Abstract
We give an explicit example of a composite Higgs model with a pseudo-Nambu-Goldstone Higgs in which the top Yukawa coupling is generated via the partial compositeness mechanism. This mechanism requires composite top partners which are relatively light compared to the typical mass scale of the strongly coupled theory. While most studies of the phenomenology of such models have focused on a bottom-up approach with a minimal effective theory, a top-down approach suggests that the theory should contain a limit in which an unbroken global chiral symmetry protects the mass of the top partners, and the spectrum of the partners satisfies ‘t Hooft matching conditions. We find that the relatively light fermions and pseudo-Goldstone bosons fall into complete multiplets of a large approximate global symmetry, and that the spectrum of particles lighter than a few TeV is non-minimal. Our example illustrates the likely features of a such a composite Higgs theory and also serves as an example of a non-chiral theory with a possible solution to the ‘t Hooft matching conditions. We find in this example that for some low-energy parameters in the effective theory the top partners can decay into high-multiplicity final states, which could be difficult for the Large Hadron Collider (LHC) to constrain. This may potentially allow for the top partners to be lighter than those in more minimal models.
Highlights
Higgs is that it is an approximate Nambu-Goldstone boson, whose mass is protected by an approximate non-linearly realized symmetry
While most studies of the phenomenology of such models have focused on a bottom-up approach with a minimal effective theory, a top-down approach suggests that the theory should contain a limit in which an unbroken global chiral symmetry protects the mass of the top partners, and the spectrum of the partners satisfies ‘t Hooft matching conditions
Our example illustrates the likely features of a such a composite Higgs theory and serves as an example of a non-chiral theory with a possible solution to the ‘t Hooft matching conditions. We find in this example that for some low-energy parameters in the effective theory the top partners can decay into high-multiplicity final states, which could be difficult for the Large Hadron Collider (LHC) to constrain
Summary
Our composite pseudo-Nambu-Goldstone Higgs model is based on the SU(4)/Sp(4) symmetry-breaking pattern [6] of the “Intermediate” composite Higgs model [7]. We expect that in the highly non-supersymmetric limit in which the scalar masses which are heavy compared to the compositeness scale, the chiral global symmetries of the theory will spontaneously break to a subgroup which allows fermion masses. In order to produce a pseudo-Goldstone Higgs and masses for the top partners, the SU(10) symmetry must spontaneously break We assume this breaking scale is lower than the compositeness scale, which requires that even in the absence of symmetry breaking, the theory contains a relatively light scalar multiplet with a non-trivial SU(10) transformation. A SU(6) × SU(4) global symmetry structure was previously studied in the context of a Sp(6) gauge group in [15], but this work did not give a dynamical explanation for the mass and couplings of the top partner, which is provided here by the SU(10) breaking. That work assumed a different condensate structure that breaks the global SU(6) to SO(6), rather than the Sp(6) that we will find, as well as having the composite fermions in a different representation of the global SU(6) × SU(4)
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