two-Higgs-doublet Model Research Articles

The general Two-Higgs Doublet Model in a gauge-invariant form

In the general Two-Higgs Doublet Model it has been shown that the Higgs potential can be expressed in terms of gauge-independent quantities that transform covariantly under unitary mixing of the doublets. In particular, stability, electroweak symmetry breaking, and CP symmetry can be understood in a concise way, avoiding unphysical gauge degrees of freedom. We complete this program and show how all the masses, the trilinear and quartic scalar interactions, the gauge-boson-Higgs interactions, as well as the Yukawa couplings in the general THDM can be expressed in a gauge-invariant way.

Additional Higgs bosons: Supersymmetry or warped extra dimensions?

We investigate and compare additional CP-even, CP-odd and charged scalar states appearing in two popular Beyond the Standard Model scenarios. We focus on the simplest possible Higgs sector within warped extra-dimensions and supersymmetry, with the aim to differentiate between them. In each case, we analyze the couplings of the new Higgs states, looking for distinguishing signatures. We show that the couplings of the Standard Model gauge bosons to the first Kaluza-Klein Higgs states of the extra-dimensional setup (CP-even, CP-odd and charged) are very similar to those of the heavy Higgs states of the MSSM in the decoupling region. We also find that the Yukawa couplings in the extra-dimensional scenario can mimic the different types of Yukawa couplings of general Two-Higgs Doublet Models, in particular the so-called Type-II couplings, which are similar to those in the MSSM.

Fine-tuning in the 2HDM

The Two-Higgs Doublet Model (2HDM) is one of the most popular and natural extensions of the Higgs sector; but it has two potential fine-tuning problems, related to the electroweak (EW) breaking and the requirement of alignment with the SM Higgs boson. We have quantified the fine-tunings obtaining analytical expressions, both in terms of the initial 2HDM parameters and the physical ones (masses, mixing angles, etc.). We also provide simple approximate expressions. We have taken into account that the fine-tunings are not independent and removed the “double counting” by projecting the variations of the alignment onto the constant-v^2 hypersurface. The EW and the alignment fine-tunings become severe in different, even opposite, regions of the parameter space, namely in the regimes of large and small extra-Higgs masses, respectively; emerging an intermediate region, 500~{textrm{GeV}} {mathop {{}_sim }limits ^{<}}{m_H, m_A, m_{H^pm }} {mathop {{}_sim }limits ^{<}}700~{textrm{GeV}}, where both are acceptably small. We also discuss a remarkable trend that is not obvious at first glance. Namely, for large tan beta both the EW and the alignment fine-tunings become mitigated. In consequence, the 2HDM becomes quite natural for tan beta ge {mathcal {O}} (10), even if m_H, m_A, m_{H^pm } are as large as 1500 GeV. We explain why this is not the case for the 2HDM stemming from supersymmetry. We have illustrated all these trends by numerically analyzing several representative scenarios.

Laser-assisted CP-odd and CP-even Higgs bosons production in THDM

In this paper, we have theoretically studied the neutral Higgs pair production in Two Higgs Doublet Model (THDM) in the presence of a circularly polarized laser field. The laser-assisted differential partial cross section is derived in the centre of mass frame at the leading order including Z diagram. The total cross section is computed numerically by integrating the differential cross section over the solid angle . Two benchmark points are discussed for the THDM parameters. In the first step, we have analysed the total cross section of by considering H 0 as the standard model (SM)-like Higgs boson. Then, the process is studied by taking h 0 as the Higgs boson of the SM. For both benchmark points, the laser-assisted total cross section of the studied processes depends on the produced neutral Higgs masses, the centre of mass energy and the laser field parameters. In addition, the maximum cross section occurs at high centre of mass energy for the process as compared to that of .

