Active to Sterile Neutrino Mixing Limits from Neutral-Current Interactions in MINOS

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 $7.07\times {10}^{20}$ protons on target. A total of 802 neutral-current event candidates is observed in the Far Detector, compared to an expected number of $754\pm 28(\mathrm{stat})\pm 37(\mathrm{syst})$ for oscillations among three active flavors. The fraction $f_s$ of disappearing ${\nu }_{\mu }$ that may transition to ${\nu }_s$ is found to be less than 22% at the 90% C.L.

Figure 1

Reconstructed energy spectrum of NC-selected events in the ND (solid points) compared to the Monte Carlo prediction (open histogram) shown with $1\sigma$ systematic errors (shaded band). Also displayed is the simulation of the background from misidentified CC events (hatched histogram).

Figure 2

Reconstructed energy spectrum of NC-selected events in the FD (points with statistical errors) compared with predictions for standard three-flavor mixing with and without ${\nu }_e$ appearance at the MINOS 90% C.L. limit [20] (dashed and solid lines, respectively).