Search for an Unstable Sterile Neutrino in IceCube
Longstanding anomalies in neutrino oscillation experiments suggest the existence of a fourth, hypothetical neutrino: the sterile neutrino. Global fits to an eV-scale 3+1 sterile neutrino model find a strong preference for such a model over the Standard Model. However, the fit results suffer from inconsistencies between datasets. This motivates more complicated models for new physics. Here, we consider an unstable sterile neutrino model, where the heaviest neutrino mass state may decay, in the case of the IceCube experiment. IceCube is a gigaton ice-Cherenkov neutrino detector located at the South Pole. Searches for eV-scale sterile neutrinos in IceCube make use of a matter resonance that occurs for neutrinos crossing the core of the Earth. In this search, we find a preference for the unstable sterile neutrino model over the three-neutrino model with a p-value of 2.5%.
Marjon Moulai is the Balzan Fellow at the Wisconsin IceCube Particle Astrophysics Center at the University of Wisconsin, Madison. She received her PhD in 2021 from the Massachusetts Institute of Technology. She is a member of the IceCube Collaboration.