Models with two Higgs doublets and a light pseudoscalar: A portal to dark matter and the possible (g−2)μ excess

In the context of a two-Higgs doublet model, supplemented by an additional light pseudoscalar Higgs boson and a stable isosinglet fermion, we consider the possibility of addressing simultaneously the discrepancy from the standard expectation of the anomalous magnetic moment of the muon recently measured at Fermilab and the longstanding problem of the dark matter in the universe which can be accounted for by a thermal weakly interacting massive particle. We show that it is indeed possible, for a range of masses and couplings of the new light pseudoscalar and the fermionic states, to explain at the same time the two features while satisfying all other constraints from astroparticle physics and collider searches, including the constraints from flavor physics.

Electroweak precision fit and new physics in light of the W boson mass

The $W$ boson mass is one of the most important electroweak precision observables for testing the Standard Model (SM) or its extensions. The very recent measured $W$ boson mass at the Collider Detector at Fermilab (CDF) shows about $7\ensuremath{\sigma}$ deviations from the SM prediction, which may challenge the internal consistency of the SM. By performing the global electroweak fit with the new $W$ boson, we present the new values of the oblique parameters: $S=0.06\ifmmode\pm\else\textpm\fi{}0.10$, $T=0.11\ifmmode\pm\else\textpm\fi{}0.12$, $U=0.13\ifmmode\pm\else\textpm\fi{}0.09$, or $S=0.14\ifmmode\pm\else\textpm\fi{}0.08$, $T=0.26\ifmmode\pm\else\textpm\fi{}0.06$ with $U=0$ and the corresponding correlation matrices, which strongly indicates the need for the nondegenerate multiplets beyond the SM. As a proof-of-concept, we show that the new results can be accommodated in the two-Higgs doublet model, where the charged Higgs boson has to be either heavier or lighter than both two heavy neutral Higgs bosons. The collider search for these non-SM Higgs bosons will provide a complementary way to test the new physics for $W$ boson mass anomaly.

Electroweak renormalization based on gauge-invariant vacuum expectation values of non-linear Higgs representations. Part II. Extended Higgs sectors

A recently proposed scheme for a gauge-invariant treatment of tadpole corrections in spontaneously broken gauge theories — called Gauge-Invariant Vacuum expectation value Scheme (GIVS) — is applied to a singlet Higgs extension of the Standard Model and to the Two-Higgs Doublet Model. In contrast to previously used tadpole schemes, the GIVS unifies the gauge-invariance property with perturbative stability. For the Standard Model this was demonstrated for the conversion between on-shell and overline{mathrm{MS}} renormalized masses, where the GIVS leads to very moderate, gauge-independent electroweak corrections. In models with extended scalar sectors, issues with tadpole renormalization exist if Higgs mixing angles are renormalized with overline{mathrm{MS}} conditions, which is the major subject of this article. In detail, we first formulate non-linear representations of the extended scalar sectors, which is an interesting subject in its own right. Then we formulate the GIVS which employs these non-linear representations in the calculation of the tadpole renormalization constants, while actual higher-order calculations in the GIVS proceed in linear representations as usual. Finally, for the considered models we discuss the next-to-leading-order (electroweak and QCD) corrections to the decay processes h/H → WW/ZZ → 4 fermions of the CP-even neutral Higgs bosons h and H using overline{mathrm{MS}} -renormalized Higgs mixing angles with the GIVS and previously used tadpole treatments.

Mounting evidence for a 95 GeV Higgs boson

In 2018 CMS reported an excess in the light Higgs-boson search in the diphoton decay mode at about 95 GeV based on Run 1 and first year Run 2 data. The combined local significance of the excess was 2.8 σ. The excess is compatible with the limits obtained in the ATLAS searches from the diphoton search channel. Recently, CMS reported another local excess with a significance of 3.1 σ in the light Higgs-boson search in the di-tau final state, which is compatible with the interpretation of a Higgs boson with a mass of about 95 GeV. We show that the observed results can be interpreted as manifestations of a Higgs boson in the Two-Higgs Doublet Model with an additional real singlet (N2HDM). We find that the lightest Higgs boson of the N2HDM can fit both excesses simultaneously, while the second-lightest state is such that it satisfies the Higgs-boson measurements at 125 GeV, and the full Higgs-boson sector is compatible with all Higgs exclusion bounds from the searches at LEP, the Tevatron and the LHC as well as with other theoretical and experimental constraints. Finally, we demonstrate that it is furthermore possible to accommodate the excesses observed by CMS in the two search channels together with a local 2.3 σ excess in the boverline{b} final state observed at LEP in the same mass range.

