Neutrino-4 anomaly: oscillations or fluctuations?

TL;DR

This study critically examines the Neutrino-4 anomaly, revealing that the claimed oscillation signal's significance diminishes when accounting for detector effects and is inconsistent with other experimental bounds, casting doubt on the original claim.

Contribution

The paper provides a detailed reanalysis of Neutrino-4 data, incorporating detector energy resolution effects and Monte Carlo simulations, showing the original oscillation signal is less significant and potentially spurious.

Findings

Significance drops from over 3σ to about 2.2σ after refined analysis.

Large mixing values are consistent with no oscillations due to statistical fluctuations.

Neutrino-4 results are in tension with other experimental bounds.

Abstract

We present a deep study of the Neutrino-4 data aimed at finding the statistical significance of the large-mixing short-baseline neutrino oscillation signal claimed by the Neutrino-4 collaboration at more than $3\sigma$. We found that the results of the Neutrino-4 collaboration can be reproduced approximately only by neglecting the effects of the energy resolution of the detector. Including these effects, we found that the best fit is obtained for a mixing that is even larger, close to maximal, but the statistical significance of the short-baseline neutrino oscillation signal is only about $2.7\sigma$ if evaluated with the usual method based on Wilks' theorem. We show that the large Neutrino-4 mixing is in strong tension with the KATRIN, PROSPECT, STEREO, and solar $\nu_{e}$ bounds. Using a more reliable Monte Carlo simulation of a large set of Neutrino-4-like data, we found that the statistical significance of the Neutrino-4 short-baseline neutrino oscillation signal decreases to about $2.2\sigma$. We also show that it is not unlikely to find a best-fit point that has a large mixing, even maximal, in the absence of oscillations. Therefore, we conclude that the claimed Neutrino-4 indication in favor of short-baseline neutrino oscillations with very large mixing is rather doubtful.