Search for a sub-eV sterile neutrino using Daya Bay's full dataset

TL;DR

This study used the full dataset from the Daya Bay Reactor Neutrino Experiment to search for sub-eV sterile neutrinos, setting new constraints on their mixing parameters and improving previous limits.

Contribution

It provides the most stringent constraints to date on light sterile neutrino mixing in the specified mass-squared difference range.

Findings

No significant sterile neutrino oscillation observed.

Exclusion of mixing angles .01 at 95% CL.

Set world-leading limits on sterile neutrino parameters.

Abstract

This Letter presents results of a search for the mixing of a sub-eV sterile neutrino with three active neutrinos based on the full data sample of the Daya Bay Reactor Neutrino Experiment, collected during 3158 days of detector operation, which contains $5.55 \times 10^{6}$ reactor \anue candidates identified as inverse beta-decay interactions followed by neutron-capture on gadolinium. The analysis benefits from a doubling of the statistics of our previous result and from improvements of several important systematic uncertainties. No significant oscillation due to mixing of a sub-eV sterile neutrino with active neutrinos was found. Exclusion limits are set by both Feldman-Cousins and CLs methods. Light sterile neutrino mixing with $\sin^2 2\theta_{14} \gtrsim 0.01$ can be excluded at 95\% confidence level in the region of $0.01$ eV$^2 \lesssim |\Delta m^{2}_{41}| \lesssim 0.1 $ eV$^2$. This result represents the world-leading constraints in the region of $2 \times 10^{-4}$ eV$^2 \lesssim |\Delta m^{2}_{41}| \lesssim 0.2 $ eV$^2$.