Precise measurements of SM particles properties at the LHC allows to look for heavy New Physics in the context of an Effective Field Theory (EFT). These searches, however, often rely on kinematic regions where the validity of the EFT may be compromised. In this paper we propose to address this issue by comparing with benchmark models. The connection between models and their manifestations as EFTs at low energies allows us to quantify the breakdown of the EFT, and describe ways to combine different sources of constraints beyond Higgs physics. To illustrate these techniques, in this paper we propose a set of benchmark models based on extensions of the Higgs sector, namely the inclusion of a singlet, a dilaton and generic 2HDMs. We obtain the matching between these models and the EFT involving the Higgs, electroweak bosons and fermions. We then describe current and future indirect and direct constraints, consider the effect of correlations among the coefficients within models, and discuss the validity of the EFT.
In this thesis, we discuss theoretical properties of various Higgs sectors, and we analyze constraints from current experimental data, and then we study collider signatures in each Higgs sector. In Part I, we focus on the phenomenology of various extended Higgs sectors such as the two Higgs doublet model, the Higgs triplet model and Higgs sectors in supersymmetric standard models. In Part II, we discuss new physics models at the TeV scale, in which the Higgs sector is extended, and neutrino masses, dark matter and/or baryon asymmetry of the Universe can be explained.
Properties of the Higgs sector of Two Higgs Doublet Model (2HDM) and existing constraints on its parameters are discussed. Potential of the Photon Linear Collider in testing various Higgs scenarios of 2HDM, including the MSSM, based on the realistic simulations is also presented.
The discovery of the Higgs boson like particle with the mass of around 126 GeV has given us a great clue to know what is the true Higgs sector. New physics models at the TeV scale often introduce Higgs sectors extended from the minimal form, so that the determination of the Higgs sector can be a probe of new physics models. In this talk, we focus on the Higgs sector with exotic representation fields whose isospin is larger than 1/2. We first discuss the general features of exotic Higgs sectors, and then we consider several concrete models to clarify them. The phenomenology of the Higgs triplet…
We demonstrate how CP violation manifests itself in the Higgs sector of the minimal supersymmetric extension of the Standard Model (MSSM). Starting with a brief introduction to CP violation in the MSSM and its effects on the Higgs sector, we discuss some phenomenological aspects of the Higgs sector CP violation based on the two scenarios called CPX and Trimixing
We introduce the public computer code HiggsSignals, which can be used to test the predictions from models with arbitrary Higgs sectors against experimental measurements. Following a brief description of the code, several examples of HiggsSignals applications are given. We derive constraints on extended Higgs sectors taking into account the measured rates for the observed LHC Higgs signal in all available channels. The results are presented both in a model-independent framework with coupling scale factors that parametrize deviations from the Standard Model, and in a model-dependent example wher…
The Next-to-Minimal Supersymmetric Standard Model (NMSSM) includes a Higgs iso-singlet superfield in addition to the two Higgs doublet superfields of the minimal supersymmetric extension. The Higgs sector and neutralino sectors of this model are examined within the context of a future linear collider.
I give a brief overview of the motivations for and experimental probes of extended Higgs sectors containing more than the single Higgs doublet field of the Standard Model.
Taking the most general two-doublet models with explicit CP violation in the Higgs sector but no phase in the CKM matrix, we determine the correlation between the Higgs and Kaon sectors using the experimental values of $ΔM_K$ and $ε_K$. It is found that: there is a direct correlation between strength of FCNC couplings and the Higgs masses, and the lightest Higgs is nearly pure CP-even, but this small CP-odd composition gives large enough contribution to $ε_K$.
We update our analysis of the Higgs sector masses in Minimal Supersymmetry and in the Two-Higgs Doublet Model to the final ATLAS and CMS data from the 2011-2012 LHC run.
We briefly review the phenomenological implications of the minimal supersymmetric standard model (MSSM) with explicit radiative breaking of CP invariance in the Higgs sector for the LEP2 and Tevatron colliders.
