Rare Z Decays and Neutrino Flavor Universality

TL;DR

This paper investigates rare Z-boson decays involving neutrinos and charged leptons, highlighting their potential to test neutrino flavor universality with high precision at future colliders.

Contribution

It introduces a novel approach to probe Z-neutrino couplings through rare four-body Z decays, emphasizing interference effects and flavor sensitivity.

Findings

Decays are highly sensitive to Z-neutrino coupling deviations.

Future colliders could measure these decays with percent-level accuracy.

Interference effects significantly influence decay rates.

Abstract

We study rare four-body decays of the Z-boson involving at least one neutrino and one charged lepton. Large destructive interferences make these decays very sensitive to the Z couplings to neutrinos. As the identified charged leptons can determine the neutrino flavors, these decays probe the universality of the Z couplings to neutrinos. The rare four-body processes could be accurately measured at future lepton colliders, leading to percent level precision.