Dark Matter and the elusive $\mathbf{Z'}$ in a dynamical Inverse Seesaw scenario

TL;DR

This paper explores a dynamical model where a gauged $U(1)$ $B-L$ symmetry leads to an inverse seesaw mechanism for neutrino masses, predicts a dark matter candidate, and discusses the phenomenology of an elusive $Z'$ boson.

Contribution

It introduces a novel dynamical generation of the inverse seesaw mechanism from spontaneous $U(1)$ $B-L$ breaking, predicting a dark sector with a viable dark matter candidate and suppressed $Z'$ interactions.

Findings

A TeV-scale dark matter candidate interacts mainly with the dark sector.

The $Z'$ boson interacts weakly with the Standard Model, reducing direct detection constraints.

The model's collider signatures are discussed, highlighting the elusive nature of the $Z'$.

Abstract

The Inverse Seesaw naturally explains the smallness of neutrino masses via an approximate $B-L$ symmetry broken only by a correspondingly small parameter. In this work the possible dynamical generation of the Inverse Seesaw neutrino mass mechanism from the spontaneous breaking of a gauged $U(1)$ $B-L$ symmetry is investigated. Interestingly, the Inverse Seesaw pattern requires a chiral content such that anomaly cancellation predicts the existence of extra fermions belonging to a dark sector with large, non-trivial, charges under the $U(1)$ $B-L$. We investigate the phenomenology associated to these new states and find that one of them is a viable dark matter candidate with mass around the TeV scale, whose interaction with the Standard Model is mediated by the $Z'$ boson associated to the gauged $U(1)$ $B-L$ symmetry. Given the large charges required for anomaly cancellation in the dark sector, the $B-L$ $Z'$ interacts preferentially with this dark sector rather than with the Standard Model. This suppresses the rate at direct detection searches and thus alleviates the constraints on $Z'$-mediated dark matter relic abundance. The collider phenomenology of this elusive $Z'$ is also discussed.