Lepton Flavor Violation in Little Higgs Models

TL;DR

This paper investigates lepton flavor violation processes in Little Higgs models, calculating branching ratios and conversion rates, and compares predictions with experimental limits to constrain model parameters.

Contribution

It provides the first detailed calculations of LFV processes in Littlest Higgs with T-parity and Simplest Little Higgs models, including Feynman rules and leading-order predictions.

Findings

Current experimental constraints impose lower bounds on the symmetry breaking scale f.

SLH models face more stringent constraints than LHT models.

To satisfy limits, models require high f, lepton sector alignment, or degenerate heavy leptons.

Abstract

We report on our study of the LFV processes \mu \to e\gamma, \mu\to eee and \mu \to e conversion in the context of Little Higgs models. Specifically we examine the Littlest Higgs with T-parity (LHT) and the Simplest Little Higgs (SLH) as examples of a Product group and Simple group Little Higgs models respectively. The necessary Feynman rules for both models are obtained in the 't Hooft Feynman Gauge up to order v^2/f^2 and predictions for the branching ratios and conversion rates of the LFV processes are calculated to leading order (one-loop level). Comparison with current experimental constraints show that there is some tension and, in order to be within the limits, one requires a higher breaking scale f, alignment of the heavy and light lepton sectors or almost degenerate heavy lepton masses. These constraints are more demanding in the SLH than in the LHT case.