Searches for Sterile Neutrinos with the IceCube Detector

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320 GeV to 20 TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous ${\nu }_{\mu }$ or ${\overline{\nu }}_{\mu }$ disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the $3+1$ model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to ${\sin }^{2}2{\theta }_{24}\le 0.02$ at $\mathrm{\Delta }{m}^2\sim 0.3{\mathrm{eV}}^2$ at the 90% confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99% confidence level for the global best-fit value of $|U_{e4}{|}^2$.

Figure 1

Top and center: change in the spectrum due to propagation effects for muon neutrinos and antineutrinos at the $3+1$ global best-fit point. Bottom: The predicted event rate reduction (in percent) vs reconstructed muon energy and zenith angle for this model.

Figure 2

Reconstructed energy distribution in data and Monte Carlos events for the no-sterile-neutrino hypothesis in the analysis.

Figure 3

The statistical-only pulls ($\text{shape}+\text{rate}$ analysis) per reconstructed energy and zenith angle bin at the best nuisance parameter fit point for the no-sterile-neutrino hypothesis. The shown empty bins are those that were evaluated in the analysis but had no data events remaining following cuts.

Figure 4

Results from IceCube sterile neutrino searches (regions to the right of the contours are excluded). The dot-dashed blue line shows the result of the original analysis based on shape alone, while the solid red line shows the final result with a normalization prior included to prevent degeneracies between the no-sterile-neutrino hypothesis and sterile neutrinos with masses outside the range of sensitivity. The dashed black line is the exclusion range derived from an independent analysis of data from the 59-string IceCube configuration.

Figure 5

Results from the IceCube search. (Top) The 90% (orange solid line) C.L. contour is shown with bands containing 68% (green) and 95% (yellow) of the 90% contours in simulated pseudoexperiments, respectively. (Bottom) The 99% (red solid line) C.L. contour is shown with bands containing 68% (green) and 95% (yellow) of the 99% contours in simulated pseudoexperiments, respectively. The contours and bands are overlaid on 90% C.L. exclusions from previous experiments [7, 8, 9, 10], and the 99% C.L. allowed region from global fits to appearance experiments including MiniBooNE and LSND, assuming $|U_{e4}{|}^2=0.023$ [12] and $|U_{e4}{|}^2=0.027$ [13], respectively.