| Popis: |
MINOS+, a three year extension of the successful MINOS experiment, is a long-baseline neutrino experiment consisting of a beam originating at the NuMI beam facility, which is sampled 1 km downstream from in the 1 kt Near Detector at Fermilab, and again at 735 km downstream in the 5.4 kt Far Detector in the Soudan Underground Laboratory. Comparison of measurements taken at the Near and Far Detectors allows MINOS+ to probe with great precision the atmospheric domain of neutrino oscillations. Through observation of both neutral-current and charged-current weak interactions, MINOS+ is sensitive to both the muon neutrino survival and muon neutrino disappearance along its long baseline, which not only permits the high-precision measurement of $\Delta m^2_{32}$ and $\theta_{23}$ in the standard three-flavor neutrino oscillations model but also allows for searches for anomalous oscillation behaviors. Here we show that observation of the anomalous disappearance of muon neutrinos can be interpreted in the context of oscillations in a phenomenological model containing three active neutrino flavor eigenstates and one sterile neutrino eigenstate. Using this type of model, we demonstrate that the MINOS+ experiment, in combination with data collected during the MINOS era, achieves world-leading sensitivity to the sterile neutrino eigenstate over seven orders of magnitude in the mass-splitting $\Delta m^2_{41}$. |
