A bstractAnomalous couplings of the Z boson to top quarks are only marginally constrained by direct searches and are still sensitive to new particle dynamics at the TeV scale. Employing an effective field theory approach we consider the dimension-six operators which generate deviations from the standard-model vector and axial-vector interactions. We show that rare B and K meson decays together with electroweak precision observables provide strong constraints on these couplings. We also consider constraints from t-channel single-top production.

We study the LHC phenomenology of flavor changing Yukawa couplings between the top quark, the Higgs boson, and either an up or charm quark. Such tuh or tch couplings arise for instance in models in which the Higgs sector is extended by the existence of additional Higgs bosons or by higher dimensional operators. We emphasize the importance of anomalous single top plus Higgs production in these scenarios, in addition to the more widely studied t → hj decays. By recasting existing CMS searches in multilepton and diphoton plus lepton final states, we show that bounds on ℬ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{\mathcal{B}} $$\end{document}(t → hu) are improved by a factor of 1.5 when single top plus Higgs production is accounted for. We also recast the CMS search for vector boson plus Higgs production into new, competitive constraints on tuh and tch couplings, setting the limits of ℬ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{\mathcal{B}} $$\end{document}(t → hu) < 0.7% and ℬ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{\mathcal{B}} $$\end{document}(t → hc) < 1.2%. We then investigate the sensitivity of future searches in the multilepton channel and in the fully hadronic channel. In multilepton searches, studying the lepton rapidity distributions and charge assignments can be used to discriminate between tuh couplings, for which anomalous single top production is relevant, and tch couplings, for which it is suppressed by the parton distribution function of the charm quark. An analysis of fully hadronic t + h production and t → hj decay can be competitive with the multilepton search at 100 fb−1 of 13 TeV data if jet substructure techniques are employed to reconstruct boosted top quarks and Higgs bosons. To show this we develop a modified version of the HEPTopTagger algorithm, optimized for tagging t → hj decays. Our sensitivity estimates on ℬ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{\mathcal{B}} $$\end{document}(t → hu) (ℬ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{\mathcal{B}} $$\end{document}(t → hc)) at 100 fb−1 of 13 TeV data for multilepton searches, vector boson plus Higgs search and fully hadronic search are 0.22% (0.33%), 0.15% (0.19%) and 0.36% (0.48%), respectively.

We study implications of large lepton-quark-leptoquark couplings for direct leptoquark searches at Large Hadron Collider. We present all existing flavor constraints on the strength of these couplings assuming that leptoquarks under consideration interact exclusively with charged leptons and quarks of the same generation. We find that these leptoquarks can have sizeable couplings to the Standard Model fermions. This insures a self consistency of our study. We discuss the leptoquark production mechanisms at LHC and demonstrate the importance of inclusion of a t-channel pair production and, in particular, a single leptoquark production through a recast of an existing CMS search at LHC for the second generation leptoquark. Our recast yields the best direct limit on Yukawa coupling of the second generation leptoquark that couples to a muon and a strange quark to date.