Composite two-Higgs doublet model from dilaton effective field theory

We construct a composite two-Higgs-doublet model (2HDM) within the context of dilaton effective field theory. This EFT describes the particle spectrum observed in lattice simulations of a near-conformal SU(3) gauge field theory. A second Higgs doublet is naturally accommodated within the EFT, used previously to construct a one-Higgs-doublet model. We explore the interplay of phenomenological and EFT requirements, supplemented by information from numerical lattice studies of the SU(3) gauge theory with eight fundamental (Dirac) fermions. We build a viable model with moderate parameter tuning. In the relevant portion of parameter space, we match the model to a conventional general description of 2HDMs, and comment on the role of custodial symmetry (breaking) in the scalar potential. Contributions to the precision electroweak parameter T provide a possible explanation for the recent measurement of the W-boson mass by CDF II.

Probing double-aligned two-Higgs-doublet models at the LHC

We consider two Higgs doublet models (THDMs) with both the Higgs potential and Yukawa interactions being aligned, which we call ``double-aligned THDMs.'' In this scenario, coupling constants of the discovered Higgs boson to the Standard Model (SM) particles are identical to those of the SM Higgs boson, and flavor changing neutral currents via neutral Higgs bosons do not appear at tree level. We investigate current constraints and future prospects of the model by using measurements from flavor experiments and data of multilepton final states at LHC. Especially, we focus on the electroweak pair production of the additional Higgs bosons with their masses below $2{m}_{t}$. We find that the most of the parameter space are already excluded by the current LHC data when the leptonic decays of the additional Higgs bosons are dominant, which can be interpreted to the scenario in the Type-X THDM as a special case. We also clarify the parameter region where the high-luminosity LHC can explore, and demonstrate the reconstruction of the masses of additional Higgs bosons from the $b\overline{b}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ final states in a few benchmark points.

Possibility of a multi-step electroweak phase transition in the two-Higgs doublet models

Abstract We discuss whether a multi-step electroweak phase transition (EWPT) occurs in two-Higgs doublet models (2HDMs). The EWPT is related to interesting phenomena such as baryogenesis and the ensuing gravitational wave. We examine parameter regions in CP-conserving 2HDMs and find certain areas where multi-step EWPTs occur. The parameter search shows the multi-step EWPT prefers the scalar potential with the approximate Z2 symmetry and a mass hierarchy between the neutral CP-odd and CP-even extra scalar bosons mA &amp;lt; mH. By contrast, the multi-step EWPT whose first step is strongly first order favors a mass hierarchy mA &amp;gt; mH. In addition, we compute the Higgs trilinear coupling in the parameter region where multi-step EWPTs occur, which can be observed at future colliders. We also discuss a multi-peaked gravitational wave from a multi-step EWPT. Subject index B53, B59

SpaceMath version 1.0 A Mathematica package for beyond the standard model parameter space searches

We present a pedagogical Mathematica package, so-called SpaceMath, for Beyond the Standard Model parameter space searches. This software is directed mainly for the training of human resources related to elementary particle physics phenomenology, however, it is sophisticated enough to be used in researches. In this first version, SpaceMath v1.0 works with Higgs Boson Data whose results are the most up-to-date experimental measurements made at the Large Hadron Collider. In addition, we also include the expected results at future colliders, namely, High Luminosity LHC and High Energy LHC. SpaceMath v1.0 is able to find allowed regions for free parameters of extension models using the Higgs Boson Data within a friendly interface and an intuitive environment in which the user enters the couplings symbolically, sets parameters and execute Mathematica in the traditional way. As result, both tables as plots with values and areas agree with experimental data are generated. We present examples using SpaceMath v1.0 to analyze the free Two-Higgs Doublet Model and the Simplest Little Higgs Model parameter spaces, step by step, in order to start new users in a fast and efficient way. Finally, to validate SpaceMath v1.0, widely known results are reproduced.

