Neutrino Dipole Portal

TL;DR

The neutrino dipole portal (NDP) extends the Standard Model by coupling active neutrinos to heavy neutral leptons through a magnetic moment, enabling diverse experimental and astrophysical tests for new physics.

Contribution

This review comprehensively discusses the theoretical basis, mechanisms, and experimental constraints of the NDP, highlighting its broad testability across multiple scientific domains.

Findings

Current bounds from collider and astrophysical data

Potential for discovery in next-generation experiments

NDP offers a minimal, testable extension of the Standard Model

Abstract

The neutrino dipole portal (NDP) is a minimal and predictive extension of the Standard Model, in which a transition magnetic moment operator couples an active neutrino to a heavy neutral lepton via the electromagnetic field. This higher-dimensional interaction gives rise to distinctive processes such as neutrino up-scattering, radiative decays, meson transitions, and modifications of recoil spectra, offering multiple avenues for discovery. In this review, we discuss the theoretical foundations of the NDP, its ultraviolet completions, and the associated production and decay mechanisms across laboratory, astrophysical, and cosmological settings. Current constraints arise from accelerator searches, recoil-based detectors, collider studies, and high energy neutrino observatories, complemented by robust bounds from Big Bang Nucleosynthesis, the Cosmic Microwave Background, and supernova cooling. Future experimental and observational efforts, including next-generation neutrino experiments, multi-ton dark matter detectors, and improved cosmological and astrophysical probes, are anticipated to test the remaining allowed regions. The NDP thus provides a simple, well-motivated, and broadly testable framework at the intersection of particle physics, astrophysics, and cosmology.