Lepton Flavor Violating $l \to l' \gamma$ and $Z \to l \bar l'$ Decays Induced by Scalar Leptoquarks

TL;DR

This paper investigates lepton flavor violating decays induced by scalar leptoquarks, showing they can produce observable signals in current and future experiments, especially in $Z$ boson decays involving tau leptons.

Contribution

It provides a detailed analysis of LFV decays in a scalar leptoquark model, constrained by muon g-2 data, and predicts potential observability of certain $Z$ decay channels.

Findings

Leptoquarks can induce sizable LFV $l o l' \gamma$ decay rates.

Predicted $Br(Z o au^\mp e^\pm)$ reaches current experimental limits.

Future colliders could observe $Br(Z o \mu^\mp au^\pm)$.

Abstract

Motivated by the recent muon $g-2$ data, we study the lepton flavor violating $l \to l' \gamma$ and $Z \to l \bar l'$ ($l, l' = e, \mu, \tau$) decays with $l \neq l'$ in a scalar leptoquark model. Leptoquarks can produce sizable LFV $l\to l'\gamma$ decay rates that can be easily reached by present or near future experiments. % Leptoquark masses and couplings are constrained by the muon $g-2$ data and the current $l \to l' \gamma$ bounds. We predict $Br(Z \to \tau^\mp e^\pm)$ reaching the present limit ($10^{-5}$) and $Br(Z \to \mu^\mp \tau^\pm)$ reaching $2\times 10^{-8}$, which will be accessible by future linear colliders, whereas, the current bounds on LFV impose very strong constraints on the $Br(Z \to \mu^\mp e^\pm)$ and the ratio is too low to be observed in the near future.