Radiative and flavor-violating transitions of leptons from interactions with color-octet particles

TL;DR

This paper investigates how interactions between leptons and color-octet particles could generate neutrino masses, analyzing flavor-violating lepton decays to constrain these interactions and exploring implications for collider experiments.

Contribution

It provides a systematic analysis of Yukawa coupling flavor structure, a parametrization, and explores the interplay between rare lepton decays and collider physics constraints.

Findings

Muon decays impose strict constraints on couplings.

Most tau decays are below current experimental sensitivity.

Certain parameter regions allow tau decays to be near current detection levels.

Abstract

It has been recently proposed that neutrino mass could originate from Yukawa interactions of leptons with new colored particles. This raises the interesting possibility of testing mass generation through copious production of those particles at hadron colliders. A realistic assessment of it however should take into account how large those interactions could be from available precision results. In this work we make a systematic analysis to the flavor structure in Yukawa couplings, provide a convenient parametrization to it, and investigate the rare radiative and pure leptonic decays of the muon and tau leptons. For general values of parameters the muon decays set stringent constraints on the couplings, and all rare tau decays are far below the current experimental sensitivity. However, there is room in parameter space in which the muon decays could be significantly suppressed by destructive interference between colored particles without generically reducing the couplings themselves. This is also the region of parameters that is relevant to collider physics. We show that for this part of parameter space some tau decays can reach or are close to the current level of precision.