Higgs Boson Interactions Research Articles

Higgs-Boson Decay to Lepton Pair and Photon and Possible Non-Hermiticity of the Yukawa Interaction

The production of lepton pairs in the Higgs boson decay $h \to \ell^+ \ell^- \gamma$ is studied. The emphasis is put on the structure of the Higgs boson interaction with the fermions. This interaction is chosen as a mixture of the scalar and pseudo-scalar couplings, and, in addition, it is supposed to be non-Hermitian. We study prediction of this model for the observables in the $h \to \ell^+ \ell^- \gamma$ decay for the $e^+ e^-$, $\mu^+ \mu^-$ and $\tau^+ \tau^-$ pairs. The differential decay width and lepton forward-backward asymmetry are calculated as functions of the dilepton invariant mass for several sets of $h f \bar{f}$ coupling constants. The influence of non-Hermitian $h f \bar{f}$ interaction on the forward-backward asymmetry is studied, and large influence of a possible non-Hermiticity of the Higgs interaction with the top quarks on forward-backward asymmetry for $e^+ e^-$ and $\mu^+ \mu^-$ pairs is stressed.

Decay of the Higgs boson toτ−τ+and non-Hermiticy of the Yukawa interaction

The issue of Hermiticity of the Higgs boson interaction with fermions is addressed. A model for non-Hermitian Yukawa interaction is proposed and approximation of one fermion generation is considered. Symmetry properties of the corresponding $h f \bar{f}$ Lagrangian with respect to the discrete P, C and T transformations are analyzed, and the modified Dirac equation for the free fermion is studied. Longitudinal polarization of the fermions in the decay $h \to f \bar{f}$, which arises due to non-Hermiticity of the $h f \bar{f}$ interaction, is discussed. It is suggested to study effects of this non-Hermiticity in the decay $h \to \tau^- \tau^+ \to \mu^- {\bar \nu}_\mu \nu_\tau \, \mu^+ \nu_\mu {\bar \nu}_\tau$, for which observables (asymmetries) are constructed which take nonzero values for a non-Hermitian $h \tau^- \tau^+$ interaction. These asymmetries are analyzed for various configurations of the muon energies.

General analysis of the charged Higgs sector of theY=0triplet-singlet extension of the MSSM at the LHC

We investigate the extended Higgs sectors, specially the charged Higgs sector in a supersymmetric $Y=0$ $SU(2)$ triplet and a Standard Model (SM) gauge singlet extension of SM. We show that in this model the allowed data for the Higgs boson interaction eigenstates tend to group into separate blocks for $SU(2)$ triplet, doublet and singlet. The triplet sector has two degenerate paired states, each pair composed of a mostly-triplet charged Higgs and of a mostly-triplet scalar or pseudoscalar state. The mostly-doublet sector involves a Standard Model like Higgs of 125 GeV and extra mass-degenerate states, composed of a charged, a scalar and a pseudoscalar. The CP-odd component of the singlet scalar, after supersymmetry breaking, takes the role of a pseudo-Nambu-Goldstone mode in the $Z_3$ symmetric case, while the CP-even one becomes decoupled. In a second part of our study we investigate the different decay processes allowed to a charged Higgs boson of this model. Specifically, we search for general signatures of the TNMSSM in order to distinguish among Higgs fields belonging to $SU(2)$ doublet, triplet and singlet representations at the LHC. We also propose few golden plated final state modes carrying the distinctive signatures of this model which could be investigated in collider searches. We also show how in the decoupling limit of the triplet ($|\lambda_T| \simeq 0$) affects the decays as well as the production channels at the LHC.

Few remarks on the Higgs boson decays in gauge-Higgs unification

In the scenario of gauge-Higgs unification, the origin of the Higgs boson is higher dimensional gauge boson. Reflecting its origin, very characteristic predictions are made of the Higgs boson interactions in this scenario. Especially, a remarkable claim has been made: the contribution of non-zero Kaluza-Klein modes to the Higgs decay $H \to Z \gamma$ exactly vanishes in the minimal SU(3) electro-weak unified model, at least at the one-loop level. In this brief report, in order to see whether this prediction is a general feature of the scenario or the consequence of the specific choice of the model, matter content or the order of perturbative expansion, we perform an operator analysis. We demonstrate that there does not exist any relevant operator, respecting the gauge symmetry SU(3) in the bulk. We also comment on the possibly important contribution to the photonic decay $H \to \gamma \gamma$ due to the non-zero Kaluza-Klein modes of light quarks.

