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Chala, M., Durieux, G., Grojean, C., de Lima, L., & Matsedonskyi, O. (2017). Minimally extended SILH. J. High Energy Phys., 06(6), 088–32pp.
Abstract: Higgs boson compositeness is a phenomenologically viable scenario addressing the hierarchy problem. In minimal models, the Higgs boson is the only degree of freedom of the strong sector below the strong interaction scale. We present here the simplest extension of such a framework with an additional composite spin-zero singlet. To this end, we adopt an effective field theory approach and develop a set of rules to estimate the size of the various operator coefficients, relating them to the parameters of the strong sector and its structural features. As a result, we obtain the patterns of new interactions affecting both the new singlet and the Higgs boson's physics. We identify the characteristics of the singlet field which cause its effects on Higgs physics to dominate over the ones inherited from the composite nature of the Higgs boson. Our effective field theory construction is supported by comparisons with explicit UV models.
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Chala, M., Krause, C., & Nardini, G. (2018). Signals of the electroweak phase transition at colliders and gravitational wave observatories. J. High Energy Phys., 07(7), 062–29pp.
Abstract: If the electroweak phase transition (EWPT) is of strongly first order due to higher dimensional operators, the scale of new physics generating them is at the TeV scale or below. In this case the effective-field theory (EFT) neglecting operators of dimension higher than six may overlook terms that are relevant for the EWPT analysis. In this article we study the EWPT in the EFT to dimension eight. We estimate the reach of the future gravitational wave observatory LISA for probing the region in which the EWPT is strongly first order and compare it with the capabilities of the Higgs measurements via double-Higgs production at current and future colliders. We also match different UV models to the previously mentioned dimension-eight EFT and demonstrate that, from the top-down point of view, the double-Higgs production is not the best signal to explore these scenarios.
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Chowdhury, D., & Eberhardt, O. (2018). Update of global Two-Higgs-Doublet model fits. J. High Energy Phys., 05(5), 161–42pp.
Abstract: We perform global fits of Two-Higgs-Doublet models with a softly broken Z(2) symmetry to recent results from the LHC detectors CMS and ATLAS, that is signal strengths and direct search limits obtained at root s = 8 TeV and root s = 13 TeV. We combine all available ATLAS and CMS constraints with the other relevant theoretical and experimental bounds and present the latest limits on the model parameters. We obtain that deviations from the so-called alignment limit beta-alpha = pi/2 cannot be larger than 0.03 in type I and have to be smaller than 0.02 in the remaining three types. For the latter, we also observe lower limits on the heavy Higgs masses in the global fit. The splittings between these masses cannot exceed 200 GeV in the types I and X and 130 GeV in the types II and Y. Finally, we find that the decay widths of the heavy Higgs particles cannot be larger than 7% of their masses if they are lighter than 1.5 TeV.
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Davidson, S., Felipe, R. G., Serodio, H., & Silva, J. P. (2013). Baryogenesis through split Higgsogenesis. J. High Energy Phys., 11(11), 100–22pp.
Abstract: We study the cosmological evolution of asymmetries in the two-Higgs doublet extension of the Standard Model, prior to the electroweak phase transition. If Higgs flavour-exchanging interactions are sufficiently slow, then a relative asymmetry among the Higgs doublets corresponds to an effectively conserved quantum number. Since the magnitude of the Higgs couplings depends on the choice of basis in the :Higgs doublet space, we attempt to formulate basis-independent out-of-equilibrium conditions. We show that an initial asymmetry between the fliggs scalars, which could be generated by GP violation in the :Higgs sector, will be transformed into a baryon asymmetry by the sphalerons, without the need of B – L violation. This novel mechanism of baryogenesis through (split) Higgsogenesis is exemplified with simple scenarios based on the out-of-equilibrium decay of heavy singlet scalar fields into the illiggs doublets.
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de Blas, J., Eberhardt, O., & Krause, C. (2018). Current and future constraints on Higgs couplings in the nonlinear Effective Theory. J. High Energy Phys., 07(7), 048–45pp.
Abstract: We perform a Bayesian statistical analysis of the constraints on the nonlinear Effective Theory given by the Higgs electroweak chiral Lagrangian. We obtain bounds on the effective coefficients entering in Higgs observables at the leading order, using all available Higgs-boson signal strengths from the LHC runs 1 and 2. Using a prior dependence study of the solutions, we discuss the results within the context of natural-sized Wilson coefficients. We further study the expected sensitivities to the different Wilson coefficients at various possible future colliders. Finally, we interpret our results in terms of some minimal composite Higgs models.
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