Minimal Mirror Twin Higgs

TL;DR

This paper proposes a minimal Mirror Twin Higgs model with broken Z2 symmetry in Yukawa couplings, reducing fine-tuning and predicting observable signals in Higgs decays, dark matter detection, and dark radiation.

Contribution

It introduces a minimal effective field theory with Z2 breaking in Yukawa couplings, addressing the little hierarchy problem and linking it to testable experimental signatures.

Findings

Fine-tuning for electroweak scale is 10-50%.

Predicts signals in Higgs decays, dark matter detection, and dark radiation.

Considers mirror neutrons and self-interacting mirror atoms as dark matter candidates.

Abstract

In a Mirror Twin World with a maximally symmetric Higgs sector the little hierarchy of the Standard Model can be significantly mitigated, perhaps displacing the cutoff scale above the LHC reach. We show that consistency with observations requires that the Z2 parity exchanging the Standard Model with its mirror be broken in the Yukawa couplings. A minimal such effective field theory, with this sole Z2 breaking, can generate the Z2 breaking in the Higgs sector necessary for the Twin Higgs mechanism. The theory has constrained and correlated signals in Higgs decays, direct Dark Matter Detection and Dark Radiation, all within reach of foreseen experiments, over a region of parameter space where the fine-tuning for the electroweak scale is 10-50%. For dark matter, both mirror neutrons and a variety of self-interacting mirror atoms are considered. Neutrino mass signals and the effects of a possible additional Z2 breaking from the vacuum expectation values of B-L breaking fields are also discussed.