Limiting the Parameter Space for Unstable eV-Scale Neutrinos Using IceCube Data

This Letter extends a recent IceCube sterile neutrino search to include unstable sterile neutrinos within the context of a model termed 3+1+Decay, which expands upon the 3+1 model by introducing sterile neutrino decay to invisible particles with coupling constant 𝑔². The model is attractive since it reduces tension between oscillation experiments within the global fits and with constraints that come from cosmological observables. The analysis uses 10.7 years of up-going muon neutrino data with energy 500 GeV to 100 TeV and with improved reconstruction and modeling of systematics. The best-fit point is found to be 𝑔² =0, sin²⁡(2⁢𝜃₂₄) =0.16, and Δ⁢𝑚2/41 =3.5 eV², in agreement with the recent 3+1 sterile neutrino search. Values of 𝑔² ≥𝜋 are excluded at 95% confidence level. This result substantially limits decay parameter space indicated by recent global fits, disfavoring the decay scenario.