Inert Higgs Doublet Research Articles

Unveiling desert region in inert doublet model assisted by Peccei-Quinn symmetry

The Inert Higgs Doublet model (IDM), assisted by Peccei-Quinn (PQ) symmetry, offers a simple but natural framework of a dark sector that accommodates Weakly Interacting Massive Particle (WIMP) and axion as dark matter components. Spontaneous breaking of U(1)PQ symmetry, which was originally proposed as an elegant solution to the strong charge-parity (CP) problem, also ensures the stability of WIMP through a residual ℤ2 symmetry. Interestingly, additional fields necessitated by PQ symmetry further enrich the dark sector. These include a scalar field proprietor for axion DM and a vector-like quark (VLQ) that acts as a portal for the dark sector through Yukawa interactions. Moreover, this combination of the axion and WIMP components satisfies the observed DM relic density and reopens the phenomenologically exciting region of the IDM parameter space where the WIMP mass falls between 100 - 550 GeV. We investigate the model-independent pair production of VLQs exploring this region at the Large Hadron Collider (LHC), incorporating the effects of next-to-leading order (NLO) QCD corrections. After production, each VLQ decays into a top or bottom quark accompanied by an inert scalar, a consequence of the residual ℤ2 symmetry. Utilising relevant observables with a leptonic search channel and employing multivariate analysis, we demonstrate the ability of this analysis to exclude a significant portion of the parameter space with an integrated luminosity of 300 fb−1.

Top-quark FCNC decays, LFVs, lepton g − 2, and W mass anomaly with inert charged Higgses

The observed flavor-changing neutral-current (FCNC) processes in the standard model (SM) arise from the loop diagrams involving the weak charged currents mediated by the W-gauge boson. Nevertheless, the top-quark FCNCs and lepton flavor-violating processes resulting from the same mechanism are highly suppressed. We investigate possible new physics effects that can enhance the suppressed FCNC processes, such as a top quark decaying into a light quark with a Higgs or gauge boson in the final state, i.e. t → q(h, V) with V = γ, Z, g, h→ℓℓ′ , and ℓ→ℓ′γ . To achieve the assumption that the induced FCNCs are all from quantum loops, we consider the scotogenic mechanism, where a Z 2 symmetry is introduced and only new particles carry an odd Z 2 parity. With the extension of the SM to include an inert Higgs doublet, an inert charged Higgs singlet, a vector-like singlet quark, and two neutral leptons, it is found that, with relevant constraints taken into account, the t → c(h, Z), h → μ τ, and τ → ℓ γ decays can be enhanced up to the expected sensitivities in experiments. The branching ratios of h → μ + μ −/τ + τ − from only new physics effects can reach up to O(10−3) . Intriguingly, the resulting muon g − 2 can fit the combined data within 2 standard deviations, whereas the electron g − 2 can have either sign with a magnitude of O(10−13−10−12) . In addition, we examine the oblique parameters in the model and find that the resulting W-mass anomaly observed by CDF II can be accommodated.

Interplay of inert doublet and vector-like lepton triplet with displaced vertices at the LHC/FCC and MATHUSLA

We study the interaction between the inert Higgs doublet (IDM) dark matter and a vector-like SU(2) triplet lepton (VLL), both of which are Z2-odd. The vector current of the VLL with the Z-boson rules out a fermionic or two-component dark matter scenario. However, a compressed mass spectrum and a sufficiently small Yukawa coupling allows co-annihilation and late decay of the VLL into the IDM sector, affecting the relic density of the pseudoscalar dark matter. The same two factors enable displaced decay of the VLL states, providing novel signatures involving hadronically quiet displaced multi-lepton final states. Such signatures to probe the model are studied at the 14 and 27 TeV LHC, as well as the 100 TeV FCC-hh. In addition to being detectable at the CMS/ATLAS experiments, if the new particles have sub-100 GeV masses, signals can also be seen at the proposed MATHUSLA detector.

