We present a search for an unstable sterile neutrino by looking for a resonant signal in eight years of atmospheric ${\nu }_{\mu }$ 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 $\mathrm{\Delta }{m}_{41}^2=6.7_{-2.5}^{+3.9}{\mathrm{eV}}^2$, ${\sin }^{2}2{\theta }_{24}=0.33_{-0.17}^{+0.20}$, and $g^2=2.5\pi \pm 1.5\pi$, 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.

• Received 6 April 2022
• Revised 17 August 2022
• Accepted 23 August 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.151801

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Published by the American Physical Society