We construct a model of an unparticle sector consisting of a supersymmetric SU(N) gauge theory with the number of flavors in the Seiberg conformal window. We couple this sector to the MSSM via heavy messengers. The resulting low energy theory has a Higgs coupling to unparticles. The Higgs vev drives the hidden Seiberg sector to a new conformal fixed point. The coupling to the Higgs mediates supersymmetry breaking to the Seiberg sector, and breaks conformal invariance at a lower scale. The low energy theory contains light stable and metastable mesons. Higgs decay into this sector gives signatur…
We study the Higgs potential of the next-to-minimal renormalizable SUSY SO(10) GUT with 120 Higgs representation on top of the "standard" minimal model Higgs sector spanning over 10, 126bar+126 and 210. All the GUT-scale Higgs sector mass matrices for the 592 Higgs states of the model are written down in detail with all the conventions fully specified. The consistency of the results is checked by the decoupling of 120 and independently by the analysis of the relevant Goldstone modes. The matching of the Yukawa sector sum-rules driving the matter fermion masses and mixing at the level of the ef…
In this review we demonstrate physics potential of a photon linear collider by studying the neutral Higgs-boson sector of the MSSM in which interesting CP-violating Higgs mixing could arise via radiative corrections.
We study coupling constants of the standard model like Higgs boson with the gauge bosons $hZZ$ and $hWW$ and fermions $hf\bar{f}$ in the general Higgs sector which contains higher isospin representations with arbitrary hypercharge. In Higgs sectors with exotic Higgs representations, the $hZZ$ and $hWW$ coupling constants can be larger than those in the standard model. We calculate deviations in the Higgs boson couplings from standard model values in the model with a real or complex triplet field, the Georgi-Machacek model and the model with a septet scalar field. We also study deviations in th…
The theoretical structure of the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) is briefly described. An outline of Higgs phenomenology at future lepton colliders is presented, and some opportunities for probing the physics of the MSSM Higgs sector at an e-e- collider are considered.
Using the classical argument about tree level unitarity breakdown in combination with the precision electroweak data, it is shown, that if part of the Higgs sector is strongly interacting, this part is small and is out of range of the LHC.
We study the little hierarchy between mass parameters in the Higgs sector and other SUSY breaking masses. This type of spectrum can relieve the fine-tuning problem in the MSSM Higgs sector. Our scenario can be realized by superconformal dynamics. The spectrum in our scenario has significant implications in other phenomenological aspects like the relic abundance of the lightest neutralino and relaxation of the unbounded-from-below constraints.
HiggsBounds is a computer code which tests the Higgs sectors of new models against the current exclusion bounds from the Higgs searches at LEP and the Tevatron. As input, it requires a selection of model predictions, such as Higgs masses, branching ratios, effective couplings and total decay widths. HiggsBounds then uses the expected and observed topological cross section limits from the Higgs searches to determine which points in the parameter space have already been excluded at 95% CL. HiggsBounds will be updated to include new results as they become available.
Conditions for spontaneous Charge-Parity (CP) violation in the scalar potential sector of general $S(3)$ Higgs-doublet model (3HDM) are analyzed. An analysis of the Higgs sector of the minimal $S(3)$-invariant extension of the Standard Model including CP violation arising from the spontaneous breaking of the electroweak symmetry is presented. This extended Higgs sector with three SU(2) doublets Higgs fields with complex vev's provides an interesting scenario to analyze the Higgs masses spectrum, trilinear self-couplings and CP violation. We present how the spontaneous electroweak symmetry brea…
We present a comprehensive analysis on the MSSM Higgs sector CP violation at photon colliders including the chargino contributions as well as the contributions of other charged particles. The chargino loop contributions can be important for the would-be CP odd Higgs production at photon colliders. Polarization asymmetries are indispensable in determining the CP properties of neutral Higgs bosons.
The Higgs sector of the Standard Model and of the Two Higgs Doublet Extensions of SM, MSSM and the general 2HDM, can be tested in processes involving photons. A short review of the corresponding results is presented.
