Searching for eV-scale sterile neutrinos with eight years of atmospheric neutrinos at the IceCube Neutrino Telescope

Abstract

We report in detail on searches for eV-scale sterile neutrinos, in the context of a 3 þ 1 model, using eight years of data from the IceCube Neutrino Telescope. By analyzing the reconstructed energies and zenith angles of 305,735 atmospheric ν μ andν μ events we construct confidence intervals in two analysis spaces: sin 2 ð2θ 24 Þ vs Δm 2 41 under the conservative assumption θ 34 ¼ 0; and sin 2 ð2θ 24 Þ vs sin 2 ð2θ 34 Þ given sufficiently large Δm 2 41 that fast oscillation features are unresolvable. Detailed discussions of the event selection, systematic uncertainties, and fitting procedures are presented. No strong evidence for sterile neutrinos is found, and the best-fit likelihood is consistent with the no sterile neutrino hypothesis with a p value of 8% in the first analysis space and 19% in the second.

eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory

“…Details can be found in Refs. [65,126]. Furthermore, a similar best-fit point is obtained when fitting any one year of data independently, suggesting a small effect of physical or systematic rather than statistical origin.…”

“…At this point, the largest nuisance parameter pull was observed in the cosmic-ray spectral index, which shifted the cosmic-ray spectrum by 0.068 (2.3σ); the other nuisance parameter best-fit values are within one sigma of their respective central values and can be found in the accompanying Ref. [65]. Figure 3 shows the signal shape at the best-fit point, given the best-fit nuisance parameters, as well as the pull between data and no sterile neutrino hypothesis, evaluated at those same nuisance parameters.…”

“…A companion paper, Ref. [65], contains a more detailed exposition of the technical aspects of the analysis, as well as alternate interpretations of the data in a wider space of sterile neutrino parameters.…”

“…A highlevel event selection is applied, leveraging morphology, measures of track reconstruction quality, and the expected transmission of signal events through the zenith-dependent overburden, explained in detail in Ref. [65] and based on Ref. [77].…”

“…The ν μ and cosmic-ray muon tracks are separated into sub-events using an event splitter, and each subevent is treated independently in the event selection. After splitting and event selection, the sample is predicted to be > 99.9% pure in ν μ =ν μ induced events [65].…”