Probing new physics of cubic Higgs boson interaction via Higgs pair production at hadron colliders

Despite the discovery of a Higgs boson $h$ (125 GeV) at the LHC run 1, its self-interaction has fully evaded direct experimental probe so far. Such self-interaction is vital for electroweak symmetry breaking, vacuum stability, and electroweak phase transition. It is a most likely place to encode new physics beyond the standard model. We parametrize such new physics by model-independent dimension-six effective operators and study their tests via Higgs pair production at hadron colliders. We analyze three major di-Higgs production channels at the parton level and compare the parameter dependence of total cross sections and kinematic distributions at the LHC (14 TeV) and $pp$ (100 TeV) hadron collider. We further perform full simulations for the di-Higgs production channel $gg\ensuremath{\rightarrow}hh\ensuremath{\rightarrow}b\overline{b}\ensuremath{\gamma}\ensuremath{\gamma}$ and its backgrounds at the $pp$ (100 TeV) hadron collider. We construct four kinds of benchmark points and study the sensitivities to probing different regions of the parameter space of cubic Higgs interactions. We find that for a one-parameter analysis and with a $3\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$ ($30\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$) integrated luminosity, the $gg\ensuremath{\rightarrow}hh\ensuremath{\rightarrow}b\overline{b}\ensuremath{\gamma}\ensuremath{\gamma}$ channel can measure the SM cubic Higgs coupling and the derivative cubic Higgs coupling to an accuracy of about 13% (4.2%) and 5% (1.6%), respectively.

Gravitational Waves, Newton’s Law and Coulomb's Law Interpreted by Particle Radiation and Interaction Theory Based on Yangton & Yington Theory

The structures of Photon, Higgs Boson, Electron, and Positron are proposed based on “Wu’s Particle”, a Yangton and Yington circulating pair. Gravitational Force is generated by the attractive force through close contact between two Higgs Bosons of String Structures made of “Wu’s Particles” having the same circulation direction. Electrical Forces are formed by either attractive or repulsive forces via close contact between Electrons and Positions/Protons. Higgs Boson Radiation and Electron Radiation with Inverse Square Law and Contact Interactions, defined as “Particle Radiation and Interaction Theory”, are proposed as the mechanisms to explain Newton’s Law of Universal Gravitation and Coulomb’s Law of Electrical Forces. Furthermore, Gravitational Waves instead of ripples of space-time, are in fact the fluctuation of the total Gravitational Forces of two merging Black Holes detected in Line of Sight by Earth observers. This can be interpreted by Higgs Boson Radiation and Interaction Theory based on Yangton & Yington Theory.

Measurements of the properties of the Higgs boson using the ATLAS detector

Measurements of the properties of the Higgs boson with the ATLAS detector are presented. The spin, parity and tensor couplings of the Higgs boson in the H → γγ , H → ZZ* → 4l and H → WW* → evμv channels are investigated. The results are based on pp collision data collected by the ATLAS detector corresponding to an integrated luminosity of 4.7 fb−1 at centre-of-mass energy √s = 7 TeV, and 20.3 fb−1 at √s = 8 TeV. Measurements of the fiducial and differential cross sections for Higgs boson production in the H → γγ and H → ZZ* → 4l are also presented using 20.3 fb−1 of √s = 8 TeV data. The cross section measurements in the H → γγ channel are then used to set limits on anomalous Higgs boson interactions in an effective Lagrangian. All results are consistent with expectations for a Standard Model Higgs boson.

Constraints on non-Standard Model Higgs boson interactions in an effective Lagrangian using differential cross sections measured in the H → γγ decay channel at [formula omitted] with the ATLAS detector

The strength and tensor structure of the Higgs boson's interactions are investigated using an effective Lagrangian, which introduces additional CP-even and CP-odd interactions that lead to changes in the kinematic properties of the Higgs boson and associated jet spectra with respect to the Standard Model. The parameters of the effective Lagrangian are probed using a fit to five differential cross sections previously measured by the ATLAS experiment in the H→γγ decay channel with an integrated luminosity of 20.3 fb−1 at s=8 TeV. In order to perform a simultaneous fit to the five distributions, the statistical correlations between them are determined by re-analysing the H→γγ candidate events in the proton–proton collision data. No significant deviations from the Standard Model predictions are observed and limits on the effective Lagrangian parameters are derived. The statistical correlations are made publicly available to allow for future analysis of theories with non-Standard Model interactions.

