Abstract

The phenomenon of neutrino flavor oscillations motivates searches for sterile neutrinos in a broad range of masses and mixing-parameter values. A sterile neutrino N that mixes predominantly with the tau neutrino is particularly challenging experimentally. To address this challenge, we propose a new method to search for a nu(tau)-mixing N that is lighter than the tau lepton. The method uses the large e(+)e(-) -> tau(+)tau(-) samples collected at B-factory experiments to produce the N in tau-lepton decays. We exploit the long lifetime of a sterile neutrino in this mass range to suppress background and apply kinematic and vertexing constraints that enable measuring the sterile-neutrino mass. Estimates for the sensitivities of the BABAR, Belle, and Belle II experiments are calculated and presented.