Exploration of mass splitting and muon/tau mixing parameters for an eV-scale sterile neutrino with IceCube

Abstract

We present the first three-parameter fit to a 3+1 sterile neutrino model using 7.634 years of data from the IceCube Neutrino Observatory on ${\nu }_{\mu }+{\overline{\nu }}_{\mu }$ charged-current interactions in the energy range 500--9976 GeV. Our analysis is sensitive to the mass-squared splitting between the heaviest and lightest mass state ($\Delta m_{41}^2$), the mixing matrix element connecting muon flavor to the fourth mass state ($|U_{\mu 4}{|}^2$), and the element connecting tau flavor to the fourth mass state ($|U_{\tau 4}{|}^2$). Predicted propagation effects in matter enhance the signature through a resonance as atmospheric neutrinos from the Northern Hemisphere traverse the Earth to the IceCube detector at the South Pole. The remaining sterile neutrino matrix elements are left fixed, with $|U_{e4}{|}^2=0$ and ${\delta }_{14}=0$, as they have a negligible effect, and ${\delta }_{24}=\pi$ is set to give the most conservative limits. The result is consistent with the no-sterile neutrino hypothesis with a probability of 4.3%. Profiling the likelihood of each parameter yields the 90\% confidence levels: $2.4{\mathrm{eV}}^2<\Delta m_{41}^2<9.6{\mathrm{eV}}^2$ , $0.0081<|U_{\mu 4}{|}^2<0.10$ , and $|U_{\tau 4}{|}^2<0.035$, which narrows the allowed parameter-space for $|U_{\tau 4}{|}^2$. However, the primary result of this analysis is the first map of the 3+1 parameter space exploring the interdependence of $\Delta m_{41}^2$, $|U_{\mu 4}{|}^2$, and $|U_{\tau 4}{|}^2$.

14 pages, 8 figures. Published in PLB

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