Statistical data analysis in the DANSS experiment

DANSS is a one cubic meter highly segmented solid scintillator detector. It is placed under a 3.1 GW industrial reactor at the Kalinin NPP (Russia) on a movable platform. The distance from the reactor core center is varied from 10.7 m to 12.7 m on-line. The inverse beta decay (IBD) process is used to detect antineutrinos. DANSS detects about 5000 IBD events per day.Sterile neutrinos are searched for assuming a 4 neutrino model (3 active and 1 sterile neutrino). The exclusion area in the sterile neutrino parameter 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 v ˜ e spectrum, as well as on the detector efficiency. The excluded area covers a wide range of the sterile neutrino parameters up to sin 2 2 θ 14 < 0.01 in the most sensitive region. The Reactor Antineutrino Anomaly optimum point is excluded with a confidence level higher than 5 σ . A Gaussian CL s method was used to obtain exclusion areas. CL s method includes a point from sin 2 2 θ , Δ m 2 plane into exclusion area only if the experiment sensitivity to such point is good. Details of this approach are presented.