Impact of wave packet separation in low-energy sterile neutrino searches

Light sterile neutrinos have been motivated by anomalies observed in short-baseline neutrino experiments. Among them, radioactive-source and reactor experiments have provided evidence and constraints, respectively, for electron neutrino disappearance compatible with an eV-scale neutrino. The results from these observations are seemingly in conflict. This paper brings into focus the assumption that the neutrino wave packet can be approximated as a plane wave, which is adopted in all analyses of such experiments. We demonstrate that the damping of oscillation due to decoherence effects, e.g., a finite wave packet size, solves the tension between these electron-flavor observations and constraints.

Automated summary

Light sterile neutrinos have been proposed to explain anomalies observed in short-baseline neutrino experiments. Radioactive-source and reactor experiments have provided evidence and constraints for the disappearance of electron neutrinos, suggesting the existence of an eV-scale neutrino. However, these observations seem to be conflicting. This paper investigates the assumption of approximating the neutrino wave packet as a plane wave, showing that the damping of oscillation due to decoherence effects resolves the tension between electron-flavor observations and constraints.