| Summary: | The neutrino-nucleon interaction cross section at the TeV to EeV energy range has been calculated within the Standard Model using the parton distribution functions. Due to the limited energy from ground-based accelerators, the cross section in this energy range cannot be measured directly. The astrophysical neutrinos detected in the IceCube detector are a perfect candidate to perform this kind of measurement. IceCube is a 1 cubic kilometer size neutrino detector located at the South Pole. It is capable of detecting all-sky neutrinos of all favors from GeV to EeV energies. After the detector completion, the IceCube collaboration discovered and measured the flux of extraterrestrial neutrinos in the TeV - PeV energy range, along with the flux of neutrinos from the known atmospheric origin. This dissertation presents a novel analysis method and the result of the neutrino interaction total cross section measurement as a function of neutrino energy in the 6.3 TeV - 10 PeV energy range with neutrino-induced electromagnetic and hadronic showers (cascades) observed in five years of IceCube data. The final sample consists of 654 cascade events mainly induced by astrophysical electron and tau neutrinos with energies from 6.3 TeV to 10 PeV and all-sky directions. The events are assigned in four energy bins and two zenith bins ("down-going" from the southern hemisphere and "up-going" from the northern hemisphere). When assuming an all-sky isotropic astrophysical neutrino flux, the ratio of the down-going to the up-going events (which are absorbed by the Earth at high energies) is sensitive to the magnitude of the interaction cross section but insensitive to the large astrophysical neutrino flux uncertainties. The measured cross section is the combination of the Standard Model neutrino-nucleon deep inelastic scattering cross section and the Glashow Resonance cross section of electron antineutrino scattering offatomic electrons, which depends on the neutrino generation process type (pp or pγ) at the astrophysical source. The resulting cross section is consistent with the Standard Model expectation and with the previous IceCube results. With the next generation of IceCube (Gen2 upgrade), the measurement will potentially have the sensitivity to detect the Beyond Standard Model effects for neutrino energies above EeV if they exist.
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