A Weakly Coupled Ultraviolet Completion of the Littlest Higgs with T-parity

TL;DR

This paper presents a renormalizable ultraviolet completion of the Littlest Higgs model with T-parity, addressing the little hierarchy problem and ensuring anomaly freedom, while maintaining compatibility with electroweak precision tests.

Contribution

It introduces a weakly coupled, anomaly-free UV completion of the LHT based on an SU(5)xSU(2)xU(1) gauge theory with a Z_2 symmetry, reproducing the LHT structure below 10 TeV.

Findings

Model is free of anomalies including gauge, gravitational, and T-parity anomalies.

Additional states at TeV scale impact electroweak precision observables.

Model can be embedded into supersymmetric or warped extra-dimensional frameworks.

Abstract

We construct a weakly coupled, renormalizable ultraviolet completion of the Littlest Higgs model with T-parity (LHT), based on an SU(5)xSU(2)xU(1) gauge theory with a discrete Z_2 symmetry. Our model reproduces the complete structure of the LHT below the 10 TeV scale, including the collective symmetry breaking mechanism which solves the little hierarchy problem. The model is manifestly free of anomalies, including both gauge/gravitational anomalies and anomalies involving T-parity. At the TeV scale, the model contains additional states not present in the LHT. We estimate the impact of these states on precision electroweak observables, and show that the model is realistic. We also discuss how our model can be embedded into a supersymmetric theory or a five-dimensional setup with a warped extra dimension, stabilyzing the hierarchy between the 10 TeV and the Planck scale.