Effect of FCNC mediated Z boson on lepton flavor violating decays

TL;DR

This paper investigates how FCNC mediated Z bosons could enhance lepton flavor violating decays, providing predictions for branching ratios that could be observed in future experiments.

Contribution

It introduces a detailed analysis of LFV decays mediated by FCNC Z bosons, constraining new physics parameters and predicting potentially observable branching ratios.

Findings

Branching ratios for $ au o eee$ and $ au o au ext{phi}$ could reach $10^{-8}$.

LFV B decays like $B_{d,s} o au ext{mu}$ could have branching ratios around $10^{-10}$.

Other LFV B decays are predicted to be too small for near-future detection.

Abstract

We study the three body lepton flavor violating (LFV) decays $\mu^- \to e^- e^+ e^-$, $\tau^- \to l_i^- l_j^+ l_j^-$ and the semileptonic decay $\tau \to \mu \phi $ in the flavor changing neutral current (FCNC) mediated $Z$ boson model. We also calculate the branching ratios for LFV leptonic B decays, $B_{d,s} \to \mu e$, $B_{d,s} \to \tau e$, $B_{d,s} \to \tau \mu$ and the conversion of muon to electron in Ti nucleus. The new physics parameter space is constrained by using the experimental limits on $\mu^- \to e^- e^+ e^-$ and $\tau^- \to \mu^- \mu^+ \mu^-$. We find that the branching ratios for $\tau \to eee $ and $\tau \to \mu \phi$ processes could be as large as $\sim {\cal O}(10^{-8})$ and ${\rm Br}B_{d,s} \to \tau \mu, \tau e) \sim {\cal O}(10^{-10})$. For other LFV B decays the branching ratios are found to be too small to be observed in the near future.