Sterile Neutrino Search in the Neutrino-4 Experiment at the SM-3 Reactor
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Abstract
First results on the energy spectrum and flux of reactor antineutrinos as a function of the distance L from the reactor core, measured in the Neutrino-4 experiment for 6 < L < 12 m, are presented. The flux L‑dependence fits to the 1/L2 form with a statistical significance of ~10% corresponding to 1.64σ, so that the measured spectrum deviates from the 1/L2 law at a confidence level ~90%. The measured energy spectrum deviates from the predicted one at a similar confidence level ~90%. That both deviations are best described with oscillation parameters in the same regions of \(\Delta m_{{14}}^{2} \approx 0.7{\text{-}}0.8\) eV2and \({{\sin }^{2}}2{{\Theta }_{{14}}} \approx 0.10{\text{-}}0.15\) boosts the overall confidence level to ~95% (2σ). These results suggest that antineutrinos oscillate to a sterile state, but still fall short of reliably establishing the oscillation phenomenon. At present, the possibility of mimicking the oscillation effect by systematic errors cannot be completely excluded.
Notes
ACKNOWLEDGMENTS
This work was supported by the Russian Foundation for Basic Research under Agreement no. 14-22-03055-ofi_m. The delivery of liquid scintillator from the laboratory headed by Professor Jun Cao (Institute of High Energy Physics, Beijing, China) was an important contribution to this work.
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