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Register a new userActive to sterile neutrino mixing limits from neutral-current interactions in MINOS
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Results are reported from a search for active to sterile neutrino oscillations in the MINOS long-baseline experiment, based on the observation of neutral-current neutrino interactions, from an exposure to the NuMI neutrino beam of $7.07times10^{20}$ protons on target. A total of 802 neutral-current event candidates is observed in the Far Detector, compared to an expected number of $754pm28rm{(stat.)}pm{37}rm{(syst.)}$ for oscillations among three active flavors. The fraction $f_s$ of disappearing umu that may transition to $ u_s$ is found to be less than 22% at the 90% C.L.
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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 $ u_{mu} rightarrow u_{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 $0.05~eV^2leq Delta m^2_{41}leq 0.5~eV^2$, the range of mass splittings that produce no significant oscillations over the Near Detector baseline.
We report the first detailed comparisons of the rates and spectra of neutral-current neutrino interactions at two widely separated locations. A depletion in the rate at the far site would indicate mixing between muon neutirnos and a sterile particle. No anomalous depletion in the reconstructed energy spectrum is observed. Assuming oscillations occur at a single mass-squared splitting, a fit to the neutral- and charged-current energy spectra limits the fraction of muon neutrino oscillating to a sterile neutrino to be below 0.68 at 90% confidence level. A less stringent limit due to a possible contribution to the measured neutral-current event rate at the far site from electron neutrino appearance at the current experimental limit is also presented.
This Letter reports results from the first long-baseline search for sterile antineutrinos mixing in an accelerator-based antineutrino-dominated beam. The rate of neutral-current interactions in the two NOvA detectors, at distances of 1 km and 810 km from the beam source, is analyzed using an exposure of $12.51times10^{20}$ protons-on-target from the NuMI beam at Fermilab running in antineutrino mode. A total of $121$ of neutral-current candidates are observed at the Far Detector, compared to a prediction of $122pm11$(stat.)$pm15$(syst.) assuming mixing between three active flavors. No evidence for $bar{ u}_{mu}rightarrowbar{ u}_{s}$ oscillation is observed. Interpreting this result within a 3+1 model, constraints are placed on the mixing angles ${theta}_{24} < 25^{circ}$ and ${theta}_{34} < 32^{circ}$ 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 produces no significant oscillations at the Near Detector. These are the first 3+1 confidence limits set using long-baseline accelerator antineutrinos.
Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the LSND and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on $sin^2 2theta_{mu e}$ are set over 6 orders of magnitude in the sterile mass-squared splitting $Delta m^2_{41}$. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for $Delta m^2_{41} < 0.8$ eV$^2$ at 95% CL$_s$.
Light sterile neutrinos have been introduced as an explanation for a number of oscillation signals at $Delta m^2 sim 1$ eV$^2$. Neutrino oscillations at relatively short baselines provide a probe of these possible new states. This paper describes an accelerator-based experiment using neutral current coherent neutrino-nucleus scattering to strictly search for active-to-sterile neutrino oscillations. This experiment could, thus, definitively establish the existence of sterile neutrinos and provide constraints on their mixing parameters. A cyclotron-based proton beam can be directed to multiple targets, producing a low energy pion and muon decay-at-rest neutrino source with variable distance to a single detector. Two types of detectors are considered: a germanium-based detector inspired by the CDMS design and a liquid argon detector inspired by the proposed CLEAR experiment.
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