Search for eV Sterile Neutrinos -- The STEREO Experiment [Blois 2019]

TL;DR

The STEREO experiment tests for light sterile neutrinos by measuring reactor antineutrino spectra at multiple baselines, finding no evidence for oscillations and rejecting the Reactor Antineutrino Anomaly at 99% confidence.

Contribution

It provides a direct, flux-independent search for sterile neutrinos using multiple detectors near a research reactor, setting new constraints on sterile neutrino parameters.

Findings

No evidence of sterile neutrino oscillations was observed.

The null oscillation hypothesis is compatible with the data.

The Reactor Antineutrino Anomaly is rejected at 99% confidence.

Abstract

The STEREO experiment is designed to test the hypothesis of light sterile neutrinos being the cause of the Reactor Antineutrino Anomaly. It measures the antineutrino energy spectrum from the compact core of the ILL research reactor in six identical detector cells covering baselines between 9 and 11 m. Results from 119 days of reactor turned on and 211 days of reactor turned off are reported. Using a direct comparison between neutrino interaction rates of all cells, independent of any flux prediction, we find compatibility with the null oscillation hypothesis. The best fit point of the Reactor Antineutrino Anomaly is rejected at 99% C.L.