The minimal $U(1)_X$ extension of the Standard Model (SM) is a simple and well-motivated extension of the SM,
which supplements the SM with the seesaw mechanism for naturally generating the light neutrino masses
and offers various interesting phenomenologies. In the model, the $U(1)_X$ charge of each SM field is characterized
by the $U(1)_X$ charge of the SM Higgs doublet with a free parameter $x_H$. Due to the $U(1)_X$ charge of the Higgs doublet, the Higgs boson has a trilinear coupling
with the $Z$ boson and the $U(1)_X$ gauge boson ($Z^\prime$). With this coupling, a new process for the associated Higgs boson production
with a $Z$ boson arises through a $Z^\prime$ boson in the $s$-channel at high energy colliders. In this paper, we calculate the associated Higgs boson production at high energy colliders
and show interesting effects of the new $Z^\prime$ boson mediated process,
which can be tested in the future.
The presence of charged Higgs bosons is a generic prediction of multiplet extensions of the Standard Model (SM) Higgs sector. Focusing on the Two-Higgs-Doublet-Model (2HDM), we discuss the charged Higgs boson collider phenomenology in the theoretically and experimentally viable parameter space. While almost all existing experimental searches at the LHC target the fermionic decays of charged Higgs bosons, we point out that the bosonic decay channels -- especially the decay into a non-SM-like Higgs boson and a $W$ boson -- often dominate over the fermionic channels. Moreover, we revisit two genu…
Production in association with an electroweak vector boson V is a distinctive mode of production for a Higgs boson H without tree-level couplings to fermions, known as a fermiophobic Higgs boson. We focus on HV associated production with H decay into a pair of photons, and V into a pair of jets, with the goal of distinguishing a fermiophobic Higgs boson from the standard model Higgs boson. Performing a simulation of the signal and pertinent QCD backgrounds, and using the same event selection cuts employed by the LHC ATLAS Collaboration, we argue that existing LHC data at 7 TeV with 4.9 fb^{-1}…
The search for evidence of beyond Standard Model Higgs bosons is an integral part of the Higgs boson studies at the LHC. This article reviews recent beyond Standard Model Higgs boson searches using Run I LHC proton-proton collision data recorded by the ATLAS detector. In particular, searches for Higgs boson cascades, double Higgs boson production, scalar particles decaying to $γγ$ pairs, flavor changing neutral currents involving Higgs bosons, and Higgs bosons decaying to invisible particles are discussed. No significant deviations from the background expectations are found and corresponding c…
More than one Higgs boson may be present near the currently discovered Higgs mass, which can not be properly resolved due to the limitations in the intrinsic energy resolution at the Large Hadron Collider. We investigated the scenarios where two $CP$-even Higgs bosons are degenerate in mass. To correctly predict the Higgs signatures, quantum interference effects between the two Higgs bosons must be taken into account, which, however, has been often neglected in the literature. We carried out a global analysis including the interference effects for a variety of Higgs searching channels at the L…
The Monte Carlo integrator HAWK provides precision predictions for Higgs production at hadron colliders in vector-boson fusion and Higgs strahlung, i.e. in production processes where the Higgs boson is Attached to WeaK bosons. The fully differential predictions include the full QCD and electroweak next-to-leading-order corrections. Results are computed as integrated cross sections and as binned distributions for important hadron-collider observables.
The Higgs boson physics reach of the CMS detector with 300(0) fb-1 of proton-proton collisions at sqrt{s} = 14 TeV is presented. Precision measurements of the Higgs boson properties, Higgs boson pair production and self-coupling, rare Higgs boson decays, and the potential for additional Higgs bosons are discussed.
We review the search for the standard Higgs boson, the Higgs bosons of the supersymmetric standard model, and Higgs bosons from a variety of other models at present and future colliders.
We review possible properties of Higgs bosons in the NMSSM, which allow to discriminate this model from the MSSM: masses of mostly Standard-Model-like Higgs bosons at or above 140 GeV, or enhanced branching fractions into two photons, or Higgs-to-Higgs decays. In the case of a Standard-Model-like Higgs boson above 140 GeV, it is necessarily accompagnied by a lighter state with a large gauge singlet component. Examples for such scenarios are presented. Available studies on Higgs-to-Higgs decays are discussed according to the various Higgs production modes, light Higgs masses and decay channels.