The 28 GeV dimuon excess in lepton specific THDM

We explore the Higgs mass spectrum in a class of Two Higgs Doublet Models (THDMs) in which a scalar SU(2)L doublet interacts only with quarks, while the second one interacts only with leptons. The spectrum includes two CP-even Higgs bosons, either of which can account for the SM-like Higgs boson, and the spectra involving light Higgs bosons receive strong impacts from the LEP results and the current collider analyses. We find that a consistent spectrum can involve a CP-odd Higgs boson as light as about 10 GeV, while the lightest CP-even Higgs boson cannot be lighter than about 55 GeV when mA∼28 GeV. These analyses can rather bound the low tan⁡β region which can also accommodate an observed excess in dimuon events at mμμ∼28 GeV. A lepton-specific class of THDMs (LS-THDM) can predict such an excess through A→μμ decays, while the solutions can be constrained by the A→ττ mode. After constraining the solutions with the consistent ranges of σ(pp→bbA→bbττ), a largest excess at about 1.5σ at 8 TeV center of mass (COM) energy and 2σ at 13 TeV COM is observed for tan⁡β∼12 and mA∼28 GeV in the σ(pp→bbA→bbμμ) events.

Two-loop prediction of the anomalous magnetic moment of the muon in the Two-Higgs Doublet Model with GM2Calc 2

We present an extension of the GM2Calc software to calculate the muon anomalous magnetic moment ({a_mu ^{{text {BSM}}}}) in the Two-Higgs Doublet Model. The Two-Higgs Doublet Model is one of the simplest and most popular extensions of the Standard Model. It is one of the few single field extensions that can give large contributions to {a_mu ^{{text {BSM}}}}. It is essential to include two-loop corrections to explain the long standing discrepancy between the Standard Model prediction and the experimental measurement in the Two-Higgs Doublet Model. The new version GM2Calc 2 implements the state of the art two-loop calculation for the general, flavour violating Two-Higgs Doublet Model as well as for the flavour aligned Two-Higgs Doublet Model and the type I, II, X and Y flavour conserving variants. Input parameters can be provided in either the gauge basis or the mass basis, and we provide an easy to use SLHA-like command-line interface to specify these. Using this interface users may also select between Two-Higgs Doublet Model types and choose which contributions to apply. In addition, GM2Calc 2 also provides interfaces in C++, C, Python and Mathematica, to make it easy to interface with other codes.

Particle Dark Matter Density and Entropy Production in the Early Universe

Dark Matter (DM) density is reduced if entropy production takes place after DM particles abundance is frozen out in the early universe. We study a possibility of such reduction due to entropy production in the electroweak phase transition (EWPT). We compare scenarios of entropy production in the standard model (SM) and its simplest extension, the two-Higgs doublet model (2HDM). Assuming the EWPT is of second order in the SM scenario and the first order in the 2HDM, we calculate the entropy release in these scenarios and the corresponding dilution of preexisting DM density in the early universe. We find the effect of dilution in EWPT significant for confrontation with observations of any form of possible DM (including primordial black holes (PBHs)), which is frozen out, decoupled, frozen in, or formed before EWPT.

New Light H± Discovery Channels at the LHC

A light charged Higgs boson has been searched for at the Large Hadron Collider (LHC) via top (anti)quark decay, i.e., t→bH+, if kinematically allowed. In this contribution, we propose new channels for light charged Higgs boson searches via the pair productions pp→H±h/A and pp→H+H− at the LHC in the context of the Two-Higgs Doublet Model (2HDM) Type-I. By focusing on a case where the heavy H state is the Standard Model (SM)-like one already observed, we investigate the production of the aforementioned charged Higgs bosons and their bosonic decay channels, namely, H±→W±h and/or H±→W±A. We demonstrate that such production and decay channels can yield substantial alternative discovery channels for H± bosons at the LHC. Finally, we propose eight benchmark points (BPs) to motivate the search for such signatures.

