Updated global analysis of neutrino oscillations in the presence of eV-scale sterile neutrinos

TL;DR

This paper analyzes global neutrino oscillation data within a 3+1 sterile neutrino framework, finding support for some anomalies but excluding sterile neutrino explanations for others with high confidence.

Contribution

It provides a comprehensive global analysis of sterile neutrino effects, incorporating recent experimental data and robustly constraining sterile neutrino parameters.

Findings

Reactor experiments support sterile neutrino explanation of reactor anomaly.

Global data favor sterile neutrino oscillations at 3σ for Δm²₄₁ ≈ 1.3 eV².

LSND anomaly is excluded at 4.7σ under sterile neutrino hypothesis.

Abstract

We discuss the possibility to explain the anomalies in short-baseline neutrino oscillation experiments in terms of sterile neutrinos. We work in a 3+1 framework and pay special attention to recent new data from reactor experiments, IceCube and MINOS+. We find that results from the DANSS and NEOS reactor experiments support the sterile neutrino explanation of the reactor anomaly, based on an analysis that relies solely on the relative comparison of measured reactor spectra. Global data from the $\nu_e$ disappearance channel favour sterile neutrino oscillations at the $3\sigma$ level with $\Delta m^2_{41} \approx 1.3$ eV$^2$ and $|U_{e4}| \approx 0.1$, even without any assumptions on predicted reactor fluxes. In contrast, the anomalies in the $\nu_e$ appearance channel (dominated by LSND) are in strong tension with improved bounds on $\nu_\mu$ disappearance, mostly driven by MINOS+ and IceCube. Under the sterile neutrino oscillation hypothesis, the p-value for those data sets being consistent is less than $2.6\times 10^{-6}$. Therefore, an explanation of the LSND anomaly in terms of sterile neutrino oscillations in the 3+1 scenario is excluded at the $4.7\sigma$ level. This result is robust with respect to variations in the analysis and used data, in particular it depends neither on the theoretically predicted reactor neutrino fluxes, nor on constraints from any single experiment. Irrespective of the anomalies, we provide updated constraints on the allowed mixing strengths $|U_{\alpha 4}|$ ($\alpha = e,\mu,\tau$) of active neutrinos with a fourth neutrino mass state in the eV range.