Search for Unstable Sterile Neutrinos with the IceCube Neutrino Observatory

We present a search for an unstable sterile neutrino by looking for a resonant signal in eight years of atmospheric ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ data collected from 2011 to 2019 at the IceCube Neutrino Observatory. Both the (stable) three-neutrino and the $3+1$ sterile neutrino models are disfavored relative to the unstable sterile neutrino model, though with $p$ values of 2.8% and 0.81%, respectively, we do not observe evidence for $3+1$ neutrinos with neutrino decay. The best-fit parameters for the sterile neutrino with decay model from this study are $\mathrm{\ensuremath{\Delta}}{m}_{41}^{2}=6.{7}_{\ensuremath{-}2.5}^{+3.9}\text{ }\text{ }{\mathrm{eV}}^{2}$, ${\mathrm{sin}}^{2}2{\ensuremath{\theta}}_{24}=0.3{3}_{\ensuremath{-}0.17}^{+0.20}$, and ${g}^{2}=2.5\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}1.5\ensuremath{\pi}$, where $g$ is the decay-mediating coupling. The preferred regions of the $3+1+\text{decay}$ model from short-baseline oscillation searches are excluded at 90% C.L.

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