Abstrakt
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 x 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 +/- 9.7(stat) +/- 9.4(syst) events predicted assuming mixing only occurs between active neutrino species.
No evidence for upsilon(mu) -> upsilon(mu) transitions is found. Interpreting these results within a 3 + 1 model, we place constraints on the mixing angles theta(24) < 20.8 degrees and theta(34) < 31.2 degrees at the 90% C.L. for 0.05 eV(2) <= Delta m(41)(2) <= 0.5 eV(2), the range of mass splittings that produce no significant oscillations over the Near Detector baseline.