title: Sterile Neutrino Search at the NEOS Experiment.
abstract: An experiment to search for light sterile neutrinos is conducted at a reactor with a thermal power of 2.8 GW located at the Hanbit nuclear power complex. The search is 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 the eight-month data-taking period is compared with a hypothesis of oscillations due to active-sterile antineutrino mixing. No strong evidence of 3+1 neutrino oscillation is found. An excess around the 5 MeV prompt energy range is observed as seen in existing longer-baseline experiments. The mixing parameter sin^{2}2θ_{14} is limited up to less than 0.1 for Δm_{41}^{2} ranging from 0.2 to 2.3 eV^{2} with a 90% confidence level.
authors.affiliation: Department of Physics, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Ko
authors.affiliation: Department of Physics, Chonnam National University, Gwangju 61186, Korea.
authors.forename: B R
authors.initials: BR
authors.lastname: Kim
authors.affiliation: Department of Physics and Astronomy, Sejong University, Seoul 05006, Korea.
authors.forename: J Y
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea.
authors.forename: B Y
authors.initials: BY
authors.lastname: Han
authors.affiliation: Department of Physics, Chung-Ang University, Seoul 06974, Korea.
authors.forename: C H
authors.initials: CH
authors.lastname: Jang
authors.affiliation: Center for Underground Physics, Institute for Basic Science (IBS), Daejeon 34047, Korea.
authors.forename: E J
authors.initials: EJ
authors.lastname: Jeon
authors.affiliation: Department of Physics, Chonnam National University, Gwangju 61186, Korea.
authors.forename: K K
authors.initials: KK
authors.lastname: Joo
authors.affiliation: Department of Physics, Kyungpook National University, Daegu 41566, Korea.
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Physics and Astronomy, Sejong University, Seoul 05006, Korea.
authors.forename: H S
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Physics and Astronomy, Sejong University, Seoul 05006, Korea.|Center for Underground Physics, Institute for Basic Science (IBS), Daejeon 34047, Korea.|University of Science and Technology, Daejeon 34113, Korea.
authors.forename: Y D
authors.initials: YD
authors.lastname: Kim
authors.affiliation: Center for Underground Physics, Institute for Basic Science (IBS), Daejeon 34047, Korea.
authors.forename: Jaison
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Physics, Kyungpook National University, Daegu 41566, Korea.
authors.forename: J Y
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Center for Underground Physics, Institute for Basic Science (IBS), Daejeon 34047, Korea.
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
authors.affiliation: Center for Underground Physics, Institute for Basic Science (IBS), Daejeon 34047, Korea.
authors.forename: Y M
authors.initials: YM
authors.lastname: Oh
authors.affiliation: Center for Underground Physics, Institute for Basic Science (IBS), Daejeon 34047, Korea.|University of Science and Technology, Daejeon 34113, Korea.
authors.forename: H K
authors.initials: HK
authors.lastname: Park
authors.affiliation: Korea Research Institute of Standards and Science, Daejeon 34113, Korea.
authors.forename: H S
authors.initials: HS
authors.lastname: Park
authors.affiliation: Center for Underground Physics, Institute for Basic Science (IBS), Daejeon 34047, Korea.
authors.forename: K S
authors.initials: KS
authors.lastname: Park
authors.affiliation: Department of Physics and Astronomy, Sejong University, Seoul 05006, Korea.
authors.forename: K M
authors.initials: KM
authors.lastname: Seo
authors.affiliation: Department of Physics, Chung-Ang University, Seoul 06974, Korea.
authors.forename: Kim
authors.initials: K
authors.lastname: Siyeon
authors.affiliation: Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea.
authors.forename: G M
authors.initials: GM
authors.lastname: Sun