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Register a new userNew scenario for aligned Higgs couplings originated from the twisted custodial symmetry at high energies
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We investigate a new scenario of the two Higgs doublet model, where the current experimental data for the electroweak rho parameter and those for the Higgs boson couplings can be simultaneously explained. In this scenario, the two Higgs doublet model is supposed to be a low energy effective theory up to a high energy scale $Lambda$, above which a fundamental theory should appear. It is assumed that the Higgs potential respects a global symmetry at $Lambda$ (the twisted custodial symmetry), which is to be given as a consequence of the global symmetry structure of the fundamental theory above $Lambda$. By the analysis using one-loop renormalization group equations, the above experimental data can be explained in a natural way even when the masses of the extra Higgs bosons are near the electroweak scale. We also discuss the predictions on the mass spectrum of the additional Higgs bosons and also those on coupling constants of the standard-model-like Higgs boson, which make it possible to test this scenario at current and future collider experiments.
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We study the off-shell production of the Higgs boson at the LHC to probe Higgs physics at higher energy scales utilizing the process $g g rightarrow h^{*} rightarrow ZZ$. We focus on the energy scale dependence of the off-shell Higgs propagation, and of the top quark Yukawa coupling, $y_t (Q^2)$. Extending our recent study in arXiv:1710.02149, we first discuss threshold effects in the Higgs propagator due to the existence of new states, such as a gauge singlet scalar portal, and a possible continuum of states in a conformal limit, both of which would be difficult to discover in other traditional searches. We then examine the modification of $y_t (Q^2)$ from its Standard Model (SM) prediction in terms of the renormalization group running of the top Yukawa, which could be significant in the presence of large flat extra-dimensions. Finally, we explore possible strongly coupled new physics in the top-Higgs sector that can lead to the appearance of a non-local $Q^2$-dependent form factor in the effective top-Higgs vertex. We find that considerable deviations compared to the SM prediction in the invariant mass distribution of the $Z$-boson pair can be conceivable, and may be probed at a $2sigma$-level at the high-luminosity 14 TeV HL-LHC for a new physics scale up to $mathcal{O}(1 {~rm TeV})$, and at the upgraded 27 TeV HE-LHC for a scale up to $mathcal{O}(3 {~rm TeV})$. For a few favorable scenarios, $5sigma$-level observation may be possible at the HE-LHC for a scale of about $mathcal{O}(1 {~rm TeV})$.
We discuss the recent results on the muon anomalous magnetic moment in the context of new physics models with light scalars. We propose a model in which the one-loop contributions to g-2 of a scalar and a pseudoscalar naturally cancel in the massless limit due to the symmetry structure of the model. This model allows to interpolate between two possible interpretations. In the first interpretation, the results provide a strong evidence of the existence of new physics, dominated by the positive contribution of a CP-even scalar. In the second one, supported by the recent lattice result, the data provides a strong upper bound on new physics, specifically in the case of (negative) pseudoscalar contributions. We emphasize that tree-level signatures of the new degrees of freedom of the model are enhanced relative to conventional explanations of the discrepancy. As a result, this model can be tested in the near future with accelerator-based experiments and possibly also at the precision frontier.
We suggest that the exclusive Higgs + light (or b)-jet production at the LHC, $pp to h+j(j_b)$, is a rather sensitive probe of the light-quarks Yukawa couplings and of other forms of new physics (NP) in the Higgs-gluon $hgg$ and quark-gluon $qqg$ interactions. We study the Higgs $p_T$-distribution in $pp to h+j(j_b) to gamma gamma + j(j_b)$, i.e., in $h+j(j_b)$ production followed by the Higgs decay $h to gamma gamma$, employing the ($p_T$-dependent) signal strength formalism to probe various types of NP which are relevant to these processes and which we parameterize either as scaled Standard Model (SM) couplings (the kappa-framework) and/or through new higher dimensional effective operators (the SMEFT framework). We find that the exclusive $h+j(j_b)$ production at the 13 TeV LHC is sensitive to various NP scenarios, with typical scales ranging from a few TeV to ${cal O}(10)$ TeV, depending on the flavor, chirality and Lorentz structure of the underlying physics.
We calculate 1-loop radiative corrections to the $hZZ$ and $hWW$ couplings in models with next--to--simplest Higgs sectors satisfying the electroweak $rho$ parameter equal to 1 at tree level: the Higgs singlet model, the two-Higgs doublet models, and the Georgi-Machacek model. Under theoretical and current experimental constraints, the three models have different correlations between the deviations in the $hZZ$ and $hWW$ couplings from the standard model predictions. In particular, we find for each model predictions with no overlap with the other two models.
The $h(125)$ boson, discovered only in 2012, is lower than the top quark in mass, hence $t to ch$ search commenced immediately thereafter, with current limits at the per mille level and improving. As the $t to ch$ rate vanishes with the $h$-$H$ mixing angle $cosgamma to 0$, we briefly review the collider probes of the top changing $tcH/tcA$ coupling $rho_{tc}$ of the exotic $CP$-even/odd Higgs bosons $H/A$. Together with an extra top conserving $ttH/ttA$ coupling $rho_{tt}$, one has an enhanced $cbH^+$ coupling alongside the familiar $tbH^+$ coupling, where $H^+$ is the charged Higgs boson. The main processes we advocate are $cg to tH/A to ttbar c,; ttbar t$ (same-sign top and triple-top), and $cg to bH^+ to btbar b$. We also discuss some related processes such as $cg to thh$, $tZH$ that depend on $cosgamma$ being nonzero, comment briefly on $gg to H/A to tbar t, tbar c$ resonant production, and touch upon the $rho_{tu}$ coupling.
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