We present the first statistically significant detection of neutrino oscillations in the high-energy regime ($>20\mathrm{GeV}$) from an analysis of IceCube Neutrino Observatory data collected in 2010 and 2011. This measurement is made possible by the low-energy threshold of the DeepCore detector ($\sim 20\mathrm{GeV}$) and benefits from the use of the IceCube detector as a veto against cosmic-ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20–100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV–10 TeV) was extracted from IceCube data to constrain systematic uncertainties. The disappearance of low-energy upward-going muon neutrinos was observed, and the nonoscillation hypothesis is rejected with more than $5\sigma$ significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters $|\Delta m_{32}^2|=({2.3}_{-0.5}^{+0.6})\times {10}^{-3}{\mathrm{eV}}^2$ and ${sin}^2(2{\theta }_{23})>0.93$, and maximum mixing is favored.

• Received 16 May 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.081801