Abstract
As atmospheric neutrinos propagate through the Earth, vacuum-like oscillations are modified by Standard-Model neutral- and charged-current interactions with electrons. Theories beyond the Standard Model introduce heavy, TeV-scale bosons that can produce nonstandard neutrino interactions. These additional interactions may modify the Standard Model matter effect producing a measurable deviation from the prediction for atmospheric neutrino oscillations. The result described in this paper constrains nonstandard interaction parameters, building upon a previous analysis of atmospheric muon-neutrino disappearance with three years of IceCube-DeepCore data. The best fit for the muon to tau flavor changing term is $\epsilon_{\mu \tau}=-0.0005$, with a 90\% C.L. allowed range of $-0.0067 <\epsilon_{\mu \tau}< 0.0081$. This result is more restrictive than recent limits from other experiments for $\epsilon_{\mu \tau}$. Furthermore, our result is complementary to a recent constraint on $\epsilon_{\mu \tau}$ using another publicly available IceCube high-energy event selection. Together, they constitute the world's best limits on nonstandard interactions in the $\mu-\tau$ sector.
Highlights
Neutrino flavor change has been observed and confirmed by a plethora of experiments involving solar, atmospheric, reactor, and accelerator-made neutrinos; see [1,2,3] and references therein
In the analysis presented here, we use the data set from [14] obtained with IceCube DeepCore with three years of runtime, which contains multi-GeV atmospheric neutrinos that traverse large fractions of the Earth before reaching the IceCube detector
For experiments like Super-Kamiokande and IceCube, the terms that correspond to νμ or ντ interactions will dominate. This is because the atmospheric neutrino flux in the GeV energy range is dominated by νμ, which primarily transform into ντ as they travel through the Earth [39,40]
Summary
Neutrino flavor change has been observed and confirmed by a plethora of experiments involving solar, atmospheric, reactor, and accelerator-made neutrinos; see [1,2,3] and references therein. The massive three-neutrino model has been very successful in explaining the neutrino data with two mass differences, known as the solar squared-mass difference (Δm221 ≈ 7.5 × 10−5 eV2) and the atmospheric squaredmass difference (jΔm223j ≈ 2.5 × 10−3 eV2) [1,2] This information, along with the fact that experiments pursuing direct neutrino mass measurements have yielded only upper limits [3], leads to the conclusion that neutrinos have masses that are at least 6 orders of magnitude smaller than those of the charged leptons. Independent studies of high-energy atmospheric neutrinos using public IceCube data [24] as well as studies with public SuperKamiokande data [25] have already been performed, obtaining strong constraints on NSI parameters.
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