Search for Light Unstable Sterile Neutrinos in IceCube

Longstanding anomalies observed in short-baseline neutrino oscillation experiments have motivated an eV-scale sterile neutrino. Because of matter effects within the Earth, the existence of this particle would cause a deficit in the atmospheric and astrophysical muon neutrino flux at TeV energies for neutrinos crossing the Earth. We present the results of a search for an unstable sterile neutrino in IceCube. In this model, which is motivated by decreased tension in the global fits, the heaviest neutrino mass state may decay. The unstable sterile neutrino model is preferred to the three-neutrino model and 3+1 models with p-values of 2.5% and 0.81%, respectively. The best-fit parameters for the unstable sterile neutrino model are , , and , where g is the decay-mediating coupling. We find no evidence for the unstable sterile neutrino model.