The $$R^2$$-Higgs inflation with two Higgs doublets

We study $$R^2$$ R 2 -Higgs inflation in a model with two Higgs doublets in which the Higgs sector of the Standard Model is extended by an additional Higgs doublet, thereby four scalar fields are involved in the inflationary evolutions. We first derive the set of equations required to follow the inflationary dynamics in this two Higgs doublet model, allowing a nonminimal coupling between the Higgs-squared and the Ricci scalar R, as well as the $$R^2$$ R 2 term in the covariant formalism. By numerically solving the system of equations, we find that, in parameter space where a successful $$R^2$$ R 2 -Higgs inflation are realized and consistent with low energy constraints, the inflationary dynamics can be effectively described by a single slow-roll formalism even though four fields are involved in the model. We also argue that the parameter space favored by $$R^2$$ R 2 -Higgs inflation requires nearly degenerate masses for $$m_{\mathsf {H}}$$ m H , $$m_A$$ m A and $$m_{{\mathsf {H}}^{\pm }}$$ m H ± , where $${\mathsf {H}}$$ H , A, and $${\mathsf {H}}^{\pm }$$ H ± are the extra CP even, CP odd, and charged Higgs bosons in the general two Higgs doublet model taking renormalization group evolutions of the parameters into account. Discovery of such heavy scalars at the Large Hadron Collider (LHC) are possible if they are in the sub-TeV mass range. Indirect evidences may also emerge at the LHCb and Belle-II experiments, however, to probe the quasi degenerate mass spectra one would likely require high luminosity LHC or future lepton colliders such as the International Linear Collider and the Future Circular Collider.

Unitarity violation and the geometry of Higgs EFTs

We derive the scale of unitarity violation from the geometry of Effective Field Theory (EFT) extensions of the Standard Model Higgs sector. The high-energy behavior of amplitudes with more than four scalar legs depends on derivatives of geometric invariants with respect to the physical Higgs field h, such that higher-point amplitudes begin to reconstruct the scalar manifold away from our vacuum. In theories whose low-energy limit can be described by the Higgs EFT (HEFT) but not the Standard Model EFT (SMEFT), non-analyticities in the vicinity of our vacuum limit the radius of convergence of geometric invariants, leading to unitarity violation at energies below 4πv. Our results unify approaches to the HEFT/SMEFT dichotomy based on unitarity, analyticity, and geometry, and more broadly illustrate the sense in which observables probe the geometry of an EFT. Along the way, we provide novel basis-independent results for Goldstone/Higgs boson scattering amplitudes expressed in terms of geometric covariant quantities.

Exploration of Extended Higgs Sectors with Run-2 Proton–Proton Collision Data at the LHC

One doublet of complex scalar fields is the minimal content of the Higgs sector in order to achieve spontaneous electroweak symmetry breaking and, in turn, to generate the masses of fundamental particles in the Standard Model. However, several theories beyond the Standard Model predict a nonminimal Higgs sector and introduce additional singlets, doublets or even higher-order weak isospin representations, thereby yielding additional Higgs bosons. With its high proton–proton collision energy (13 TeV during Run-2), the Large Hadron Collider opens a new window towards the exploration of extended Higgs sectors. This review article summarises the current state-of-the-art experimental results recently obtained in searches for new neutral and charged Higgs bosons with a partial or full Run-2 dataset.

SO(10) models with A4 modular symmetry

We combine SO(10) Grand Unified Theories (GUTs) with A4 modular symmetry and present a comprehensive analysis of the resulting quark and lepton mass matrices for all the simplest cases. We focus on the case where the three fermion families in the 16 dimensional spinor representation form a triplet of Γ3 ≃ A4, with a Higgs sector comprising a single Higgs multiplet H in the 10 fundamental representation and one Higgs field $$ \overline{\Delta } $$ ∆ ¯ in the $$ \overline{\mathbf{126}} $$ 126 ¯ for the minimal models, plus one Higgs field Σ in the 120 for the non-minimal models, all with specified modular weights. The neutrino masses are generated by the type-I and/or type II seesaw mechanisms and results are presented for each model following an intensive numerical analysis where we have optimized the free parameters of the models in order to match the experimental data. For the phenomenologically successful models, we present the best fit results in numerical tabular form as well as showing the most interesting graphical correlations between parameters, including leptonic CP phases and neutrinoless double beta decay, which have yet to be measured, leading to definite predictions for each of the models.