Higgs Bosons produced via gluon-gluon fusion (ggF) with large transverse momentum ($p_T$) are sensitive probes of physics beyond the Standard Model. However, high $p_T$ Higgs Boson production is contaminated by a diversity of production modes other than ggF: vector boson fusion, production of a Higgs boson in association with a vector boson, and production of a Higgs boson with a top-quark pair. Combining jet substructure and event information with modern machine learning, we demonstrate the ability to focus on particular production modes. These tools hold great discovery potential for boosted…
In models with extended Higgs sector and additional matter fields, the decay modes of heavy Higgs bosons can be dominated by cascade decays through the new fermions rendering present search strategies ineffective. We investigate new decay topologies of heavy neutral Higgses in two Higgs doublet model with vectorlike leptons. We also discuss constraints from existing searches and discovery prospects. Among the most interesting signatures are monojet, mono Z, mono Higgs, and Z and Higgs bosons produced with a pair of charged leptons.
We interpret the potential observation of the 750 GeV di-photon resonance at the LHC in models, in which an $SU(2)$ isospin-singlet scalar boson mixes with the Standard Model (SM) Higgs boson through an angle $α$. Allowing the singlet scalar boson to have renormalizable couplings to vector-like leptons and quarks and introducing sizable decay width of the 750 GeV di-photon resonance into non-SM particles such as dark matters, we can explain the large production cross section $σ(H_2) \times B(H_2 \to γγ)$ as well as the apparent large total width of the boson without conflicts from the results …
Since the discovery of the Higgs boson in the year 2012, the CMS experiment continuously makes use of a variety of final states to measure the properties of the Higgs boson, as well as to search for it in final states where the discovery could not yet be established. This article concentrates on Higgs searches in fermionic final states including a search for the Standard Model Higgs boson in the $H \rightarrow b\overline{b}$ channel. Furthermore, three different searches for Higgs bosons beyond the Standard Model are presented. These comprise two searches for heavy neutral Higgs bosons and one…
We report results from searches for neutral Higgs bosons produced in p-pbar collisions recorded by the Dzero experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the tautau final state and in association with a b quark in the btautau and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are…
The ATLAS and CMS experiments have recently discovered a new 125 GeV scalar boson. We show that the properties of this scalar, including the enhancement of its diphoton decay rate, can be explained in a model with an isospin symmetric Higgs boson. The predictions of the model relevant for future experiments are also discussed.
In supersymmetric theories of nature the Higgsino fermionic superpartner of the Higgs boson can arise as the lightest standard model superpartner depending on the couplings between the Higgs and supersymmetry breaking sectors. In this letter the production and decay of Higgsino pairs to the Goldstone fermion of supersymmetry breaking and the Higgs boson, h, or gauge bosons, Z or $γ$ are considered. Relatively clean di-boson final states, hh, $h γ$, hZ, $Z γ$, or ZZ, with a large amount of missing energy result. The latter channels provide novel discovery modes for supersymmetry at high energy …
We identify two types of well-motivated, so-far experimentally unexplored LHC signatures of extended Higgs sectors: First, Higgs-to-Higgs decay signatures that involve (at least) two Beyond-the-Standard Model (BSM) neutral scalar bosons, $ϕ_i \to ϕ_j ϕ_k$. These signatures are discussed in the framework of the Two-Real-Singlet-Model (TRSM), which can furthermore exhibit cascades of Higgs-to-Higgs decays leading to multi-Higgs final states. Second, the charged Higgs boson decay to a W boson and a neutral BSM Higgs boson, which can easily become the dominant decay within the Two-Higgs-Doublet-Mo…
We discuss the lightest Higgs boson mass in the minimal supersymmetric Standard Model with "pure gravity mediation". By requiring that the model provides the observed dark matter density, we find that the lightest Higgs boson is predicted to be below 132GeV. We also find that the upper limit on the lightest Higgs boson mass becomes 128GeV, if we further assume thermal leptogenesis mechanism as the origin of baryon asymmetry of universe. The interrelations between the Higgs boson mass and the gaugino masses are also discussed.
