The Search For High Energy Tau Neutrinos Using The Icecube Neutrino Observatory

High energy neutrinos provide a new frontier of astrophysical and particle physics research. Astrophysical neutrinos are produced at the same sources as hadronic cosmic rays throughout the universe in many different accelerators. These neutrinos propagate a very long distance to reach the Earth during which they experience oscillations between the flavors, including tau neutrinos which are not produced at the source. Astrophysical tau neutrinos are a clear sign of neutrino oscillations, which can shed light on beyond standard model physics at energy scales and distance scales not yet explored. The signature of the BSM physics can be seen in the flavor ratio of astrophysical neutrinos. However, astrophysical tau neutrinos have not yet been observed by IceCube, this dissertation is on my work to observe astrophysical tau neutrinos. The work presented here is about an improved analysis to observe astrophysical tau neutrinos using novel observation techniques, a critical key in measuring the astrophysical neutrino flavor ratio. Neutrino oscillations, interactions, and observe techniques will be explored along with the methods to improve a previous analysis of IceCube data to observe neutrinos. The main signature used to observe tau neutrinos is a double pulse waveform, where a single DOM observes the Cherenkov light signals associated with both the tau neutrino interaction and the decay of the tau that it produced. This analysis focuses on observing O (100 TeV) tau neutrinos via double pulse waveforms in 8.5 years of data. The analysis observed two neutrino candidates and one probable muon background event which resulting in setting upper limits of tau neutrino flux at 1.1×10^(−18) ×E^(−2.19), 2.5×10^(−18) ×E^(−2.5), and 6.0^(−18) ×E^(−2.9)GeV^(−1)cm^(−2)s^(−1)sr^(−1).