Anomaly-free Abelian gauge symmetries with Dirac seesaws

TL;DR

This paper systematically explores Standard Model extensions with anomaly-free U(1) gauge symmetries to generate Dirac neutrino masses via tree-level seesaw mechanisms, considering various constraints and dark matter stability.

Contribution

It provides a comprehensive scan for anomaly-free U(1) symmetries enabling Dirac neutrino masses through type-I and type-II seesaws, including dark matter considerations.

Findings

Identified specific charge assignments satisfying anomaly cancellation.

Demonstrated models with stable dark matter candidates.

Outlined conditions for no extra massless chiral fermions.

Abstract

We perform a systematic analysis of Standard Model extensions with an additional anomaly-free gauge $U(1)$ symmetry, to generate tree-level Dirac neutrino masses. An anomaly-free symmetry demands nontrivial conditions on the charges of the unavoidable new states. An intensive scan was performed, looking for solutions generating neutrino masses by the type-I and type-II tree-level Dirac seesaw mechanism, via operators with dimension 5 and 6, that correspond to active or dark symmetries. Special attention was paid to the cases featuring no extra massless chiral fermions or multicomponent dark matter with unconditional stability.