The mass and the decay width of a Higgs boson in the minimal standard model are evaluated by a variational method in the limit of strong self-coupling interaction. The non-perturbative technique provides an interpolation scheme between strong-coupling regime and weak-coupling limit where the standard perturbative results are recovered. In the strong-coupling limit the physical mass and the decay width of the Higgs boson are found to be very small as a consequence of mass renormalization. Thus it is argued that the eventual detection of a light Higgs boson would not rule out the existence of a …
We study the impact of the CP violation of the extra Higgs sector on $D^0$ decay. The CP even and CP odd neutral Higgs mixing of the two Higgs doublet model is studied and we show how the CP violating effect of the mixing may lead to the longitudinal muon polarization asymmetry of $D^0 \to μ^+ μ^-$. The asymmetry of the short-distance contribution is sensitive to the CP violating phase of the extended Higgs sector.
We explore the collider signatures of the Higgs sectors in singlet-extended MSSM models. We find that even with reduced couplings due to singlet mixing, a significant portion of the parameter spaces have a discoverable Higgs via traditional decay modes or via invisible decays (directly to neutralinos or through cascade decays to neutralinos and neutrinos). For illustrative points in parameter space we give the likelihood of Higgs discovery. In cases where neither traditional nor invisible modes can discover the Higgs, the neutralino sector may provide evidence for the extended models.
Higgs boson mass sum rules of supersymmetric models offer attractive targets for precision tests at future muon colliders. These sum rules involve the gauge boson masses as well as the masses of the Higgs boson states which can be precisely measured in the $s$-channel production process at a muon collider. These measurements can sensitively probe radiative corrections to the Higgs boson masses as well as test for CP-violation and nonminimality of the Higgs sector.
We review the potential of the LHC to detect a very light CP-odd Higgs boson of the NMSSM, $a_1$, through its direct production in association with a bottom-quark pair at large tan$β$. We also review the LHC discovery potential of the two lightest CP-even Higgs states, decaying into two lighter Higgs states or into the lightest CP-odd Higgs state and the $Z$ gauge boson.
CP-violating effects in the Higgs sector of the Minimal Supersymmetric Standard Model with complex parameters (cMSSM) are induced by potentially large higher-order corrections. As a consequence, all three neutral Higgs bosons can mix with each other. Recent results for loop corrections in the Higgs sector of the cMSSM are reviewed. Results for propagator-type corrections of O(alpha_t alpha_s) and complete one-loop results for Higgs cascade decays of the kind h_a -> h_b h_c are summarised, and the proper treatment of external Higgs bosons in Higgs-boson production and decay processes is discuss…
The study of charge asymmetry of W bosons in the process \egam\to eWW can be a tool for discovery of strong interaction in Higgs sector at energies that are lower than it is necessary for observation of resonances caused by this strong interaction.
A scalar sector of the 3 3 1 model with three Higgs triplets is considered. The mass spectrum, eigenstates and interactions of the Higgs and the SM gauge bosons are derived. We show that one of the neutral scalars can be identified with the standard model Higgs boson, and in the considered potential there is no mixing between scalars having VEV and ones without VEV.
Directly measuring the Higgs self-coupling is of great importance for testing the Brout-Englert-Higgs mechanism in the Standard Model. As a scattering that contains the direct information from the Higgs self-coupling, we investigate the process $μ^-μ^+\rightarrow HH$ in the threshold region. We calculate the one-loop corrections to the cross section and consider the non-perturbative contribution from the Higgs self-interactions in the final state. It is found that the scattering in the nonrelativistic domain could be an especial process to testing the Higgs sector directly.
We study implications of two dark matter candidate events at CDMS-II on the neutralino dark matter scenario in the supersymmetric standard model, in light of the recent lattice simulation on the strange quark content of a nucleon. The scattering rate of neutralino-nucleon is dominated by Higgs exchange processes and the mass of heavy Higgs boson is predicted for the neutralino of Bino-Higgsino mixing state. In the case of Wino-Higgsino mixing, the Higgs sector may not be constrained.
Little experimental data bears on the question of whether there is a spontaneously broken hidden sector that has no Standard Model quantum numbers. Here we discuss the prospects of finding evidence for such a hidden sector through renormalizable interactions of the Standard Model Higgs boson with a Higgs boson of the hidden sector. We find that the lightest Higgs boson in this scenario has smaller rates in standard detection channels, and it can have a sizeable invisible final state branching fraction. Details of the hidden sector determine whether the overall width of the lightest state is sm…
Some possibilities to test the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) at the LHC and future $e^+e^-$ colliders are discussed. This includes precision coupling strength measurements, the search for additional Higgs bosons as well as their decay to supersymmetric particles.
