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

TL;DR

This paper proposes using lepton-flavor-violating scattering processes involving hyperons to probe new physics, analyzing polarization observables to distinguish model uncertainties and chiral interactions.

Contribution

It introduces a novel approach to study lepton-flavor violation via hyperon production and analyzes polarization observables to identify new physics signatures.

Findings

Polarization observables can differentiate form factor models.

Event rate predictions vary widely depending on model assumptions.

Polarization measurements can reveal the chiral nature of new physics interactions.

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.