Exact one-loop results for $l_i \to l_j\gamma$ in 3-3-1 models

TL;DR

This paper provides exact analytical calculations for lepton flavor-violating decays in 3-3-1 models, revealing significant effects of exotic leptons and interference phenomena on decay rates, which are crucial for experimental constraints.

Contribution

It offers the first full analytical results for $l_i o l_j o ext{gamma}$ decays in 3-3-1 models with arbitrary exotic lepton charges, including external lepton masses.

Findings

Branching fractions can reach experimental limits with large mixings and mass differences.

Destructive interference between gauge and Higgs contributions can significantly suppress decay rates.

Exact results differ notably from approximate calculations neglecting external lepton masses.

Abstract

We investigate the decays $l_i\rightarrow l_j \gamma$, with $l_i=e,\mu,\tau$ in a general class of 3-3-1 models with heavy exotic leptons with arbitrary electric charges. We present full and exact analytical results keeping external lepton masses. As a by product, we perform numerical comparisons between exact results and approximate ones where the external lepton masses are neglected. As expected, we found that branching fractions can reach the current experimental limits if mixings and mass differences of the exotic leptons are large enough. We also found unexpectedly that, depending on the parameter values, there can be huge destructive interference between the gauge and Higgs contributions when the gauge bosons connecting the Standard Model leptons to the exotic leptons are light enough. This mechanism should be taken into account when using experimental constraints on the branching fractions to exclude the parameter space of the model.