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

Non-standard neutrino interactions in IceCube

Non-standard neutrino interactions (NSI) may arise in various types of new physics. Their existence would change the potential that atmospheric neutrinos encounter when traversing Earth matter and hence alter their oscillation behavior. This imprint on coherent neutrino forward scattering can be probed using high-statistics neutrino experiments such as IceCube and its low-energy extension, DeepCore. Both provide extensive data samples that include all neutrino flavors, with oscillation baselines between tens of kilometers and the diameter of the Earth. DeepCore event energies reach from a few GeV up to the order of 100 GeV - which marks the lower threshold for higher energy IceCube atmospheric samples, ranging up to 10 TeV. In DeepCore data, the large sample size and energy range allow us to consider not only flavor-violating and flavor-nonuniversal NSI in the μ−τ sector, but also those involving electron flavor. The effective parameterization used in our analyses is independent of the underlying model and the new physics mass scale. In this way, competitive limits on several NSI parameters have been set in the past. The 8 years of data available now result in significantly improved sensitivities. This improvement stems not only from the increase in statistics but also from substantial improvement in the treatment of systematic uncertainties, background rejection and event reconstruction