Testing nonstandard neutrino interaction parameters with IceCube-DeepCore

Abstract

Currently, the clearest evidence for physics beyond the Standard Model is provided by observations that indicate non-zero neutrino masses. Numerous theories on how these masses are generated give rise to additional non-standard interactions (NSI) of neutrinos with quarks and charged leptons. Atmospheric neutrinos provide a sensitive probe for the neutrino flavor transitions resulting from the type of NSI investigated in this work. These comprise neutral current forward scattering of neutrinos of all flavors on first generation charged fermions in Earth matter. In order to maximize model independence, the NSI are parametrized using five effective coupling strengths. In the IceCube-DeepCore detector, atmospheric neutrinos are detected indirectly via Cherenkov photons produced within the Antarctic glacier. The range of angles under which neutrinos enter the detector translates into propagation baselines of O(1 − 10000 )km. The data sample used in the presented analysis includes 9.3 years of DeepCore data, covering a neutrino energy range of 5 to 100 GeV. Accuracy and performance of event property reconstruction from observed photons are a crucial factor for the analysis outcome. Therefore, this work includes a thorough study of the potential and shortcomings of likelihood based DeepCore event reconstruction algorithms. The presented analysis relies on comparing binned observed event counts to simulation that is generated at different hypotheses. These include the individually considered NSI parameters as well as 17 nuisance parameters. In order to find the hypothesis that best describes the observation, the optimum of a test statistic is determined using a customized minimization strategy. The final analysis setup yields sensitivities to four effective NSI couplings that are competitive compared with existing results.