Testing the neutrino mass ordering with IceCube DeepCore

Dissertation, RWTH Aachen University, 2018; Aachen 1 Online-Ressource (xi, 177 Seiten) : Illustrationen (2018). = Dissertation, RWTH Aachen University, 2018
The Neutrino Mass Ordering (NMO) describes the energetic ordering of the three neutrino masses m1, m2 and m3. Today, the ordering is constrained up to the question of m3 being the heaviest or the lightest of all neutrino masses, which is commonly called Normal (NO) and Inverted Ordering (IO), respectively. One way to determine the NMO is to measure matter effects in the oscillation pattern of atmospheric neutrinos. In this work, an analysis of three years of DeepCore data is presented to test the Neutrino Mass Ordering. To do this, a new event reconstruction was developed in this work, which provides excellent resolutions in neutrino energy and zenith-angle at the lowest energies. The Neutrino Mass Ordering is fit in a maximum-likelihood method, which includes systematic uncertainties in the atmospheric fluxes, the oscillation parameters, the detector response and the neutrino-nucleon interactions as nuisance parameters in the likelihood fit. In experimental data, a preference for Normal over Inverted Ordering is found with p-values of 71.1% for NO (CLs = 83.0%) and 15.2% for IO (CLs = 53.3%). This is inline with recent observations of the NOvA, T2K and Super-Kamiokande experiments. Moreover, the fit prefers matter effects (MA) over vacuum oscillations (VA) in case of both ordering hypotheses. Besides the experimental result, this work provides a proof-of-concept for an analysis of the Neutrino Mass Ordering with a future low-energy extension of IceCube, such as PINGU. It tests the full analysis-chain, including the statistical interpretation of the experimental result and the understanding of systematic uncertainties. Thus, it provides a benchmark analysis for these more sensitive future measurements.
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