Bounds on the Simplest Little Higgs Model Mass Spectrum Through Z Leptonic Decay

TL;DR

This paper analyzes the simplest little Higgs model's mass spectrum by deriving leptonic neutral currents and using electroweak data to set bounds on new gauge boson masses and model parameters.

Contribution

It provides the first detailed bounds on the energy scale and gauge boson masses in the simplest little Higgs model based on Z leptonic decay data.

Findings

Lower bound on the model scale: f ≥ 5.6 TeV

Lower bounds on new gauge boson masses: W' ≥ 2.6 TeV, Z' ≥ 3.1 TeV

Constraints on model parameters k and μ for Higgs mass range

Abstract

We derive the leptonic neutral current in the simplest little Higgs model and compute the contribution of the model to the decay width $Z \to e^+e^-$. Using the precision electroweak data we obtain a strong lower bound $f\geq 5.6$ TeV at 95% C.L. on the characteristic energy scale of the model. It results in a lower bound for the new gauge bosons $W^{\prime\pm}$ and $Z^{\prime}$ as being $M_{W^{\prime\pm}}\geq 2.6$ TeV and $M_{Z^{\prime}}\geq 3.1$ TeV, respectively. We also present the allowed values of the $k=f_1/f_2$ which is the parameter relating the two vacuum expectation values of the scalar triplets in the model, and the $\mu$ parameter of a quadratic term, involving the triplets, necessary to provide an acceptable mass range for the standard Higgs boson.