Precise limits from lepton flavour violating processes on the Littlest Higgs model with T-parity

TL;DR

This paper recalculates key lepton flavor violating processes in the Littlest Higgs model with T-parity, establishing constraints on the model's parameters based on current experimental limits.

Contribution

It provides a comprehensive recalculation of muon decay processes, including all Goldstone interactions, and derives bounds on the model's effective scale and flavor alignment.

Findings

Effective scale constrained to ~2.5 TeV

Flavor alignment at ~10% level required

Heavy lepton mass splitting must be precise

Abstract

We recalculate the leading one-loop contributions to mu > e gamma and mu -> eee in the Littlest Higgs model with T-parity, recovering previous results for the former. When all the Goldstone interactions are taken into account, the latter is also ultraviolet finite. The present experimental limits on these processes require a somewhat heavy effective scale ~2.5 TeV, or the flavour alignment of the Yukawa couplings of light and heavy leptons at the ~10% level, or the splitting of heavy lepton masses to a similar precision. Present limits on tau decays set no bounds on the corresponding parameters involving the tau lepton