A testable hidden-sector model for Dark Matter and neutrino masses

TL;DR

This paper proposes a minimal hidden-sector extension of the Standard Model that explains neutrino masses and dark matter, with testable predictions for cosmology and particle physics experiments.

Contribution

It introduces a new anomaly-free hidden sector model that naturally includes dark matter and neutrino masses without extra symmetries, and explores its phenomenology.

Findings

The model can account for dark matter relic abundance.

It predicts additional relativistic degrees of freedom in the early Universe.

The model can alleviate the Hubble constant tension.

Abstract

We consider a minimal extension of the Standard Model with a hidden sector charged under a dark local $U(1)'$ gauge group, accounting simultaneously for light neutrino masses and the observed Dark Matter relic abundance. The model contains two copies of right-handed neutrinos which give rise to light neutrino-masses via an extended seesaw mechanism. The presence of a stable Dark-Matter candidate and a massless state naturally arise by requiring the simplest anomaly-free particle content without introducing any extra symmetries. We investigate the phenomenology of the hidden sector considering the $U(1)'$ breaking scale of the order of the electroweak scale. Confronting the thermal history of this hidden-sector model with existing and future constraints from collider, direct and indirect detection experiments provides various possibilities of probing the model in complementary ways as every particle of the dark sector plays a specific cosmological role. Across the identified viable parameter space, a large region predicts a sizable contribution to the effective relativistic degrees-of-freedom in the early Universe that allows to alleviate the recently reported tension between late and early measurements of the Hubble constant.