Composite Higgs Models after Run 2

Abstract

We assess the status of models in which the Higgs is a composite pseudo-Nambu Goldstone boson, in the light of the latest 13 TeV Run 2 Higgs data. Drawing from the extensive Composite Higgs literature, we collect together predictions for the modified couplings of the Higgs, in particular examining the different predictions for κV and κF . Despite the variety and increasing complexity of models on the market, we point out that many independent models make identical predictions for these couplings. We then look into further corrections induced by tree-level effects such as massmixing and singlet VEVs. We then investigate the compatibility of different models with the data, combining the Run 1 and recent Run 2 LHC data. We obtain a robust limit on the scale f of 600 GeV, with stronger limits for different choices of fermion embeddings. We also discuss how a deficit in a Higgs channel could pinpoint the type of Composite Higgs model responsible for it.

Current and future constraints on Higgs couplings in the nonlinear Effective Theory

“…From the intersection with the 95% probability JHEP07 (2018) contours of current Higgs limits, we find that the parameter ξ cannot exceed 0.22 (0.12) in the model CHM-4 (CHM-5). This bound stems from the Higgs coupling to t and b (t) and can be translated into a minimal new-physics scale f of 530 (710) GeV, in agreement with [158]. Moving onto the expected sensitivities at future colliders, we can use the projected experimental limits on the parameters in figure 6 to quantify the attainable impact on composite Higgs scenarios.…”

Signals of the electroweak phase transition at colliders and gravitational wave observatories

“…Since ξ = O(0.1 − 0.2) [1,50,98,99], effects of O(ξ 2 ) could in principle be larger than the O(1/16π 2 ) effects. The leading effects in the double expansion are then given by expanding L LO up to O(ξ 2 ).…”

Constraining composite Higgs models using LHC data

“…The next-to-minimal model, with SO(6)/SO(5) coset includes a real singlet scalar (η) along with the usual Higgs doublet. Quite a few interesting features emerge in this case, depending on whether η acquires a vev [21,43,44] or not [70][71][72][73]. In the present section we discuss the effect of the η-vev and consequently the doublet-singlet scalar mixing on the Yukawa couplings.…”

“…where θ mix denotes the amount of mixing and is constrained by the LHC Higgs data. For the case, where both m η m h and η h , the mixing angle can be simply parametrized as [44] θ mix ∼ h η m 2 η 1 .…”