Singlet portal extensions of the standard seesaw models to dark sector with local dark symmetry: An alternative to the new minimal standard model

TL;DR

This paper proposes an extension of the standard seesaw model incorporating a dark sector with a local gauge symmetry, successfully explaining cosmological and experimental observations including dark matter, leptogenesis, and Higgs physics.

Contribution

It introduces a minimal seesaw extension with a dark gauge symmetry that unifies dark matter stability and cosmological phenomena.

Findings

Compatible with all current cosmological observations

Predicts Higgs signal strength equal to the SM in certain cases

Accommodates scalar and fermionic dark matter scenarios

Abstract

Assuming dark matter is absolutely stable due to unbroken dark gauge symmetry and singlet operators are portals to the dark sector, we present a simple extension of the standard seesaw model that can accommodate all the cosmological observations as well as terrestrial experiments available as of now, including leptogenesis, extra dark radiation of $\sim 0.08$ (resulting in $N_{\rm eff} = 3.130$ the effective number of neutrino species), Higgs inflation, small and large scale structure formation, and current relic density of scalar DM ($X$). The Higgs signal strength is equal to one as in the SM for unbroken $U(1)_X$ case with a scalar dark matter, but it could be less than one independent of decay channels if the dark matter is a dark sector fermion or if $U(1)_X$ is spontaneously broken, because of a mixing with a new neutral scalar boson in the models.