV sterile neutrino dark matter (DM) and the degenerate GeV heavy Majorana neutrinos lead to leptogenesis. However, the DW mechanism has been ruled out by Lyman-{\alpha} bounds and X-ray constraints. An alternative scenario that evades these constraints has been proposed, where the sterile neutrino DM is generated by the thermal freeze-in mechanism via a singlet scalar. In this paper, we consider a Higgs sector extension of the {\nu}MSM to improve dark matter sectors and leptogenesis scenarios, focusing on the thermal freeze-in production mechanism. We discuss various thermal freeze-in scenarios for the production of keV-MeV sterile neutrino DM with a singlet scalar, and reinvestigate the Lyman-{\alpha} bounds and the X-ray constraints on the parameter regions. Furthermore, we propose thermal freeze-in leptogenesis scenarios in the extended {\nu}MSM. The singlet scalar needs to be TeV scale in order to generate the observed DM relic density and baryon number density with the thermal freeze-in production mechanism.