Recent results of searches for Higgs bosons by the CMS collaboration are presented. These consist of searches for rare Higgs boson decays, searches for additional neutral Higgs bosons, and searches for charged Higgs bosons.
We show that the standard model (SM)-like Higgs boson may decay into neutrinos with a sizable decay branching ratio in one well-known two Higgs doublet model, so-called neutrinophilic Higgs model. This could happen if the mass of the lighter extra neutral Higgs boson is smaller than one half of the SM-like Higgs boson mass. The definite prediction of this scenario is that the rate of the SM-like Higgs boson decay into diphoton normalized by the SM value is about 0.9. In the case that a neutrino is Majorana particle, a displaced vertex of right-handed neutrino decay would be additionally observ…
We show that, in the present inclusive searches for the Higgs boson at the LHC, a fermiophobic Higgs mimics the standard-model-like Higgs if its mass is around 125 GeV. For that mass the order-of-magnitude reduction of fermiophobic Higgs production cross sections is compensated by a corresponding increase in the Higgs branching fraction into $γγ$, while the $WW^*,$ $ZZ^*,$ $Zγ$ signal yields are predicted to be somewhat smaller. The excess seen in the ATLAS and CMS fermiophobic Higgs boson searches in $γγ$ channel, including the exclusive vector-boson-fusion analysis, suggests that the LHC see…
We compute the next-to-next-to-leading order QCD corrections to Higgs boson production in weak boson fusion followed by its decay to a $b\bar b$ pair or to a pair of leptonically-decaying $W$ bosons. Our calculation allows us to compute realistic fiducial cross sections and assess the impact of fiducial cuts applied to the Higgs boson decay products on the magnitude of QCD radiative corrections in weak boson fusion.
The existence of charged Higgs boson(s) is inevitable in models with two (or more) Higgs doublets. Hence, their discovery would constitute unambiguous evidence for new physics beyond the Standard Model (SM). Taking into account all relevant results from direct charged and neutral Higgs boson searches at LEP and the LHC, as well as the most recent constraints from flavour physics, we present a detailed analysis of the current phenomenological status of the charged Higgs sector in a variety of well-motivated Two Higgs Doublet Models (2HDMs). We find that charged Higgs bosons as light as 75 GeV c…
By using the LHC and Tevatron measurements of the cross sections to various decay channels relative to the standard model Higgs boson, the total width of the putative 125 GeV Higgs boson is determined as 6.1 +7.7-2.9 MeV. We describe a way to estimate the branching fraction for Higgs decay to dark matter. We also discuss a No-Go theorem for the gammagamma signal of the Higgs boson at the LHC.
We propose a novel process where singly charged Higgs bosons are produced in a same-sign pair via vector boson fusion at hadron colliders in two Higgs doublet models. The process directly relates to the global symmetry structure of the Higgs potential. The produced charged Higgs bosons predominantly decay into a tau lepton and the neutrino or into a pair of top and bottom quarks, depending on the type of Yukawa interactions. We evaluate the signal and the background for the both cases at the CERN Large Hadron Collider and future higher-energy hadron colliders. We find that the process can be f…
We propose a new method to determine the spin of Higgs bosons at the LHC by using the decay products of black holes. Black holes may be produced if TeV-scale gravity theories are correct, and black holes decay into several particles. This decay results in the emission of high energy particles, including Higgs bosons. The difference of the degree of freedom between spin 0 and spin 1 Higgs bosons leads to a difference of the number of reconstructed Higgs bosons. From this fact, we can determine the spin of Higgs bosons with $5 σ$ significance by using the integrated luminosity L = 2.4 fb^-1, whi…
Various theories beyond the Standard Model predict the existence of heavy resonances decaying to Higgs (H) boson pairs. In order to maximize the sensitivity of searches for such resonances, it is important that experimental analyses cover a variety of decay modes. The decay of H boson pairs to four $τ$ leptons (HH$ \to ττττ$) has not been discussed in the literature so far. This decay mode provides a small branching fraction, but also comparatively low backgrounds. We present an algorithm for the reconstruction of the mass of the H boson pair in events in which the H boson pair decays via HH$ …
Searches for diphoton resonance have been shown to be very useful in discovering new heavy spin-0 or spin-2 particles. Supposing that a new heavy particle shows up in the diphoton channel and it points to a spin-0 boson, it can be allowed to have a small mixing with the observed 125 GeV Higgs-like boson. We borrow the example of the 750 GeV particles hinted with 3.2 fb$^{-1}$ data at the end of 2015 (though it did not appear in the 2016 data) to perform an analysis of "double Higgcision". In this work, we perform a complete Higgs-signal strength analysis in the Higgs-portal type framework, usi…
The present status of ATLAS searches for Higgs bosons in extensions of the Standard Model (SM) is presented. This includes searches for the Higgs bosons of the Two-Higgs-Doublet Model (2HDM), the Minimal Supersymmetric Model (MSSM), the Next-to-Minimal Supersymmetric Model (NMSSM) and models with an invisibly decaying Higgs boson. A review of the phenomenology of the Higgs sectors of these models is given together with the search strategy and the resulting experimental constraints.