Testable Higgs partners may be sought within the extensions of the SM Higgs sector aimed at generating neutrino masses at the loop level. We study a viability of extended Higgs sectors for two selected models of radiative neutrino masses: a one-loop mass model, providing the Higgs partner within a real triplet scalar representation, and a three-loop mass model, providing it within its two-Higgs-doublet sector. The Higgs sector in the one-loop model may remain stable and perturbative up to the Planck scale, whereas the three-loop model calls for a UV completion around 106 GeV. Additional vector…
One Higgs was found. Are there more? In this work we discuss simple extension of the scalar sector of the Standard Model (SM) used as benchmark models by ATLAS and CMS in the searches for new scalars at the LHC. We discuss how much the discovered 125 GeV Higgs at the LHC resembles the SM Higgs and how will our understanding of the Higgs nature improve at future electron-positron colliders. Models with extended Higgs sectors provide very interesting scenarios, from the existence of charged Higgs bosons to CP-violating scalars that can be probed by the experimental collaborations at the LHC. Com…
In the decoupling limit of a non-minimal Higgs sector, the lightest CP-even Higgs boson (h) is indistinguishable from the Standard Model (SM) Higgs boson. In the two-Higgs-doublet sector of the MSSM, the approach to the decoupling limit (for m_A>>m_Z) persists, even in the presence of potentially large (tan(beta)-enhanced) radiative corrections to the hbb coupling. Radiative corrections can also generate an accidental cancellation between tree-level and one-loop terms, resulting in a SM-like Higgs boson for moderate m_A outside the decoupling regime.
Extended Higgs sectors appear in many models for physics beyond the Standard Model. Current Higgs measurements at the LHC are starting to significantly constrain them. We study their Higgs coupling patterns at tree level as well as including quantum corrections. Our benchmarks include a dark singlet-doublet extension and several two-doublet setups. Using SFitter we translate the current Higgs coupling measurements for one light Higgs state into their respective parameter spaces. Finally, we show how two-Higgs-doublet models can serve as a consistent ultraviolet completion of an assumed single …
We discuss a few new characteristic features of the loop-induced MSSM Higgs-sector CP violation at the LHC based on two scenarios: (i) CPX and (ii) Trimixing.
I review possible explanations of the muon g-2 anomaly in models with extended Higgs and matter sectors, focusing on extensions of the standard model and the two Higgs doublet model with vectorlike leptons. Predictions of these models, namely the modifications of muon Yukawa and gauge couplings, that can be searched for at the LHC and future colliders, are summarized. I also discuss striking predictions for di-Higgs and tri-Higgs signals at a muon collider that can be tested even at very low energies. Furthermore, I briefly comment on other interesting features and signatures of models with ex…
We study consequences of custodial symmetry in the Higgs sector of the Georgi-Machacek (GM) model. We discuss how the 5-plet and 3-plet Higgs bosons classified under the custodial SU(2) symmetry are produced and decay at the CERN Large Hadron Collider. By determining their masses through proposed channels, we can test the mass degeneracy in each Higgs multiplet.
We study the effect of explicit CP violation in the Higgs sectors of the MSSM in the di-photon decay of the lightest CP-mixed Higgs state. Further it is shown that the gluon fusion production mechanism along with the di-photon decay enhances CP-violating effects for a large set of suitably chosen parameter values.
