KATRIN bound on 3+1 active-sterile neutrino mixing and the reactor antineutrino anomaly

TL;DR

This paper uses KATRIN and other experimental data to set new bounds on sterile neutrino mixing, significantly constraining the parameter space and addressing anomalies in reactor and gallium neutrino experiments.

Contribution

It provides the first bounds from KATRIN on 3+1 sterile neutrino mixing and combines multiple data sources to exclude most of the parameter space suggested by reactor anomalies.

Findings

KATRIN data extend Mainz and Troitsk bounds to smaller Δm²

Combined data exclude most of the reactor anomaly region

Different reactor flux models affect the compatibility with experimental data

Abstract

We present the bounds on 3+1 active-sterile neutrino mixing obtained from the first results of the KATRIN experiment. We show that the KATRIN data extend the Mainz and Troitsk bound to smaller values of $\Delta{m}^2_{41}$ for large mixing and improves the exclusion of the large-$\Delta{m}^2_{41}$ solution of the Huber-Muller reactor antineutrino anomaly. We also show that the combined bound of the Mainz, Troitsk, and KATRIN tritium experiments and the Bugey-3, NEOS, PROSPECT, and DANSS reactor spectral ratio measurements exclude most of the region in the ($\sin^2\!2\vartheta_{ee},\Delta{m}^2_{41}$) plane allowed by the Huber-Muller reactor antineutrino anomaly. Considering two new calculations of the reactor neutrino fluxes, we show that one, that predicts a lower $^{235}\text{U}$ neutrino flux, is in agreement with the tritium and reactor spectral ratio measurements, whereas the other leads to a larger tension than the Huber-Muller prediction. We also show that the combined reactor spectral ratio and tritium measurements disfavor the Neutrino-4 indication of large active-sterile mixing. We finally discuss the constraints on the gallium neutrino anomaly.