Effects of two inert scalar doublets on Higgs boson interactions and the electroweak phase transition

We study some implications of the presence of two inert scalar doublets which are charged under a dark Abelian gauge symmetry. Specifically, we investigate the effects of the new scalars on oblique electroweak parameters and on the interactions of the 125 GeV Higgs boson, especially its decay modes $h\to\gamma\gamma,\gamma Z$, and trilinear coupling, all of which will be probed with improved precision in future Higgs measurements. Moreover, we explore how the inert scalars may give rise to strongly first-order electroweak phase transition and also show its correlation with sizable modifications to the Higgs trilinear coupling.

Model-independent probe of anomalous heavy neutral Higgs bosons at the LHC

We first formulate, in the framework of effective Lagrangian, the general form of the effective interactions of the lightest Higgs boson h and a heavier neutral Higgs boson H in a multi-Higgs system taking account of Higgs mixing effect. We regard h as the discovered Higgs boson which has been shown to be consistent with the standard model (SM) Higgs boson. The obtained effective interactions contain extra parameters reflecting the Higgs mixing effect. Next, We study the constraints on the anomalous coupling constants of H from both the requirement of the unitarity of the S matrix and the exclusion bounds on the SM Higgs boson obtained from the experimental data at the 7--8 TeV LHC. From this we obtain the available range of the anomalous coupling constants of H, with which H is not excluded by the yet known theoretical and experimental constraints. We then study the signatures of H at the 14 TeV LHC. In this paper, we suggest taking weak-boson scattering and pp to VH* to VVV as sensitive processes for probing H model independently at the 14 TeV LHC. We take several examples with the anomalous HVV coupling constants in the available ranges to do the numerical study. a full tree-level calculation at the hadron level is given with signals and backgrounds carefully calculated. We impose a series of proper kinematic cuts to effectively suppress the backgrounds. It is shown that, in both the VV scattering and the pp to VH* to VVV processes, H boson can be discovered from the invariant mass distributions of the final state particles with reasonable integrated luminosity. Especially, in the pp to VH* to VVV process, the invariant mass distribution of the final state jets can show a clear resonance peak of H. Finally, we propose several physical observables from which the values of the anomalous coupling constants f_W and f_{WW} can be measured experimentally.

Higgs boson gluon–fusion production at threshold in N3LO QCD

We present the cross-section for the threshold production of the Higgs boson at hadron-colliders at next-to-next-to-next-to-leading order (N3LO) in perturbative QCD. We present an analytic expression for the partonic cross-section at threshold and the impact of these corrections on the numerical estimates for the hadronic cross-section at the LHC. With this result we achieve a major milestone towards a complete evaluation of the cross-section at N3LO which will reduce the theoretical uncertainty in the determination of the strengths of the Higgs boson interactions.

Phenomenology of the Higgs effective Lagrangian via FeynRules

The Higgs discovery and the lack of any other hint for new physics favor a description of non-standard Higgs physics in terms of an effective field theory. We present an implementation of a general Higgs effective Lagrangian containing operators up to dimension six in the framework of FeynRules and provide details on the translation between the mass and interaction bases, in particular for three- and four-point interaction vertices involving Higgs and gauge bosons. We illustrate the strengths of this implementation by using the UFO interface of FeynRules capable to generate model files that can be understood by the MadGraph 5 event generator and that have the specificity to contain all interaction vertices, without any restriction on the number of external legs or on the complexity of the Lorentz structures. We then investigate several new physics effects in total rates and differential distributions for different Higgs production modes, including gluon fusion, associated production with a gauge boson and di-Higgs production. We finally study contact interactions of gauge and Higgs bosons to fermions.

'Higgsogenesis' proposed to explain dark matter

Interactions of Higgs bosons and anti-Higgs in early Universe may also have caused asymmetry between matter and antimatter.

On gauge invariance and minimal coupling

Abstract The principle of minimal coupling has been used in the study of Higgs boson interactions to argue that certain higher dimensional operators in the low-energy effective theory generalization of the Standard Model are suppressed by loop factors, and thus smaller than others. It also has been extensively used to analyze beyond-the-Standard-Model theories. We show that in field theory, and even in quantum mechanics, the concept of minimal coupling is ill-defined and inapplicable as a general principle, and give many pedagogical examples which illustrate this fact. We also clarify some related misconceptions about the dynamics of strongly coupled gauge theories. Many arguments in the literature on Higgs boson interactions that use minimal coupling, particularly in pseudo-Goldstone Higgs theories, are inherently flawed.

