The Flavor of the Composite Twin Higgs

TL;DR

Composite twin Higgs models alleviate flavor-related tuning issues in Higgs potential by leveraging twin partners and higher composite scales, improving flavor bounds compared to traditional composite Higgs models.

Contribution

This paper demonstrates how composite twin Higgs models reduce flavor constraints and tuning, expanding viable parameter space with near-strong coupling composites.

Findings

CTH models better accommodate anarchic flavor than CH models.

Flavor bounds are dominated by KK Z exchange and KK fermion loops.

Numerical analysis confirms reduced flavor tension in CTH models.

Abstract

The assumption of anarchic quark flavor puts serious stress on composite Higgs models: flavor bounds imply a tuning of a few per-mille (at best) in the Higgs potential. Composite twin Higgs (CTH) models significantly reduce this tension by opening up a new region of parameter space, obtained by raising the coupling among the composites close to the strong coupling limit $g_* \sim 4\pi$, thereby raising the scale of composites to around 10 TeV. This does not lead to large tuning in the Higgs potential since the leading quantum corrections are canceled by the twin partners (rather than the composites). We survey the leading flavor bounds on the CTH, which correspond to tree-level $\Delta F=2$ four-Fermi operators from Kaluza-Klein (KK) Z exchange in the kaon system and 1-loop corrections from KK fermions to the electric dipole moment of the neutron. We provide a parametric estimate for these bounds and also perform a numeric scan of the parameter space using the complete calculation for both quantities. The results confirm our expectation that CTH models accommodate anarchic flavor significantly better than regular composite Higgs (CH) models. Our conclusions apply both to the identical and fraternal twin cases.