Analysis of the process e+e- → h0a0 in ihdm in the presence of a linearly polarized laser field

We consider the process of neutral Higgs production from e+e- annihilation in Inert Higgs Doublet Model (IHDM) in the absence and presence of an external eld. The latter is assumed to be a plane and monochro-matic wave with linear polarization. In the theoretical framework, we present the analytic calculation of the lowest order di erential cross section by using the scattering matrix approach and Dirac-Volkov formalism for charged incident particles. The total cross section is computed by performing a numerical integration of the di erential cross section over the solid angle. The results obtained are analyzed and discussed for di erent centre of mass energies and laser parameters. We found that inserting a laser wave with linear polarization is a suitable mechanism to enhance the total cross-section of the process. Indeed, the probability of the process to occur increases with the presence of a linearly polarized laser eld, especially with low frequency and high strength.

Scrutinizing a hidden SM-like gauge model with corrections to oblique parameters

In view of the recent high precision measurement of the Standard Model W boson mass at the CDF II detector, we compute the contributions to the oblique parameters S, T and U coming from the two additional Higgs doublets (one inert and one hidden) as well as the hidden neutral dark gauge bosons and extra heavy fermions in the gauged two-Higgs-doublet model (G2HDM). While the effects from the hidden Higgs doublet and new heavy fermions are found to be minuscule, the hidden gauge sector SU(2)_H times U(1)_X with gauge coupling strength gtrsim 10^{-2} and gauge boson mass gtrsim 100 GeV can readily explain the W boson mass anomaly but is nevertheless excluded by the dilepton high-mass resonance searches at the Large Hadron Collider. On the other hand, the new global fits to the oblique parameters due to the new W boson mass measurement can give discernible impacts on the mass splitting and mixing angle for the inert Higgs doublet in G2HDM. We also study the impact on the signal strength of diphoton mode of the 125 GeV Higgs boson h rightarrow gamma gamma and the detectability of the yet to be observed process h rightarrow Z gamma at the High Luminosity Large Hadron Collider. Current constraints for the dark matter candidate W^prime including the dark matter relic density, dark matter direct detections and invisible Higgs decays are also taken into account in this study.

Dark matter in a singlet-extended inert Higgs-doublet model

In this work, we consider an extension of the Standard Model with an inert Higgs doublet and a real scalar singlet, in order to address problems around the origin of dark matter (DM). In this model, the lightest among the $CP$-odd and $CP$-even neutral inert components plays the role of a DM candidate, where the model parameters are subject to many theoretical and experimental constraints. These constraints include vacuum stability, perturbativity, LEP negative searches, electroweak precision tests, Higgs diphoton, Higgs invisible and Higgs undetermined decays, DM relic density, and DM direct detection bounds. Using these constraints, we find that the allowed parameter space for these models is quite sizable and could be explored in upcoming collider and astrophysical searches.

Interpreting electroweak precision data including the W-mass CDF anomaly

We perform a global fit of electroweak data, finding that the anomaly in the W mass claimed by the CDF collaboration can be reproduced as a universal new-physics correction to the T parameter or |H†DμH|2 operator. Contributions at tree-level from multi-TeV new physics can fit the anomaly compatibly with collider bounds: we explore which scalar vacuum expectation values (such as a triplet with zero hypercharge), Z′ vectors (such as a Z′ coupled to the Higgs only), little-Higgs models or higher-dimensional geometries provide good global fits. On the other hand, new physics that contributes at loop-level must be around the weak scale to fit the anomaly. Thereby it generically conflicts with collider bounds, that can be bypassed assuming special kinematics like quasi-degenerate particles that decay into Dark Matter (such as an inert Higgs doublet or appropriate supersymmetric particles).

Scalar triplet flavor leptogenesis with dark matter

We investigate a simple variant of type-II seesaw, responsible for neutrino mass generation, where the particle spectrum is extended with one singlet right-handed neutrino and an inert Higgs doublet, both odd under an additional $Z_2$ symmetry. While the role of the dark matter is played by the lightest neutral component of the inert Higgs doublet, its interaction with the Standard Model lepton doublets and the right-handed neutrino turns out to be crucial in generating the correct baryon abundance of the Universe through flavored leptogenesis from the decay of the $SU(2)_L$ scalar triplet, involved in type-II framework.

