Sterile Neutrino Search at the NEOS Experiment

Y. J. Ko, B. R. Kim, J. Y. Kim, B. Y. Han, C. H. Jang, E. J. Jeon, K. K. Joo, H. J. Kim, H. S. Kim, Y. D. Kim, Jaison Lee, J. Y. Lee (+8 others)
2017 Physical Review Letters  
An experiment to search for light sterile neutrinos was conducted at a reactor with a thermal power of 2.8 GW located at the Hanbit nuclear power complex. The search was done with a detector consisting of a ton of Gd-loaded liquid scintillator in a tendon gallery approximately 24 m from the reactor core. The measured antineutrino event rate is 1976 per day with a signal to background ratio of about 22. The shape of the antineutrino energy spectrum obtained from eight-month data-taking period is
more » ... ta-taking period is compared with a hypothesis of oscillations due to active-sterile antineutrino mixing. It is found to be consistent with no oscillation. An excess around 5 MeV prompt energy range is observed as seen in existing longer baseline experiments. The parameter space of $\sin^{2}2\theta_{14}$ down below 0.1 for $\Delta m^{2}_{41}$ ranging from 0.2 eV$^{2}$ to 2.3 eV$^{2}$ and the optimum point for the previously reported reactor antineutrino anomaly are excluded with a confidence level higher than 90%.
doi:10.1103/physrevlett.118.121802 pmid:28388195 fatcat:cf5foqrkabcpnayq46es4nyqgu