Searches for sterile neutrinos at the DANSS experiment

¹ Joint Institute for Nuclear Research, Joliot-Curie 6, Dubna, Moscow region 141980, Russia
² Alikhanov Institute for Theoretical and Experimental Physics NRC “Kurchatov Institute”, B. Cheremushkinskaya 25, Moscow 117218, Russia
³ Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninskiy Prospekt, Moscow 119991, Russia
⁴ Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region 141701, Russia

^a e-mail: mark.shirchenko@jinr.ru
^b e-mail: nataliya.skrobova@gmail.com

Published online: 12 December 2019

Abstract

DANSS is a highly segmented 1 m³ plastic scintillator detector. The DANSS detector is placed under an industrial 3.1 GW_th reactor of the Kalinin Nuclear Power Plant 350 km NW 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 background. DANSS detects almost 5000 ν_e per day at the closest position with the cosmic background less than 3%. The inverse beta decay process is used to detect ν_e. Sterile neutrinos are searched for assuming the 4ν model (3 active and 1 sterile ν). The exclusion area in the Δm₁₄²,sin²2θ₁₄ 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_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 sin²2θ₁₄ < 0.01 in the most sensitive region.