Searches for sterile neutrinos at the DANSS experiment

DANSS is a highly segmented 1 m³ plastic scintillator detector. The DANSS detector is placed under an industrial 3.1 GWth reactor of the Kalinin Nuclear Power Plant 350 km north-west from Moscow. The distance to the core is varied on-line from 10.7 m to 12.7 m. The reactor building provides about 50 m water-equivalent shielding against the cosmic radiation background. DANSS detects almost 5000 ν-bar_e per day at the closest position with a cosmic background being less than 3%. The inverse beta decay process is used to detect ν-bar_e. Sterile neutrinos are searched for assuming the 4ν model (3 active and 1 sterile ν). The exclusion area in the Δm₁₄², sin²(2θ₁₄) plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor ν-bar_e spectrum nor the detector efficiency. Results are based on 966 thousand antineutrino events collected at three different distances from the reactor core. The excluded area covers a wide range of the sterile neutrino parameters down to sin²(2θ₁₄) < 0.01 in the most sensitive region. (authors)