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Register a new userSearch for active neutrino disappearance using neutral-current interactions in the MINOS long-baseline experiment
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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.
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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.
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.
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.
The MINOS/MINOS+ experiment has recently reported stringent limits on $ u_mu$ disappearance that appear to rule out the 3+1 sterile neutrino model. However, in this paper we wish to point out problems associated with the MINOS/MINOS+ analysis. In particular, we find that MINOS/MINOS+ has either underestimated their systematic errors and/or has obtained evidence for physics beyond the 3-neutrino paradigm. Either case would invalidate the limits on $ u_mu$ disappearance.
We searched for a sidereal modulation in the rate of neutrinos produced by the NuMI beam and observed by the MINOS far detector. The detection of such harmonic signals could be a signature of neutrino-antineutrino mixing due to Lorentz and CPT violation as described by the Standard Model Extension framework. We found no evidence for these sidereal signals and we placed limits on the coefficients in this theory describing the effect. This is the first report of limits on these neutrino-antineutrino mixing coefficients.
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