University of Wisconsin-Madison

Research Highlights: Neutrino Physics

The DeepCore subdetector allows IceCube to extend the measurement of the neutrino flux from 100 TeV down to below 10 GeV. At these energies, we observe atmospheric neutrino oscillations and perform searches for sterile neutrinos. We have measured the atmospheric oscillation parameters with a precision compatible with and comparable to those of the dedicated oscillation experiments, such as MINOS, T2K, or Super-Kamiokande.

Oscillation parameters measured with three years of DeepCore data (2012-2014). The 90% confidence contours are shown in comparison with those of the most sensitive experiments. At the top and on the right side of the figure, the log-likelihood profiles for individual oscillation parameters are given. Normal mass hierarchy is assumed.
Oscillation parameters measured with three years of DeepCore data (2012-2014). The 90% confidence contours are shown in comparison with those of the most sensitive experiments. At the top and on the right side of the figure, the log-likelihood profiles for individual oscillation parameters are given. Normal mass hierarchy is assumed.

IceCube has also conducted two searches for light sterile neutrinos, one using high-energy atmospheric neutrinos detected in IceCube and another using low-energy neutrinos detected in DeepCore. None of the searches found evidence for anomalous muon neutrino disappearance and the limits exclude at 99% confidence level the allowed region from appearance experiments such as LSND and MiniBooNE. The search with low-energy neutrinos provided exclusion limits for the sterile neutrino oscillation parameters, with a new world-best limit on the |Uτ4|2 mixing matrix element.

Results from the IceCube search for light sterile neutrinos using high-energy atmospheric neutrinos. The 99% (red solid line) CL contour is shown with bands containing 68% (green) and 95% (yellow) of the 99% contours in simulated pseudo-experiments, respectively. The contours and bands are overlaid on 90% CL exclusions from previous experiments and the MiniBooNE/LSND 99% CL allowed region.
Results from the IceCube search for light sterile neutrinos using high-energy atmospheric neutrinos. The 99% (red solid line) CL contour is shown with bands containing 68% (green) and 95% (yellow) of the 99% contours in simulated pseudo-experiments, respectively. The contours and bands are overlaid on 90% CL exclusions from previous experiments and the MiniBooNE/LSND 99% CL allowed region.
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Take a closer look at the highest energy neutrinos.