We calculate the multi-photon decay widths of the Higgs boson from an effective Lagrangian for a system of electromagnetic and Higgs fields. We utilize a low-energy theorem to connect the above Lagrangian to the Heisenberg-Euler effective Lagrangian induced by charged particles that gain mass from interactions with the Higgs boson. In the standard model only the W^\pm gauge bosons and the top quark are relevant, and we compute their contributions to the effective couplings and the multi-photon decay widths of the Higgs boson.
The scenario of two mass-degenerate Higgs bosons within the general two-Higgs-doublet model (2HDM) is revisited. We focus on the global picture when two $CP$-even Higgs bosons of $h$ and $H$ are nearly mass-degenerate. A global fit to the signal strength of the 125 GeV Higgs measured at the LHC is performed. Based on the best-fit result of the 2HDM mixing angles $(α,β)$, theoretical constraints, charged and $CP$-odd Higgs boson direct search constraints and the electroweak precision constraints are imposed to the 2HDM parameter space. We present the signal predictions of the $(4b\,, 2b\,2γ)$ c…
Charged Higgs boson can exist in many physics beyond the standard models (BSM) and it is the obvious BSM signal. We briefly describe why the 125GeV scalar discovered at the LHC must have (heavy) companion: the charged Higgs boson, in a new paradigm. We then focus on the charged Higgs phenomenology, especially on how to measure $\tanβ$ precisely utilizing the top quark polarization information.
We explore the implications of a 126 GeV Higgs boson indicated by the recent LHC results for two-Higgs doublet model (2HDM). Identifying the 126 GeV Higgs boson as either the lighter or heavier of CP even neutral Higgs bosons in 2HDM, we examine how the masses of Higgs fields and mixing parameters can be constrained by the theoretical conditions and experimental constraints. The theoretical conditions taken into account are the vacuum stability, perturbativity and unitarity required to be satisfied up to a cut-off scale. We also show how bounds on the masses of Higgs bosons and mixing paramete…
We present an algorithm for the reconstruction of the Higgs mass in events with Higgs bosons decaying into a pair of tau leptons. The algorithm is based on matrix element (ME) techniques and achieves a relative resolution on the Higgs boson mass of typically 15-20%. A previous version of the algorithm has been used in analyses of Higgs boson production performed by the CMS collaboration during LHC Run 1. The algorithm is described in detail and its performance on simulated events is assessed. The development of techniques to handle tau decays in the ME formalism represents an important result …
In the MSSM weak boson fusion produces the two CP even Higgs bosons with a combined strength equivalent to the production of the Standard Model Higgs boson. The tau tau decay mode --- supplemented by gamma gamma --- provides a highly significant signal for at least one of the CP even Higgs bosons at the LHC with reasonable luminosity. The accessible parameter space covers the entire physical range which will be left unexplored by LEP2.
