Sterile Neutrino Searches at the IceCube Neutrino Observatory

The IceCube Neutrino Observatory is capable of performing a unique search for sterile neutrinos through the exploitation of a matter enhanced resonant neutrino oscillation phenomena. As atmospheric muon neutrinos pass the dense material within the Earth, neutral current elastic forward scattering is predicted to induce a transition into a sterile state. This thesis presents two 3+1 sterile neutrino analyses by searching for spectral differences in the reconstructed energy and zenith direction of muon neutrino events, indicative of a transition into a sterile state. The first search probes the parameter space $\mathrm{\Delta }$m${}_{41}^2$ and sin${}^2$(2${\theta }_{24}$) with relevant sensitivity to the global best fit region for a 3+1 sterile neutrino hypothesis. The second search performs a scan through sin${}^2$(2${\theta }_{24}$) and sin${}^2$(2${\theta }_{34}$) in the oscillation averaged out region of high-$\mathrm{\Delta }$m${}_{41}^2$ ($\mathrm{\Delta }$m${}_{41}^2$ $\gtrsim$ 10eV${}^2$). The analyses are performed using an improved event selection, which was found to extract 305,891 well reconstructed muon neutrino events with a sample purity above 99.9%, from eight years of IceCube data. Novel simulation techniques, along with updated calibration, and a re-assessment of the systematic uncertainties are also discussed. The first analysis finds a best fit sterile hypothesis point at $\mathrm{\Delta }$m${}_{41}^2$ = 4.47eV${}^2$ and sin${}^2$(${\theta }_{24})$ =0.10, consistent with the no-sterile hypothesis at the 8% confidence level. The second analysis finds a best fit sterile hypothesis at sin${}^2$(${\theta }_{34})$ = 0.40, sin${}^2$(${\theta }_{24})$ = 0.006, consistent with the null hypothesis at the 19% confidence level. % and provides a significant improvement in the worlds measurements using muon neutrino disappearance.