Little Higgs Review

TL;DR

The paper surveys Little Higgs theories as a natural extension of the Standard Model in which the Higgs is a pseudo-Nambu-Goldstone boson. It explains the mechanism of collective symmetry breaking that cancels one-loop quadratic divergences and details concrete SU3 based constructions, including the Simple SU3 model, Minimal Moose, and Littlest Higgs, with phenomenology at the TeV scale. It outlines the gauge, Yukawa, and quartic sectors that realize the mechanism, discusses precision electroweak constraints, and highlights collider signatures for TeV-scale partners. It also surveys variants and UV completions, including custodial symmetry protected models and T-parity, and discusses implications for LHC tests and potential dark matter candidates.

Abstract

Recently there has been renewed interest in the possibility that the Higgs particle of the Standard Model is a pseudo-Nambu-Goldstone boson. This development was spurred by the observation that if certain global symmetries are broken only by the interplay between two or more coupling constants, then the Higgs mass-squared is free from quadratic divergences at one loop. This "collective symmetry" breaking is the essential ingredient in little Higgs theories, which are weakly coupled extensions of the Standard Model with little or no fine tuning, describing physics up to an energy scale ~10 TeV. Here we give a pedagogical introduction to little Higgs theories. We review their structure and phenomenology, focusing mainly on the SU(3) theory, the Minimal Moose, and the Littlest Higgs as concrete examples.

Figures (9)

• Figure 1: The most significant quadratically divergent contributions to the Higgs mass in the Standard Model.
• Figure 2: The "Mexican hat" potential for $\Phi$. The black dot represents the vacuum expectation value $f$, $r$ is the radial mode and $\theta$ the Nambu-Goldstone boson.
• Figure 3: Quadratically divergent gauge loop contributions to the Higgs mass.
• Figure 4: a.) Quadratically divergent gauge loop contributions which do not contribute to the Higgs potential, b.) log-divergent contribution to the Higgs mass.
• Figure 5: The quadratically divergent contribution to the Higgs mass from the top loop is canceled by the $T$ loop.