A Little Twin Higgs Model

TL;DR

This paper introduces a twin Higgs model with enhanced symmetry protections that reduces fine-tuning in the Higgs mass, using a left-right symmetry framework with two Z_2 parities.

Contribution

The model extends symmetry to include two Z_2 parities, protecting the Higgs from quadratic divergences at one loop and significantly reducing fine-tuning.

Findings

Quadratic divergences are protected at one loop.

Fine tuning is substantially reduced compared to previous models.

Applicable to mirror twin Higgs models with a massless mirror photon.

Abstract

We present a twin Higgs model based on left-right symmetry with a tree level quartic. This is made possible by extending the symmetry of the model to include two Z_2 parities, each of which is sufficient to protect the Higgs from getting a quadratically divergent mass squared. Although both parities are broken explicitly, the symmetries that protect the Higgs from getting a quadratically divergent mass are broken only collectively. The quadratic divergences of the Higgs mass are thus still protected at one loop. We find that the fine tuning in this model is reduced substantially compared to the original left-right twin Higgs model. This mechanism can also be applied to the mirror twin Higgs model to get a significant reduction of the fine tuning, while keeping the mirror photon massless.