We consider dark sectors with spontaneously broken gauge symmetries, where cascade decays of the dark sector fields naturally produce multi-Higgs boson final states along with dark matter. Our study focuses on two and three Higgs boson final states with missing energy using a multivariate analysis with Boosted Decision Trees. We find that the di-Higgs boson channel is quite promising for the $\bar b b + γγ$ and $\bar b b + \bar \ell \ell$ decay modes. The tri-Higgs boson final state with missing energy, on the other hand, appears to be beyond the reach of the LHC in analogous channels. This ma…
I present a general exclusion bound for the Higgs in fourth generation scenarios with a general lepton sector. Recent Higgs searches in fourth generation scenarios rule out the entire Higgs mass region between 120 and 600 GeV. That such a large range of Higgs masses are excluded is due to the presence of extra heavy flavors of quarks, which substantially increase Higgs production from gluon fusion over the Standard Model rate. However, if heavy fourth generation neutrinos are less than half of the Higgs mass, they can dominate the Higgs decay branching fraction, overtaking the standard Higgs t…
The LHC data implies that the newly discovered Higgs boson h may be sterile (highly SM-like). In supersymmetric SMs (SSMs), Higgs couplings are often modified by Higgs mixing and stop loop corrections, so we study the Higgs sterility in the Higgs and stop sectors in two SSMs: (I) The Minimal SSM (MSSM). In the nearly decoupling region, the doublet-doublet mixing effect can only enhance C_{hb\bar b} by 2m_Z^2/M_A^2. Sterility places M_A\gtrsim 900 GeV. But it hardly constrains the stop sector due to the heaviness of Higgs boson mass m_h; (II) The next to MSSM(NMSSM). In the presence of doublet-…
The CP structure of the Higgs sector will be of great interest to future colliders. The measurement of the CP properties of candidate Higgs particles will be essential in order to distinguish models of electroweak symmetry breaking, and to discover or place limits on CP-violation in the Higgs sector. In this report we briefly summarize various methods of determining the CP properties of Higgs bosons at different colliders and identify areas where more study is required. We also provide an example of a synergy between the LHC, an e+e- Linear Collider and a Photon Collider, for the examination o…
Here we study and compare the sensitivity to the Higgs sector of the SUSY-seesaw models via the LFV tau decays: tau-> 3 mu, tau->K^{+}K^{-}, tau->mu eta and tau-> mu f_{0}. We emphasize that, at present, the two later channels are the most efficient ones to test indirectly the Higgs particles.
We perform an exhaustive analysis of the most general Higgs sector of the minimal left-right symmetric model (MLRM). We find that the CP properties of the vacuum state are connected to the Higgs spectrum: if CP is broken spontaneously, the MLRM does not approach the Standard Model in the limit of a decoupling left-right symmetry breaking scale. Depending on the size of the CP phases scenarios with extra non-decoupling flavor-violating doublet Higgses or very light SU(2) triplet Higgses emerge, both of which are ruled out by phenomenology. For zero CP phases the non-standard Higgses decouple on…
We investigate the electroweak phase transition in the presence of a large CP violation in the squark sector of the MSSM. When the CP violation is large, scalar-pseudoscalar mixing of the Higgs bosons occurs and a large CP violation in the Higgs sector is induced. It, however, weakens first-order phase transition before the mixing reaches the maximal. Even when the CP violation in the squark sector is not so large that the phase transition is strongly first order, the phase difference between the broken and symmetric phase regions grows to O(1), which leads to successful baryogenesis, when the…
We discuss renormalization group equations (RGE) for the parameters of the Higgs sector in general Two-Higgs-Doublet Model (2HDM). We present the three-loop results but consider only contributions due to self-couplings of the Higgs doublets. We study the structure of RGE and express beta-functions in terms of reparametrization invariants with respect to higgs-basis rotations. The Cayley-Hamilton theorem is utilized to reduce both the number of independent tensor structures in matrix RGE and the number of invariants to a minimal set. As a by-product of our calculation we discovered that two-loo…
We consider an extended Higgs sector that arises as a low-energy description of a strongly-coupled SUSY gauge theory. This model predicts the presence of extra superfields that couple with the Higgs superfields through large coupling constants. Large radiative corrections involving the extra fields can realize strongly first order electroweak phase transition, which is a vital requirement for electroweak baryogenesis scenario. At the same time, the large radiative corrections lead to significant deviations in the Higgs boson triple coupling and Higgs-to-diphoton branching ratio, which are test…
In this paper, we review the role of a multi-TeV $e^+e^-$ linear collider to complete the mapping of the Higgs boson profile and studying heavier bosons in extended scenarios with more than one Higgs doublet.