Laser-assisted charged Higgs pair production in Inert Higgs Doublet Model (IHDM)

The production of a pair of charged Higgs bosons from e+e− annihilation in the presence of a circularly polarized laser field is investigated in Inert Higgs doublet Model (IHDM) at e+e− colliders. We have derived the analytical expression for the laser-assisted differential cross section by using the Dirac-Volkov formalism at leading order including the Z and γ diagrams. Since the laser-free cross section of this process depends, in the lowest order, only on the mass of the charged Higgs boson and the energy of the center of mass, we have analyzed the dependence of the total laser-assisted cross section on these parameters and also on the laser parameters such as the number of photons exchanged, the laser field intensity and its frequency. The results found indicate that the electromagnetic field decreases the order of magnitude of the total cross section as much as the laser field intensity increases or by decreasing its frequency. Moreover, it becomes high for low charged Higgs masses and low center of mass energies.

Laser-assisted neutral Higgs-boson pair production in Inert Higgs Doublet Model (IHDM)

In the framework of the Inert Higgs Doublet model (IHDM), we have investigated, in the centre of mass frame, the neutral Higgs-boson pair production in the presence of an intense and circularly polarized laser field via e+e− annihilation (e+e−→H0A0) at the lowest order. By using the scattering matrix method, we have derived the analytical expression of the differential cross section. The latter is numerically integrated over the solid angle to obtain the total cross section. Then, we have shown how this total cross section depends on the outgoing particles mass for different number of exchanged photons. Next, we have illustrated its variation as a function of the centre of mass energy for different neutral Higgs-boson masses. Finally, we have indicated how it changes as a function of the laser field amplitudes for both different number of exchanged photons and different neutral Higgs-bosons masses.

One-loop radiative corrections to e+e\u2212 \u2192 Zh0/H0A0 in the Inert Higgs Doublet Model

We compute the full one-loop radiative corrections (including both weak and QED corrections) for two processes e+e− → Zh0, H0A0 in the Inert Higgs Doublet model (IHDM). Up to O(αw) and O(αem) order, we use FeynArts/FormCalc to compute the one-loop virtual corrections and Feynman Diagram Calculation (FDC) to evaluate the real emission, respectively. Being equipped with these computing tools, we investigate radiative corrections of new physics for five scenarios with three typical collision energies of future electron-positron colliders: 250 GeV, 500 GeV, and 1000 GeV. By scanning the parameter space of IHDM, we identify the allowed regions which are consistent with constraints and bounds, from both theoretical and experimental sides. We find that the radiative corrections of the IHDM to e+e− → Zh0 can be sizeable and are within the detection potentials of future Higgs factories. We also find that the new physics of IHDM could also be directly detected by observing the process e+e− → H0A0 which could have large enough production rate. We propose six benchmark points and examine their salient features which can serve as physics targets for future electron-positron colliders, such as CEPC/CLIC/FCC-ee/ILC as well as for LHC.

Neutrino mass and asymmetric dark matter: study with inert Higgs doublet and high scale validity

We consider an inert Higgs doublet (IHD) extension of the Standard Model accompanied with three right handed neutrinos and a dark sector, consisting of a singlet fermion and a scalar, in order to provide a common framework for dark matter, leptognesis and neutrino mass. While the Yukawa coupling of the right handed neutrinos with IHD (having mass in the intermediate regime: 80–500 GeV) is responsible for explaining the observed baryon asymmetry through leptogenesis, its coupling with the dark sector explains the dark matter relic density. The presence of IHD also explains the neutrino mass through radiative correction. We find that study of the high scale validity of the model in this context becomes crucial as it restricts the parameter space significantly. It turns out that there exists a small, but non-zero contribution to the relic density of DM from IHD too. Considering all the constraints from dark matter, leptogenesis, neutrino mass and high scale validity of the model, we perform a study to find out the viable parameter space.

