Abstract

We investigate charged lepton flavor violating processes $\mu\rightarrow e \gamma$, $\mu\rightarrow e e \overline{e}$ and $\mu-e$ conversion in nuclei for a class of three-loop radiative neutrino mass generation models with electroweak multiplets of increasing order. We find that, because of certain cancellations among various one-loop diagrams which give the dipole and non-dipole contributions in effective $\mu e \gamma$ vertex and Z-penguin contribution in effective $\mu e Z$ vertex, the flavor violating processes $\mu\rightarrow e\gamma$ and $\mu-e$ conversion in nuclei become highly suppressed compared to $\mu\rightarrow e e \overline{e}$ process. Therefore, the observation of such pattern in LFV processes may reveal the radiative mechanism behind neutrino mass generation.

Highlights

  • We have observed lepton flavor violation (LFV) in the neutral fermion sector of the Standard Model (SM) in neutrino oscillation, the charged LFV in the SM has turned out to be highly suppressed

  • Many physics beyond the standard model (BSM) scenario, especially new physics related to the generation and smallness of the neutrino mass, can lead to unsuppressed charged LFV processes [2,6,7].1 which are within the reach of currently operating and future experiments

  • III, we describe the relevant formulas of charged LFV processes μ → eγ, μ → eee, and μ − e conversion rate in nuclei in a generalized KNT model

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Summary

INTRODUCTION

We have observed lepton flavor violation (LFV) in the neutral fermion sector of the Standard Model (SM) in neutrino oscillation, the charged LFV in the SM has turned out to be highly suppressed. Many physics beyond the standard model (BSM) scenario, especially new physics related to the generation and smallness of the neutrino mass, can lead to unsuppressed charged LFV processes [2,6,7].1 which are within the reach of currently operating and future experiments. No Yukawa terms with a SM fermion that give rise to the Dirac neutrino mass, are allowed in the Lagrangian if the KNT particle content is extended with Φ that has ðjφ; YφÞ 1⁄4 ð2; 1Þ and Fi with ðjF; YFÞ 1⁄4 ð2; 0Þ to. Appendix contains the loop functions used in calculations of charged LFV processes

The field content
Mass splittings in the multiplets
Three-loop radiative neutrino mass
CHARGED LEPTON FLAVOR VIOLATING PROCESSES
Z-penguin contribution
Viable parameter space
Charged LFV processes
CONCLUSION AND OUTLOOK
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