Polarization Probes of New Physics in Lepton-Flavor-Violating Hyperon Production from $e^- N \to \tau^- Y$ Scattering

Abstract

While charged lepton-flavor-violating tau decays to strange mesons provide powerful probes of the underlying $\tau\to\ell d \bar{s}$ transition, the corresponding decay modes involving hyperons are kinematically forbidden. To address this gap, we propose the quasi-elastic scattering processes $e^- N \to \tau^- Y$. Within a general low-energy effective Lagrangian, we perform a comprehensive analysis of the final-state polarizations of both the $\tau$ lepton and the hyperon $Y$, systematically addressing the theoretical uncertainty driven by the model dependence of form factors. Our analysis demonstrates that while this uncertainty leads to large variations in predicted rates, the polarization observables can potentially distinguish between the form factor models, and help to determine the chiral nature of the vectorial new physics interaction. Finally, we forecast the event rates for future facilities, revealing a strong dependence on the form factor models, with predicted yields ranging from potentially observable levels to rates far below current detection thresholds.