Search for a Sub-eV Sterile Neutrino Using Daya Bay’s Full Dataset

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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 5.55×10⁶ reactor ν[over ¯]ₑ 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 sin²2θ₁₄≳0.01 can be excluded at 95% confidence level in the region of 0.01 eV²≲|Δm₄₁²|≲0.1 eV². This result represents the world-leading constraints in the region of 2×10⁻⁴ eV²≲|Δm₄₁²|≲0.2 eV².