A sterile neutrino scenario constrained by experiments and cosmology

TL;DR

The paper analyzes a 3 active + 1 sterile neutrino framework to reconcile solar, atmospheric, and LSND anomalies, showing that with Nν<4 all six mixings are tightly constrained and only the small-angle MSW solar solution is viable; Majorana masses face stringent 0νββ-imposed mass bounds, limiting hot dark matter contributions. If Nν≥4, sterile states relax constraints, allowing all solar solutions and the possibility that sterile neutrinos contribute to hot dark matter, potentially yielding observable 0νββ decays. The study combines four-flavor oscillation formalism with reactor/accelerator data and cosmological constraints (BBN) to map viable regions of mixing angles and mass splittings, highlighting how laboratory and cosmological data jointly constrain beyond-Standard-Model neutrino scenarios. The results inform the viability of sterile neutrinos and set expectations for future experiments (e.g., Super-Kamiokande/SNO and 0νββ searches) to probe these scenarios.

Abstract

We discuss a model in which three active and one sterile neutrino account for the solar, the atmospheric and the LSND neutrino anomalies. It is shown that if $N_ν<4$ then these and other experiments and big bang nucleosynthesis constrain all the mixing angles severely, and allow only the small-angle MSW solution. If these neutrinos are of Majorana type, then negative results of neutrinoless double beta decay experiments imply that the total mass of neutrinos is not sufficient to account for all the hot dark matter components.