A Minimal Dark $U(1)_D$ Framework for Inverse Seesaw Neutrino Masses and Dark Matter
We propose a minimal framework based on a dark $U(1)_D$ gauge symmetry that simultaneously accounts for neutrino masses and dark matter within an inverse seesaw realization. In this setup, the smallness of light neutrino masses is controlled, suppressed by a lepton-number violating parameter $μ$, which arises dynamically by dark field corrections rather than being introduced by hand. The limit $μ\to 0$ restores lepton number symmetry, ensuring its, thus neutrino mass, smallness in the sense of 't Hooft naturalness. We analyze the neutrino mass matrix and active-sterile mixing, highlighting their impact on non-unitarity and charged lepton flavor violation. The model is consistent with current experimental constraints while allowing potentially observable signals, such as $μ\to e γ$. The dark $U(1)_D$ symmetry stabilizes the dark matter candidate and links the neutrino and dark sectors. Viable parameter regions satisfying dark matter relic density, direct detection, and collider bounds are identified. This framework provides a minimal and predictive realization of neutrino mass generation and dark matter stability with a naturally small $μ$ parameter.