Determining the wavelength dependancy of the optical properties of the glacial ice using in-situ light sources.

Neutrinos are unique cosmic messengers, their weak interactions and lack of electric charge means they can travel from cosmic distances, without absorption or deflection. IceCube is a neutrino observatory constructed at depths of 1450-2450 m below the surface at the South Pole. The main objective of IceCube is to detect astrophysical neutrinos to enable a better understanding of high-energy cosmic rays including their production mechanism and also their origins. IceCube observes neutrinos through detecting the light emitted by the products of neu- trino interactions. Characterisation of the optical properties of the glacial ice is necessary for the physical parameters of the neutrinos, such as their energies and directions, to be determined from the pattern and timing of the light detected. Embedded LEDs within the deployed modules enable the generation of in-situ light with five different wavelengths. This light can be detected by the detector array and used to determine the optical properties of the instrumented ice. The main focus of this thesis was to investigate and parameterise the wavelength de- pendence of the absorption and scattering coeffi cients of the ice. The values found for the parameters characterising this wavelength dependence were consistent with previous mea- surements although slightly different values were obtained. While the new parameters are considered to be more robust than past measurements due to improved knowledge of the light emitters, it is recommended that this study is revisited when the observed anisotropic light propagation has been further modelled. In addition to the main study into the wavelength dependence of the optical properties of the ice, investigations were also undertaken to characterise properties of the optical modules such as their orientation. Calibration tools developed and used in this thesis will be of use when the IceCube upgrade devices are deployed, allowing our knowledge and characterisation of the ice to be improved significantly

Multi-messenger searches via IceCube’s high-energy neutrinos and gravitational-wave detections of LIGO/Virgo

We summarize initial results for high-energy neutrino counterpart searches coinciding with gravitational-wave events in LIGO/Virgo\u27s GWTC-2 catalog using IceCube\u27s neutrino triggers. We did not find any statistically significant high-energy neutrino counterpart and derived upper limits on the time-integrated neutrino emission on Earth as well as the isotropic equivalent energy emitted in high-energy neutrinos for each event

Measuring the Neutrino Cross Section Using 8 years of Upgoing Muon Neutrinos Observed with IceCube

The IceCube Neutrino Observatory detects neutrinos at energies orders of magnitude higher than those available to current accelerators. Above 40 TeV, neutrinos traveling through the Earth will be absorbed as they interact via charged current interactions with nuclei, creating a deficit of Earth-crossing neutrinos detected at IceCube. The previous published results showed the cross section to be consistent with Standard Model predictions for 1 year of IceCube data. We present a new analysis that uses 8 years of IceCube data to fit the ν$_{μ}$ absorption in the Earth, with statistics an order of magnitude better than previous analyses, and with an improved treatment of systematic uncertainties. It will measure the cross section in three energy bins that span the range 1 TeV to 100 PeV. We will present Monte Carlo studies that demonstrate its sensitivity