Neutrino Portal to Extra Dimensions: Unified Origin of Dark Radiation, Dark Matter, and Neutrino Decay

TL;DR

This paper introduces a unified model with sterile neutrinos in extra dimensions that explains dark radiation, dark matter, and neutrino decay, with testable predictions for cosmological and neutrino experiments.

Contribution

It presents a minimal, testable framework linking sterile neutrinos in large extra dimensions to multiple cosmological and particle physics phenomena.

Findings

KK sterile neutrino as warm dark matter

Relativistic Majoron contributes to Delta Neff

Model predicts observable effects for CMB-S4 and neutrino detectors

Abstract

We propose a unified framework based on sterile neutrinos propagating in large extra dimensions (LED) and coupled to a pseudo-Nambu-Goldstone boson (Majoron) arising from spontaneous lepton number violation. In this setup, the lightest Kaluza-Klein (KK) sterile neutrino serves as warm dark matter, higher KK modes decay invisibly producing a relativistic Majoron contributing to the effective number of neutrino species (Delta Neff), and active neutrinos undergo invisible decay. This model addresses dark radiation, dark matter, and neutrino anomalies within a minimal, testable framework. We present the Boltzmann evolution of relevant species, identify the viable parameter space, and highlight implications for CMB-S4, Lyman-alpha, and neutrino observatories.