Radiative corrections to decays of charged Higgs bosons in two Higgs doublet models

We calculate the next-to-leading order (NLO) electroweak (EW) corrections to decay rates of charged Higgs bosons for various decay modes in the four types of two Higgs doublet models (THDMs) with the softly broken discrete Z2 symmetry. Decay branching ratios of charged Higgs bosons are evaluated including NLO EW corrections, as well as QCD corrections up to next-to-next-to-leading order (NNLO). We comprehensively study impacts of the NLO EW corrections to the branching ratios in nearly alignment scenarios where the couplings constants of the Higgs boson with the mass of 125 GeV are close to those predicted in the standard model. Furthermore, in the nearly alignment scenario, we discuss whether or not the four types of THDMs can be distinguished via the decays of charged Higgs bosons. We find that characteristic predictions of charged Higgs branching ratios can be obtained for all types of the THDMs, by which each type of the THDMs is separated, and information on the internal parameters of the THDMs can be extracted from the magnitudes of the various decay branching ratios.

New physics explanations of a\u03bc in light of the FNAL muon g \u2212 2 measurement

The Fermilab Muon g −2 experiment recently reported its first measurement of the anomalous magnetic moment {a}_{mu}^{mathrm{FNAL}} , which is in full agreement with the previous BNL measurement and pushes the world average deviation Delta {a}_{mu}^{2021} from the Standard Model to a significance of 4.2σ. Here we provide an extensive survey of its impact on beyond the Standard Model physics. We use state-of-the-art calculations and a sophisticated set of tools to make predictions for aμ, dark matter and LHC searches in a wide range of simple models with up to three new fields, that represent some of the few ways that large ∆aμ can be explained. In addition for the particularly well motivated Minimal Supersymmetric Standard Model, we exhaustively cover the scenarios where large ∆aμ can be explained while simultaneously satisfying all relevant data from other experiments. Generally, the aμ result can only be explained by rather small masses and/or large couplings and enhanced chirality flips, which can lead to conflicts with limits from LHC and dark matter experiments. Our results show that the new measurement excludes a large number of models and provides crucial constraints on others. Two-Higgs doublet and leptoquark models provide viable explanations of aμ only in specific versions and in specific parameter ranges. Among all models with up to three fields, only models with chirality enhancements can accommodate aμ and dark matter simultaneously. The MSSM can simultaneously explain aμ and dark matter for Bino-like LSP in several coannihilation regions. Allowing under abundance of the dark matter relic density, the Higgsino- and particularly Wino-like LSP scenarios become promising explanations of the aμ result.

A final word on FCNC-Baryogenesis from two Higgs doublets

Electroweak baryogenesis in a two-Higgs doublet model is a well-motivated and testable scenario for physics beyond the Standard Model. An attractive way of providing CP violation is through flavor-changing Higgs couplings, where the top-charm coupling is hardly constrained. This minimal scenario can be tested by searching for heavy charged and neutral Higgs bosons at the LHC. While the charged Higgs signature requires a dedicated analysis, the neutral Higgs signature will be covered by a general search for same-sign top pairs. Together, they provide a conclusive test of this kind of baryogenesis.

Finger printing the presence of extra scalars in the h \u2192 Vff\u2032 forward-backward asymmetry

In this work we analyse the forward-backward asymmetry of the h → V f f′ decay in the Aligned two-Higgs Doublet Model. The Standard Model prediction for this asymmetry for V = W is small, as it suffers from Yukawa suppression and is absent for V = Z. This does not necessarily have to hold true in the Aligned model where these contributions can in principle be re-enhanced through the independent alignment factors ςf. In this analysis we conclude that, due to the additional contributions corresponding to the Aligned two-Higgs Doublet Model together with extra sources of CP-violation for the V = Z channel, the Standard Model predictions can be significantly modified in a great region of the parameter space. These deviations, that could be potentially measured at the High Luminosity LHC or future Higgs factories, would be a clear signal of new physics, and would shed new light on the possible extensions of the Standard Model and new sources of CP-violation.