Abstract
We present a search for a light sterile neutrino using three years of atmospheric neutrino data from the DeepCore detector in the energy range of approximately $10-60~$GeV. DeepCore is the low-energy sub-array of the IceCube Neutrino Observatory. The standard three-neutrino paradigm can be probed by adding an additional light ($\Delta m_{41}^2 \sim 1 \mathrm{\ eV^2}$) sterile neutrino. Sterile neutrinos do not interact through the standard weak interaction, and therefore cannot be directly detected. However, their mixing with the three active neutrino states leaves an imprint on the standard atmospheric neutrino oscillations for energies below 100 GeV. A search for such mixing via muon neutrino disappearance is presented here. The data are found to be consistent with the standard three neutrino hypothesis. Therefore we derive limits on the mixing matrix elements at the level of $|U_{\mu4}|^2 < 0.11 $ and $|U_{\tau4}|^2 < 0.15 $ (90% C.L.) for the sterile neutrino mass splitting $\Delta m_{41}^2 = 1.0$ eV$^2$.
Highlights
Neutrino oscillation is a phenomenon in which a neutrino can be detected as a different weak eigenstate than initially produced after traveling some distance to its detection point
The neutrino flavor eigenstates of the weak interaction do not coincide with the mass states, which describe the propagation of neutrinos through space [31]
The addition of a sterile neutrino state modifies the neutrino oscillations in two ways that are relevant for this analysis
Summary
Neutrino oscillation is a phenomenon in which a neutrino can be detected as a different weak eigenstate than initially produced after traveling some distance to its detection point. The effect is confirmed by a variety of measurements of neutrinos produced in the Sun [1,2,3,4,5,6], in the atmosphere [7,8,9], at nuclear reactors [10,11,12,13] and at particle accelerators [14,15,16,17] The data from these experiments are often interpreted within the framework of three weakly interacting neutrino flavors, where each is a superposition of three neutrino mass states. The measurement of the Z0 boson decay width at the Large Electron-Positron (LEP) collider limits the number of the weakly interacting light neutrino states to three [22] This implies that new neutrino species must be “sterile” and not take part in the standard weak interaction.
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