Improving fine-tuning in composite Higgs models

Abstract

In this paper we investigate the next-to-minimal composite Higgs model with a SO(6)/SO(5) coset, whose pNGB sector includes a Standard Model singlet in addition to the usual Higgs doublet. The fermions are embedded in the representation 6 of SO(6). We study the region of parameter space of the model where the radiatively generated potential has global minima with both the doublet and the singlet fields developing vacuum expectation values. We investigate the consequences of kinetic and mass mixing between the Higgs and the singlet scalar that arise in this framework. We demonstrate that the ensuing doublet-singlet mixing can provide a handle to accommodate heavier resonances (top-partners) for a given compositeness scale as compared to the minimal composite Higgs model, thus relaxing the tension with the direct LHC bounds. The main phenomenological consequence of this is a sizable deviation of the Higgs couplings from the Standard Model predictions. While the present experimental precision in the measurement of the Higgs couplings still allows for considerable release of this tension, future measurements of the Higgs branching ratios with increased precision would lead to stringent constraints on this setup.

Electroweak phase transition with composite Higgs models: calculability, gravitational waves and collider searches

“…[42] proposes the MHP hypothesis, which assumes the UV contributions are negligible due to some unknown mechanism of the underlying theory. MHP has been generally adopted in the studies of CHMs [11,[42][43][44][45]. However, as we will demonstrate, under MHP all three NMCHMs we consider fail to trigger SFOEWPT.…”

“…unknown mechanisms of the underlying theory [11,[42][43][44][45]. This is known as the minimal Higgs potential hypothesis (MHP), first clearly proposed in Ref.…”

Classification of NLO operators for composite Higgs models

“…This mixing, which is only physical in theories with explicit CP-violation, has been used in Ref. [89] to reduce the fine-tuning in the Higgs mass.…”

Vacuum misalignment and pattern of scalar masses in the SU(5)/SO(5) composite Higgs model

“…1 However, especially in models where many neutral pNGBs are present, a more general vacuum structure cannot be excluded a priori neither by electroweak precision data, specifically the bounds on the T parameter, nor by the measurement of Higgs couplings. In fact, the vacuum misalignment is 1 Mixing of the Higgs to other light scalars can be induced by adding ad-hoc couplings, like in Refs [10,11], or by misaligning the vacuum in non-minimal ways, as shown in Ref. [9].…”