Natural little hierarchy from a partially goldstone twin Higgs

Abstract

We construct a simple theory in which the fine-tuning of the standard model is significantly reduced. Radiative corrections to the quadratic part of the scalar potential are constrained to be symmetric under a global U (4) × U (4) ′ symmetry due to a discrete Z 2 "twin" parity, while the quartic part does not possess this symmetry. As a consequence, when the global symmetry is broken the Higgs fields emerge as light pseudo-Goldstone bosons, but with sizable quartic self-interactions. This structure allows the cutoff scale, Λ, to be raised to the multi-TeV region without significant fine-tuning. In the minimal version of the theory, the amount of fine-tuning is about 15% for Λ = 5 TeV, while it is about 30% in an extended model. This provides a solution to the little hierarchy problem. In the minimal model, the "visible" particle content is exactly that of the two Higgs doublet standard model, while the extended model also contains extra vector-like fermions with masses ≈ (1 ∼ 2) TeV. At the LHC, our minimal model may appear exactly as the two Higgs doublet standard model, and new physics responsible for cutting off the divergences of the Higgs mass-squared parameter may not be discovered. Several possible processes that may be used to discriminate our model from the simple two Higgs doublet model are discussed for the LHC and for a linear collider.

The RG-improved Twin Higgs effective potential at NNLL

“…They are related to the SM fermions and bosons by a discrete Z 2 symmetry which, together with the spontaneous breaking of a global symmetry that turns the Higgs into a pseudo Nambu-Goldstone boson (pNGB), guarantees that the Higgs mass be insensitive to the UV contributions. The resulting possibility of having a natural EWSB with the absence of detectable new physics at the LHC has sparked interest in this class of models in the last years, [6][7][8][9][10][11][12][13][14][15][16][17], but many questions still remain open. In particular, an important problem is to analyze the capability of this scenario to reproduce the observed value of M H , irrespective of any possible UV completion, supersymmetric or composite, of the low-energy Lagrangian.…”

Cosmology in Mirror Twin Higgs and neutrino masses

“…In most familiar realizations of such a symmetry, such as supersymmetry [1,2] or Little Higgs models [3], the top partners are colored, and would therefore be produced at the Large Hadron Collider (LHC) with high rates. The absence of evidence for such particles has led to increasing interest in models based on the framework of Neutral Naturalness [4][5][6][7][8][9][10]. In this class of theories the top partners are not colored, thereby providing a natural explanation for their elusiveness.…”

The spontaneous ℤ 2 $$ {\mathbb{Z}}_2 $$ breaking Twin Higgs

“…Various attempts at addressing this issue can be found in the literature. Reference [22] tries to do so in the context of a two Higgs doublet model…”