Constraining anomalous Higgs boson interactions

The recently announced Higgs boson discovery marks the dawn of the direct probing of the electroweak symmetry breaking sector. Sorting out the dynamics responsible for electroweak symmetry breaking now requires probing the Higgs boson interactions and searching for additional states connected to this sector. In this work, we analyze the constraints on Higgs boson couplings to the standard model gauge bosons using the available data from Tevatron and LHC. We work in a model-independent framework expressing the departure of the Higgs boson couplings to gauge bosons by dimension-six operators. This allows for independent modifications of its couplings to gluons, photons, and weak gauge bosons while still preserving the Standard Model (SM) gauge invariance. Our results indicate that best overall agreement with data is obtained if the cross section of Higgs boson production via gluon fusion is suppressed with respect to its SM value and the Higgs boson branching ratio into two photons is enhanced, while keeping the production and decays associated to couplings to weak gauge bosons close to their SM prediction.

The Higgs sector of the minimal B−L model at future Linear Colliders

We investigate the phenomenology of the Higgs sector of the minimal B−L extension of the Standard Model at a future e + e − Linear Collider. We consider the discovery potential of both a sub-TeV and a multi-TeV machine. We show that, within such a theoretical scenario, several novel production and decay channels involving the two physical Higgs states, precluded at the LHC, could experimentally be accessed at such machines. Amongst these, several Higgs signatures have very distinctive features with respect to those of other models with enlarged Higgs sector, as they involve interactions of Higgs bosons between themselves, with Z′ bosons as well as with heavy neutrinos. In particular, we present the scope of the Z′ strahlung process for single and double Higgs production, the only suitable mechanism enabling one to access an almost decoupled heavy scalar state (therefore outside the LHC range).

Standard Model, Higgs Boson(s) and New Physics at the LHC in Run I

A overview of the ATLAS and CMS detectors and first physics results from the 2010 data taking campaign at the LHC collider is presented. Measurements with pp collisions at s = 7 TeV and for integrated luminosities reaching up to about 40 pb −1 are summarized for weak bosons and top quark production, as well as for the search of the Higgs Boson(s), supersymmetry and new interactions at the TeV scale. The physics prospects for the complete Run I from 2010 to 2012 with a few fb −1 of luminosity collected per experiment are discussed.

Phenomenology of the minimalB−Lextension of the standard model: The Higgs sector

We investigate the phenomenology of the Higgs sector of the minimal $B\ensuremath{-}L$ extension of the standard model. We present results for both the foreseen energy stages of the Large Hadron Collider ($\sqrt{s}=7$ and 14 TeV). We show that in such a scenario several novel production and decay channels involving the two physical Higgs states could be accessed at such a machine. Amongst these, several Higgs signatures have very distinctive features with respect to those of other models with an enlarged Higgs sector, as they involve interactions of Higgs bosons between themselves, with ${Z}^{\ensuremath{'}}$ bosons as well as with heavy neutrinos.

Flavor-changing neutral current in production and decay of pseudoscalar mesons in a type III two-Higgs-doublet-model with four-texture Yukawa couplings

We study flavor violating processes in the production or decay of a neutral pseudoscalar meson $P^0$ in the framework of a general two Higgs Doublet Model type III (2HDM-III). We use a version of the model where Yukawa interactions of neutral Higgs bosons allow for flavor change at the tree-level, but conserves CP symmetry. We focus on all possible $\tau^{\pm} \to l^{\pm}P^0 $ and $P^0 \to l^+l'^-$ decay channels, where $l,l'$ are charged leptons. We find that these processes provide complementary information on quark and lepton FCNC Yukawa couplings. In particular flavor violating parameters in the quark sector, $\chi_{sb}$ and $\chi_{db}$, are significantly constrained by present experimental data, whereas the corresponding parameters in the leptonic sector are less constrained.

Model-independent description and Large Hadron Collider implications of suppressed two-photon decay of a light Higgs boson

For a standard model Higgs boson with mass between 115 GeV and 150 GeV, the two-photon decay mode is important for discovery at the Large Hadron Collider (LHC). We describe the interactions of a light Higgs boson in a more model-independent fashion and consider the parameter space where there is no two-photon decay mode. We argue from generalities that analysis of the tth discovery mode outside its normal thought of range of applicability is especially needed under these circumstances. We demonstrate the general conclusion with a specific example of parameters of a type I two-Higgs doublet theory, motivated by ideas in strongly coupled model building. We then specify a complete set of branching fractions and discuss the implications for the LHC.