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Register a new userHiggs Couplings in Composite Models
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We study Higgs couplings in the composite Higgs model based on the coset SO(5)/SO(4). We show that the couplings to gluons and photons are insensitive to the elementary-composite mixings and thus not affected by light fermionic resonances. Moreover, at leading order in the mixings the Higgs couplings to tops and gluons, when normalized to the Standard Model (SM), are equal. These properties are shown to be direct consequences of the Goldstone symmetry and of the assumption of partial compositeness. In particular, they are independent of the details of the elementary-composite couplings and, under the further assumption of CP invariance, they are also insensitive to derivative interactions of the Higgs with the composite resonances. We support our conclusions with an explicit construction where the SM fermions are embedded in the 14 dimensional representation of SO(5).
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We consider a composite Higgs model based on the $SU(6)/Sp(6)$ coset, where an $U(1)$ subgroup of $Sp(6)$ is identified as the flavor symmetry. A complex scalar field $s$, which is a pseudo-Nambu-Goldstone boson of the broken symmetry, carries a flavor charge and plays the role of a flavon field. The $U(1)_F$ flavor symmetry is then broken by a VEV of the flavon field, which leads to a small parameter and generates the mass hierarchy between the top and bottom quarks. A light flavon below the TeV scale can be naturally introduced, which provides a fully testable model for the origin of flavor hierarchy. A light flavon also leads to substantial flavor changing neutral currents, which are strongly constrained by the flavor precision tests. The direct search of additional scalar bosons can also be conducted in HL-LHC and future hadron colliders.
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.
Mass-split composite Higgs models naturally accommodate the experimental observation of a light 125 GeV Higgs boson and predict a large scale separation to other heavier resonances. We explore the SU(3) gauge system with four light (massless) and six heavy (massive) flavors by performing numerical simulations. Since the underlying system with degenerate and massless ten flavors appears to be infrared conformal, this system inherits conformal hyperscaling and allows to study near-conformal dynamics. Carrying out nonperturbative lattice field theory simulations, we present the low-lying particle spectrum. We demonstrate hyperscaling, predict the anomalous mass dimension of the corresponding conformal fixed point, and show that in the investigated mass regime the data are described by dilaton chiral perturbation theory. The proximity of a conformal infrared fixed point leads to a highly predictive particle spectrum which is quite distinct from QCD. Further we present initial results of our finite temperature investigations.
Fermionic third generation top partners are generic in composite Higgs models. They are likely to decay into third generation quarks and electroweak bosons. We propose a novel cut-and-count-style analysis in which we cross correlate the model-dependent single and model-independent pair production processes for the top partners $X_{5/3}$ and $B$. In the class of composite Higgs models we study, $X_{5/3}$ is very special as it is the lightest exotic fermion. A constraint on the mass of $X_{5/3}$ directly extends to constrains on all top partner masses. By combining jet substructure methods with conventional reconstruction techniques we show that in this kind of final state a smooth interpolation between the boosted and unboosted regime is possible. We find that a reinterpretation of existing searches can improve bounds on the parameter space of composite Higgs models. Further, at 8 TeV a combined search for $X_{5/3}$ and $B$ in the $l+rm{jets}$ final state can be more sensitive than a search involving same-sign dileptons.
We present a composite scotogenic model for neutrino masses, which are generated via loops of $mathbb{Z}_2$-odd composite scalars. We consider three different approaches to the couplings of the neutrinos (including three right-handed singlets) and the composite sector: ETC-like four-fermion interactions, fundamental partial compositeness and fermion partial compositeness. In all cases, the model can feature sizeable couplings and remain viable with respect to various experimental constraints if the three $ mathbb{Z}_2 $-odd right-handed neutrinos have masses between the TeV and the Planck scales. Additionally, the lightest $mathbb{Z}_2$-odd composite scalar may play the role of Dark Matter, either via thermal freeze-out or as an asymmetric relic. This mechanism can be featured in a variety of models based on vacuum misalignment. For concreteness, we demonstrate it in a composite two-Higgs scheme based on the coset SU(6)/Sp(6).
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