Scalar dark matter and leptogenesis in the minimal scotogenic model

We study the minimal scotogenic model constituting an additional inert Higgs doublet and three sets of right-handed neutrinos. The scotogenic model connects dark matter, baryon asymmetry of the Universe and neutrino oscillation data. In our work, we obtain baryogenesis by the decay of TeV scale heavy neutral singlet fermion (N2). We primarily focus on the intermediate-mass region of dark matter within MW<MDM≤550 GeV, where observed relic density is suppressed due to co-annihilation processes. We consider thermal as well as the non-thermal approach of dark matter production and explore the possibility of the lightest stable candidate being a dark matter candidate. Within the inert Higgs doublet (IHD) desert, we explore a new allowed region of dark matter masses for the non-thermal generation of dark matter with a mass splitting of 10 GeV among the inert scalars. We also see the variation of relic abundance for unequal mass splitting among the scalars. The KamLand-Zen bound on the effective mass of the active neutrinos is also verified in this study.

New mechanism for matter-antimatter asymmetry and connection with dark matter

We propose a new mechanism for generating matter-antimatter asymmetry via the interference of tree-level diagrams only, where the imaginary part of the Breit-Wigner propagator for an unstable mediator plays a crucial role. We first derive a general result that a nonzero $CP$-asymmetry can be generated via at least two sets of interfering tree-level diagrams involving either $2\rightarrow2$ or $1\rightarrow n$ (with $n\geq3$) processes. We illustrate this point in a simple TeV-scale extension of the Standard Model with an inert Higgs doublet and right-handed neutrinos, along with an electroweak-triplet scalar field, where small Majorana neutrino masses are generated via a combination of radiative type-I and tree-level type-II seesaw mechanisms. The imaginary part needed for the required $CP$-asymmetry comes from the trilinear coupling of the inert doublet with the triplet scalar, along with the width of the triplet scalar mediator. The real part of the neutral component of the inert doublet serves as a cold dark matter candidate. The evolutions of the dark matter relic density and the baryon asymmetry are intimately related in this scenario.

Two component dark matter with inert Higgs doublet: neutrino mass, high scale validity and collider searches

The idea of this work is to investigate the constraints on the dark matter (DM) allowed parameter space from high scale validity (absolute stability of Higgs vacuum and perturbativity) in presence of multi particle dark sector and heavy right handed neutrinos to address correct neutrino mass. We illustrate a simple two component DM model, consisting of one inert SU(2)L scalar doublet and a scalar singlet, both stabilised by additional {mathcal{Z}}_2times {mathcal{Z}}_2^{prime } symmetry, which also aid to vacuum stability. We demonstrate DM-DM interaction helps achieving a large allowed parameter space for both the DM components by evading direct search bound. High scale validity puts further constraints on the model, for example, on the mass splitting between the charged and neutral component of inert doublet, which has important implication to its leptonic signature(s) at the Large Hadron Collider (LHC).

Mono-Higgs signature in the scotogenic model with Majorana dark matter

We study the phenomenology of scotogenic model in the case of Majorana Dark Matter (DM) candidate. This scenario gives important consequences since the parameter space of the model is almost unconstrained compared to the Inert Higgs Doublet Model (or the scotogenic model with scalar DM), and hence, offers new opportunities for discovery at future high energy collider, e.g. the HL-LHC. As an example, we focus on the production of the Standard Model (SM) Higgs boson in association with a pair of dark scalars. Owing to its clean signature, the $\gamma\gamma$ decay channel of the SM Higgs boson is investigated in great detail at both the HL-LHC (at $\sqrt{s}=14$ TeV) and the future FCC-hh (at $\sqrt{s}=100$ TeV). After revisiting the LHC constraints from run-II on the parameter space of the model, and selecting benchmark points satisfying all the theoretical and experimental constraints, we found that scalars with mass up to $140$ GeV ($160$ GeV) can be probed at the LHC (FCC-hh) with a $3$ ab$^{-1}$ of integrated luminosity assuming $5\%$ of uncertainty.