We investigate the potential for measuring the relative couplings of a low-mass Higgs boson at the Large Hadron Collider using WH, ZH, and ttbarH production, where the Higgs boson decays to tau-lepton pairs. With 100/fb of sqrt(s) = 14 TeV pp collision data we find that these modes can improve sensitivity to coupling-ratio measurements of a Higgs boson with a mass of about 125 GeV/c^2.
We study the Higgs boson decays and production via gluon fusion at the LHC as a probe of two typical littlest Higgs models which introduce a top quark partner with different (even and odd) T-parity to cancel the Higgs mass quadratic divergence contributed by the top quark. For each model we consider two different choices for the down-type quark Yukawa couplings. We first examine the branching ratios of the Higgs boson decays and then study the production via gluon fusion followed by the decay into two photons or two weak gauge bosons. We find that the predictions can be quite different for dif…
We study the possibility to separate in gluon fusion loop-induced Higgs boson production from point-like production. The Higgs boson is reconstructed in the Hgg final state at very large transverse momentum. Using the Higgs boson yields (normalized to the overall rate) and the shape of the Higgs boson pt distribution the two hypotheses can be separated with 2 standard deviations with an integrated luminosity of about 500 fb^-1. The largest experimental uncertainty affecting this estimate is the background event yield. The theoretical uncertainties from missing top mass effects are large, but c…
Pseudoscalar and charged Higgs bosons production in the processes $μ^+ μ^-\to P^0_i Z^0$, $μ^+μ^- \to H^{\pm}W^{\mp}$ within the models with several Higgs doublets and singlets is considered.
Theoretical overview on phenomenology of Higgs boson and SUSY Higgs boson at a future linear collider experiment is given as a Higgs and SUSY Higgs working group summary report for LCWS 2000.
We explore the possibility of distinguishing the SM-like MSSM Higgs boson from the SM Higgs boson via Higgs boson pair production at future muon collider. We study the behavior of the production cross section in SM and MSSM with Higgs boson mass for various choices of MSSM parameters tan βand m\sub A. We observe that at fixed CM energy, in the SM, the total cross section increases with the increase in Higgs boson mass whereas this trend is reversed for the MSSM case. The changes that occur for the MSSM case in comparison to the SM predictions are quantified in terms of the relative percentage …
We discuss the triviality and spontaneous symmetry breaking scenario where the Higgs boson without self-interaction coexists with spontaneous symmetry breaking. We argue that non perturbative lattice investigations support this scenario. Moreover, from lattice simulations we predict that the Higgs boson is rather heavy. We estimate the Higgs boson mass $m_H = 754 \pm 20 {\text{(stat)}} \pm 20 {\text{(syst)}} {\text{GeV}}$ and the Higgs total width $Γ(H) \simeq 340 {\text{GeV}}$.
The influence of the QCD structure of the weak bosons on the Higgs boson production in $e$-$p$ scattering is studied. The energy and Higgs boson mass dependence of the cross-section, following from the new contributions, is calculated.
Compared with the MSSM or the NMSSM with a low λ, λ-SUSY theory with a large λaround one has been deemed as a most natural realization of NMSSM. In this work, we treat the next-to-lightest CP-even Higgs boson as the SM-like Higgs boson in λ-SUSY and study the properties of the Higgs bosons and the pair production of the SM-like Higgs boson by considering various experiment constraints. We find that naturalness plays an important role in selecting the parameter space of λ-SUSY. In the most natural region of parameter space, the triple self coupling of the SM-like Higgs boson compared with its S…
The left-right twin Higgs(LRTH) model predicts the existence of three additional Higgs bosons: one neutral Higgs $ϕ^{0}$ and a pair of charged Higgs bosons $ϕ^{\pm}$. In this paper, we studied the production of a pair of charged and neutral Higgs bosons associated with standard model gauge boson $Z$ at the ILC, i.e., $e^{+}e^{-}\rightarrow Zϕ^{+}ϕ^{-}$ and $e^{+}e^{-}\rightarrow Zϕ^{0}ϕ^{0}$. We calculate the production rate and present the distributions of the various observables, such as, the distributions of the energy and the transverse momenta of final $Z$-boson and charged Higgs boson $ϕ…
Searches for charged Higgs bosons are an integral part of current and future investigations at the LHC. The LHC Higgs Cross Section Working Group (LHCHXSWG) was created to provide cross sections, branching ratios, analysis strategies etc. for Higgs boson searches at the LHC. We briefly review progress and results for charged Higgs bosons in and for the LHCHXSWG.
