Testing nonstandard neutrino interaction parameters with IceCube-DeepCore
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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.