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Botella, F. J., Branco, G. C., & Rebelo, M. N. (2010). Minimal flavour violation and multi-Higgs models. Phys. Lett. B, 687(2-3), 194–200.
Abstract: We propose an extension of the hypothesis of Minimal Flavour Violation (MFV) to general multi-Higgs models without the assumption of Natural Flavour Conservation (NFC) in the Higgs sector. We study in detail under what conditions the neutral Higgs couplings are only functions of V-CKM and propose a MFV expansion for the neutral Higgs couplings to fermions.
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Carcamo Hernandez, A. E., Vishnudath, K. N., & Valle, J. W. F. (2023). Linear seesaw mechanism from dark sector. J. High Energy Phys., 09(9), 046–18pp.
Abstract: We propose a minimal model where a dark sector seeds neutrino mass generation radiatively within the linear seesaw mechanism. Neutrino masses are calculable, since treelevel contributions are forbidden by symmetry. They arise from spontaneous lepton number violation by a small Higgs triplet vacuum expectation value. Lepton flavour violating processes e.g. μ-> e gamma can be sizeable, despite the tiny neutrino masses. We comment also on dark-matter and collider implications.
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Carrasco, J., & Zurita, J. (2024). Emerging jet probes of strongly interacting dark sectors. J. High Energy Phys., 01(1), 034–23pp.
Abstract: A strongly interacting dark sector can give rise to a class of signatures dubbed dark showers, where in analogy to the strong sector in the Standard Model, the dark sector undergoes its own showering and hadronization, before decaying into Standard Model final states. When the typical decay lengths of the dark sector mesons are larger than a few centimeters (and no larger than a few meters) they give rise to the striking signature of emerging jets, characterized by a large multiplicity of displaced vertices.In this article we consider the general reinterpretation of the CMS search for emerging jets plus prompt jets into arbitrary new physics scenarios giving rise to emerging jets. More concretely, we consider the cases where the SM Higgs mediates between the dark sector and the SM, for several benchmark decay scenarios. Our procedure is validated employing the same model than the CMS emerging jet search. We find that emerging jets can be the leading probe in regions of parameter space, in particular when considering the so-called gluon portal and dark photon portal decay benchmarks. With the current 16.1 fb-1 of luminosity this search can exclude down to O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathcal{O} $$\end{document}(20)% exotic branching ratio of the SM Higgs, but a naive extrapolation to the 139 fb-1 luminosity employed in the current model-independent, indirect bound of 16 % would probe exotic branching ratios into dark quarks down to below 10 %. Further extrapolating these results to the HL-LHC, we find that one can pin down exotic branching ratio values of 1%, which is below the HL-LHC expectations of 2.5-4 %. We make our recasting code publicly available, as part of the LLP Recasting Repository.
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Celis, A., Ilisie, V., & Pich, A. (2013). LHC constraints on two-Higgs doublet models. J. High Energy Phys., 07(7), 053–44pp.
Abstract: A new Higgs-like boson with mass around 126 GeV has recently been discovered at the LHC. The available data on this new particle is analyzed within the context of two-Higgs doublet models without tree-level flavour-changing neutral currents. Keeping the generic Yukawa structure of the Aligned Two-Higgs Doublet Model framework, we study the implications of the LHC data on the allowed scalar spectrum. We analyze both the CP-violating and CP-conserving cases, and a few particular limits with a reduced number of free parameters, such as the usual models based on discrete Z(2) symmetries.
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Celis, A., Ilisie, V., & Pich, A. (2013). Towards a general analysis of LHC data within two-Higgs-doublet models. J. High Energy Phys., 12(12), 095–32pp.
Abstract: The data accumulated so far confirm the Higgs-like nature of the new boson discovered at the LHC. The Standard Model Higgs hypothesis is compatible with the collider results and no significant deviations from the Standard Model have been observed neither in the flavour sector nor in electroweak precision observables. We update the LHC and Tevatron constraints on CP-conserving two-Higgs-doublet models without tree-level flavour-changing neutral currents. While the relative sign between the top Yukawa and the gauge coupling of the 126 GeV Higgs is found be the same as in the SM, at 90% CL, there is a sign degeneracy in the determination of its bottom and tau Yukawa couplings. This results in several disjoint allowed regions in the parameter space. We show how generic sum rules governing the scalar couplings determine the properties of the additional Higgs bosons in the different allowed regions. The role of electroweak precision observables, low-energy flavour constraints and LHC searches for additional scalars to further restrict the available parameter space is also discussed.
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Centelles Chulia, S., Doring, C., Rodejohann, W., & Saldana-Salazar, U. J. (2020). Natural axion model from flavour. J. High Energy Phys., 09(9), 137–29pp.
Abstract: We explore a common symmetrical origin for two long standing problems in particle physics: the strong CP and the fermion mass hierarchy problems. The Peccei-Quinn mechanism solves the former one with an anomalous global U(1)(PQ) symmetry. Here we investigate how this U(1)(PQ) could at the same time explain the fermion mass hierarchy. We work in the context of a four-Higgs-doublet model which explains all quark and charged fermion masses with natural, i.e. order 1, Yukawa couplings. Moreover, the axion of the model constitutes a viable dark matter candidate and neutrino masses are incorporated via the standard type-I seesaw mechanism. A simple extension of the model allows for Dirac neutrinos.
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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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Cheng, L., Eberhardt, O., & Murphy, C. W. (2019). Novel theoretical constraints for color-octet scalar models. Chin. Phys. C, 43(9), 093101–11pp.
Abstract: We study the theoretical constraints on a model whose scalar sector contains one color octet and one or two color singlet SU(2)(L) doublets. To ensure unitarity of the theory, we constrain the parameters of the scalar potential for the first time at the next-to-leading order in perturbation theory. Moreover, we derive new conditions guaranteeing the stability of the potential. We employ the HEPfit package to extract viable parameter regions at the electroweak scale and test the stability of the renormalization group evolution up to the multi-TeV region. Furthermore, we set upper limits on the scalar mass splittings. All results are given for both cases with and without a second scalar color singlet.
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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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