The total cross section for Higgs boson production via the dominant gluon fusion mechanism including NLO [two-loop] QCD corrections can be calculated numerically with the program HIGLU. The QCD corrections are included for arbitrary Higgs and quark masses and increase the cross section at the LHC by up to a factor of 2. The source code HIGLU provides the evaluation of the production of the Standard Model [SM] Higgs boson as well as the neutral Higgs bosons of the minimal supersymmetric extension [MSSM]. The program HDECAY determines the decay widths and branching ratios of the Higgs bosons wit…
We consider the two-Higgs-doublet model with explicit CP-violation, where the effective Higgs potential is not CP-invariant at the tree-level. Three neutral Higgs bosons of the model are the mixtures of CP-even and CP-odd bosons which exist in the CP-conserving limit of the theory. The mass spectrum and tree-level couplings of the neutral Higgs bosons to gauge bosons and fermions are significantly dependent on the parameters of the Higgs boson mixing matrix. We calculate the Higgs-gauge boson, Higgs-fermion, triple and quartic Higgs self-interactions in the MSSM with explicit CP-violation in t…
In the case of minimal supersymmetric extension of the Standard Model (MSSM), when the pseudoscalar Higgs boson mass is less than the supersymmetry energy scale, the effective theory at the electroweak scale is a two-Higgs-doublet model. We diagonalize the mass matrix of the general two-Higgs-doublet model, expressing Higgs boson self-couplings in terms of two mixing angles and four Higgs boson masses, and derive in a compact form the complete set of Feynman rules, including quartic couplings in the Higgs sector, for the case of CP-violating potential. Some processes of double and triple Higgs…
We study an upper bound on masses of additional scalar bosons from the electroweak precision data and theoretical constraints such as perturbative unitarity and vacuum stability in the two Higgs doublet model taking account of recent Higgs boson search results. If the mass of the Standard-Model-like Higgs boson is rather heavy and is outside the allowed region by the electroweak precision data, such a discrepancy should be compensated by contributions from the additional scalar bosons. We show the upper bound on masses of the additional scalar bosons to be about 2 $(1)$ TeV for the mass of the…
We consider the triple coupling of the Higgs boson in the context of the gauge-Higgs unification scenario. We show that the triple coupling of the Higgs boson in this scenario generically deviates from SM prediction since the Higgs potential in this scenario has a periodicity. We calculate the coupling in the five-dimensional $SU(3)$ x $U(1)_X$ gauge-Higgs unification model and obtain 70% deviation from the SM prediction.
We explain the current excess seen at the Large Hadron Collider via the $gg\to H\toγγ$ channel in the search for a neutral Higgs boson in terms of both singly (marginally) and doubly (predominantly) charged Higgs bosons predicted by the Higgs Triplet Model.
We show that it is possible to construct models in which the width of the Higgs boson is arbitrary - either smaller or larger than a standard model Higgs boson of the same mass. There are no new fields into which the Higgs boson decays. Instead, the coupling of the Higgs boson to the gauge bosons is adjusted. We construct and analyze weakly--coupled models with arbitrary--width Higgs bosons to investigate the phenomenology one might find in a strongly interacting model. In any such model new physics must enter at a mass scale which decreases as the Higgs boson width is adjusted away from its s…
We consider the measurement of the trilinear couplings of the neutral Higgs bosons in the Minimal Supersymmetric Standard Model~(MSSM) at a high energy $e^+ e^-$ linear collider in the light of the discovery of a Higgs boson at the CERN Large Hadron Collider~(LHC). We identify the state observed at the LHC with the lightest Higgs boson~($h^0$) of the MSSM, and impose the constraints following from this identification, as well as other experimental constraints on the MSSM parameter space. In order to measure trilinear neutral Higgs couplings, we consider different processes where the heavier Hi…
