Search for Sub-eV Sterile Neutrino at RENO

TL;DR

The RENO experiment searched for light sterile neutrino oscillations using reactor antineutrino disappearance over 2200 days, finding no evidence but setting the most stringent limits on sterile neutrino mixing at low mass-squared differences.

Contribution

This study provides new constraints on light sterile neutrino parameters using reactor antineutrino data, improving limits at low mass-squared differences.

Findings

Spectral comparison shows no deviation from three-flavor oscillation model.

Set the most stringent limits on sterile neutrino mixing for | m|  0.002 eV.

Excluded certain parameter regions for light sterile neutrinos.

Abstract

We report a search result for a light sterile neutrino oscillation with roughly 2200 live days of data in the RENO experiment. The search is performed by electron antineutrino ($\overline{\nu}_e$) disappearance taking place between six 2.8 GW$_{\text{th}}$ reactors and two identical detectors located at 294 m (near) and 1383 m (far) from the center of reactor array. A spectral comparison between near and far detectors can explore reactor $\overline{\nu}_e$ oscillations to a light sterile neutrino. An observed spectral difference is found to be consistent with that of the three-flavor oscillation model. This yields limits on $\sin^{2} 2\theta_{14}$ in the $10^{-4} \lesssim |\Delta m_{41}^2| \lesssim 0.5$ eV$^2$ region, free from reactor $\overline{\nu}_e$ flux and spectrum uncertainties. The RENO result provides the most stringent limits on sterile neutrino mixing at $|\Delta m^2_{41}| \lesssim 0.002$ eV$^2$ using the $\overline{\nu}_e$ disappearance channel.