A simple model to explain observed muon sector anomalies and small neutrino masses

Since its inception, no decisive departure from the predictions of the standard model (SM) has been reported. However, recently various experiments have observed a few hints of possible departure from SM predictions in lepton flavor universality observables such as , , muon (g–2), , etc. Many of these are observable where deviation from the SM in the range of (2–4)σ is observed related to the muon (μ) lepton. So these deviations may hint at a possible new physics (NP) in the muon sector. In this work we extend the SM by introducing two SM singlet heavy charged leptons (Fe, Fμ), whose left-handed components are charged under a new U(1)F gauge symmetry, one color triplet lepto-quark (ϕQ) doublet under SU(2)L, one inert Higgs doublet (ϕl), and three very heavy Majorana neutrinos (NiR), all of which are odd under a Z2 discrete symmetry. One more scalar (ϕ) charged only under the U(1)F, whose VEV gives masses to the U(1)F gauge boson as well as the heavy leptons. With these new particles, we show that the observed anomalies in the muon sector as well as small neutrino masses can be explained taking into account all the other experimental and theoretical constraints to date.

Phenomenology of an extended IDM with loop-generated fermion mass hierarchies

We perform a comprehensive analysis of the most distinctive and important phenomenological implications of the recently proposed mechanism of sequential loop generation of strong hierarchies in the Standard Model (SM) fermion mass spectra. This mechanism is consistently realized at the level of renormalizable interactions in an extended variant of the Inert Higgs Doublet model, possessing the additional Z_{2}^{(1)}times Z_{2}^{(2)} discrete and U_{1X} gauge family symmetries, while the matter sectors of the SM are extended by means of SU_{2L}-singlet scalars, heavy vector-like leptons and quarks, as well as right-handed neutrinos. We thoroughly analyze the most stringent constraints on the model parameter space, coming from the Z^{prime } collider searches, related to the anomaly in lepton universality, and the muon anomalous magnetic moment, as well as provide benchmark points for further tests of the model and discuss possible “standard candle” signatures relevant for future explorations.

Sequentially loop-generated quark and lepton mass hierarchies in an extended Inert Higgs Doublet model

Extended scalar and fermion sectors offer new opportunities for generating the observed strong hierarchies in the fermion mass and mixing patterns of the Standard Model (SM). In this work, we elaborate on the prospects of a particular extension of the Inert Higgs doublet model where the SM hierarchies are generated sequentially by radiative virtual corrections in a fully renormalisable way, i.e. without adding any non-renormalisable Yukawa terms or soft-breaking operators to the scalar potential. Our model has a potential to explain the recently observed RK and RK∗ anomalies, thanks to the non universal U1X assignments of the fermionic fields that yield non universal Z′ couplings to fermions. We explicitly demonstrate the power of this model for generating the realistic quark, lepton and neutrino mass spectra. In particular, we show that due to the presence of both continuous and discrete family symmetries in the considered framework, the top quark acquires a tree-level mass, lighter quarks and leptons get their masses at one- and two-loop order, while neutrino masses are generated at three-loop level. The minimal field content, particle spectra and scalar potential of this model are discussed in detail.

Implications of hidden gauged U(1) model for B anomalies

We propose a hidden gauged $U(1)_H$ $Z'$ model to explain deviations from the Standard Model (SM) values in lepton flavor universality known as $R_K$ and $R_D$ anomalies. The $Z'$ only interacts with the SM fermions via their mixing with vector-like doublet fermions after the $U(1)_H$ symmetry breaking, which leads to $b \to s \mu\mu$ transition through the $Z^{\prime}$ at tree level. Moreover, introducing an additional mediator, inert-Higgs doublet, yields $b\to c \tau \nu$ process via charged scalar contribution at tree level. Using flavio package, we scrutinize adequate sizes of the relevant Wilson coefficients to these two processes by taking various flavor observables into account. It is found that significant mixing between the vector-like and the second generation leptons is needed for the $R_K$ anomaly. A possible explanation of the $R_D$ anomaly can also be simultaneously addressed in a motivated situation, where a single scalar operator plays a dominant role, by the successful model parameters for the $R_K$ anomaly.