A bstractWe study the LHC phenomenology of flavor changing Yukawa couplings between the top quark, the Higgs boson, and either an up or charm quark. Such tuh or tch couplings arise for instance in models in which the Higgs sector is extended by the existence of additional Higgs bosons or by higher dimensional operators. We emphasize the importance of anomalous single top plus Higgs production in these scenarios, in addition to the more widely studied t → hj decays. By recasting existing CMS searches in multilepton and diphoton plus lepton final states, we show that bounds on ℬ$$ \mathrm{\mathcal{B}} $$(t → hu) are improved by a factor of 1.5 when single top plus Higgs production is accounted for. We also recast the CMS search for vector boson plus Higgs production into new, competitive constraints on tuh and tch couplings, setting the limits of ℬ$$ \mathrm{\mathcal{B}} $$(t → hu) < 0.7% and ℬ$$ \mathrm{\mathcal{B}} $$(t → hc) < 1.2%.We then investigate the sensitivity of future searches in the multilepton channel and in the fully hadronic channel. In multilepton searches, studying the lepton rapidity distributions and charge assignments can be used to discriminate between tuh couplings, for which anomalous single top production is relevant, and tch couplings, for which it is suppressed by the parton distribution function of the charm quark. An analysis of fully hadronic t + h production and t → hj decay can be competitive with the multilepton search at 100 fb−1 of 13 TeV data if jet substructure techniques are employed to reconstruct boosted top quarks and Higgs bosons. To show this we develop a modified version of the HEPTopTagger algorithm, optimized for tagging t → hj decays. Our sensitivity estimates on ℬ$$ \mathrm{\mathcal{B}} $$(t → hu) (ℬ$$ \mathrm{\mathcal{B}} $$(t → hc)) at 100 fb−1 of 13 TeV data for multilepton searches, vector boson plus Higgs search and fully hadronic search are 0.22% (0.33%), 0.15% (0.19%) and 0.36% (0.48%), respectively.

We perform an analysis of Higgs portal models of dark matter (DM), where DM is light enough to contribute to invisible Higgs decays. Using effective field theory we show that DM can be a thermal relic only if there are additional light particles present with masses below a few 100 GeV. We give three concrete examples of viable Higgs portal models of light DM: (i) the SM extended by DM scalar along with an electroweak triplet and a singlet, (ii) a Two Higgs Doublet Model of type II with additional scalar DM, (iii) SM with DM and an extra scalar singlet that is lighter than DM. In all three examples the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$ \mathcal{B} $\end{document}(h → invisible) constraint is not too restrictive, because it is governed by different parameters than the relic abundance. Additional light particles can have implications for flavor violation and collider searches.

A bstractWe perform an analysis of Higgs portal models of dark matter (DM), where DM is light enough to contribute to invisible Higgs decays. Using effective field theory we show that DM can be a thermal relic only if there are additional light particles present with masses below a few 100 GeV. We give three concrete examples of viable Higgs portal models of light DM: (i) the SM extended by DM scalar along with an electroweak triplet and a singlet, (ii) a Two Higgs Doublet Model of type II with additional scalar DM, (iii) SM with DM and an extra scalar singlet that is lighter than DM. In all three examples the $ \mathcal{B} $(h → invisible) constraint is not too restrictive, because it is governed by different parameters than the relic abundance. Additional light particles can have implications for flavor violation and collider searches.

A bstractLight vector-like quarks with non-renormalizable couplings to the Higgs are a common feature of models trying to address the electroweak (EW) hierarchy problem by treating the Higgs as a pseudo-goldstone boson of a global (approximate) symmetry. We systematically investigate the implications of the leading dimension five operators on Higgs phenomenology in presence of dynamical up- and down-type weak singlet as well as weak doublet vector-like quarks. After taking into account constraints from precision EW and flavour observables we show that contrary to the renormalizable models, significant modifications of Higgs properties are still possible and could shed light on the role of vector-like quarks in solutions to the EW hierarchy problem. We also briefly discuss implications of higher dimensional operators for direct vector-like quark searches at the LHC.

A bstractWe consider the impact of colored scalars that can couple directly to matter fields on the recently measured h → γγ excess. Among all possible candidates only scalar states transforming as (8, 2, 1/2) and ($ \overline{\mathbf{6}} $, 3, −1/3) under the Standard Model gauge group can individually accommodate the excess and remain in agreement with all available data. Current experimental constraints require such colored states to have an order one coupling to the Standard Model Higgs and a mass below 300 GeV. We use the best fit values to predict the correlated effect in h → Zγ and di-Higgs production. We furthermore discuss where and how these states appear in extensions of the Standard Model with primary focus on scenarios of matter unification. We revisit two simple SU(5) setups to show that these two full-fledged models not only accommodate a light color octet state but correlate its mass with observable partial proton decay lifetimes.