We report results from the first search for sterile neutrinos mixing with active neutrinos through a reduction in the rate of neutral-current interactions over a baseline of 810\,km between the NOvA detectors. Analyzing a 14-kton detector equivalent exposure of 6.05$\times$10$^{ 20}$ protons-on-target in the NuMI beam at Fermilab, we observe 95 neutral-current candidates at the Far Detector compared with $83.5 \pm 9.7 \mbox{ (stat.)} \pm 9.4 \mbox{ (syst.)}$ events predicted assuming mixing only occurs between active neutrino species. No evidence for $\nu_{ \mu} \rightarrow \nu_{ s}$ transitions is found. Interpreting these results within a 3+1 model, we place constraints on the mixing angles $\theta_{ 24}<20.8^{ \circ}$ and $\theta_{ 34}<31.2^{ \circ}$ at the 90% C.L. for $0.05~eV^2\leq \Delta m^2_{ 41}\leq 0.5~eV^2$, the range of mass splittings that produce no significant oscillations over the Near Detector baseline.
Categories: hep-ex