Leptonic g − 2 anomaly in an extended Higgs sector with vector-like leptons

We address the observed discrepancies in the anomalous magnetic dipole moments (MDM) of the muon and electron by extending the inert two Higgs Doublet Model (2HDM) with SM gauge singlet complex scalar field and singlet Vector-like Lepton (VLL) field. We obtain the allowed parameter space constrained from the Higgs decays to gauge Bosons at LHC, LEP II data and electro-weak precision measurements. The muon and electron MDM’s are then explained within a common parameter space for different sets of allowed couplings and masses of the model particles.

Resolving the (g − 2)μ discrepancy with $$ \mathcal{F} $$–SU(5) intersecting D-branes

A discrepancy between the measured anomalous magnetic moment of the muon (g − 2)μ and computed Standard Model value now stands at a combined 4.2σ following experiments at Brookhaven National Lab (BNL) and the Fermi National Accelerator Laboratory (FNAL). A solution to the disagreement is uncovered in flipped SU(5) with additional TeV-Scale vector-like 10 + $$ \overline{\mathbf{10}} $$ 10 ¯ multiplets and charged singlet derived from local F-Theory, collectively referred to as $$ \mathcal{F} $$ F –SU(5). Here we engage general No-Scale supersymmetry (SUSY) breaking in $$ \mathcal{F} $$ F –SU(5) D-brane model building to alleviate the (g −2)μ tension between the Standard Model and observations. A robust ∆aμ(SUSY) is realized via mixing of M5 and M1X at the secondary SU(5) × U(1)X unification scale in $$ \mathcal{F} $$ F –SU(5) emanating from SU(5) breaking and U(1)X flux effects. Calculations unveil ∆aμ(SUSY) = 19.0–22.3 × 10−10 for gluino masses of M($$ \overset{\sim }{g} $$ g ~ )= 2.25–2.56 TeV and higgsino dark matter, aptly residing within the BNL+FNAL 1σ mean. This (g − 2)μ favorable region of the model space also generates the correct light Higgs boson mass and branching ratios of companion rare decay processes, and is further consistent with all LHC Run 2 constraints. Finally, we also examine the heavy SUSY Higgs boson in light of recent LHC searches for an extended Higgs sector.

Reconciling Higgs physics and pseudo-Nambu-Goldstone dark matter in the S2HDM using a genetic algorithm

We investigate a possible realization of pseudo-Nambu-Goldstone (pNG) dark matter in the framework of a singlet-extended 2 Higgs doublet model (S2HDM). pNG dark matter gained attraction due to the fact that direct-detection constraints can be avoided naturally because of the momentum-suppressed scattering cross sections, whereas the relic abundance of dark matter can nevertheless be accounted for via the usual thermal freeze-out mechanism. We confront the S2HDM with a multitude of theoretical and experimental constraints, paying special attention to the theoretical limitations on the scalar potential, such as vacuum stability and perturbativity. In addition, we discuss the complementarity between constraints related to the dark matter sector, on the one hand, and to the Higgs sector, on the other hand. In our numerical discussion we explore the Higgs funnel region with dark matter masses around 60 GeV using a genetic algorithm. We demonstrate that the S2HDM can easily account for the measured relic abundance while being in agreement with all relevant constraints. We also discuss whether the so-called center-of-galaxy excesses can be accommodated, possibly in combination with a Higgs boson at about 96 GeV that can be the origin of the LEP- and the CMS-excess observed at this mass in the b$$ \overline{b} $$ b ¯ -quark and the diphoton final state, respectively.

Two-loop $$ \mathcal{O} $$((αt + αλ + ακ)2) corrections to the Higgs boson masses in the CP-violating NMSSM

We present our computation of the $$ \mathcal{O} $$ O ((αt + αλ + ακ)2) two-loop corrections to the Higgs boson masses of the CP-violating Next-to-Minimal Supersymmetric Standard Model (NMSSM) using the Feynman-diagrammatic approach in the gaugeless limit at vanishing external momentum. We choose a mixed $$ \overline{\mathrm{DR}} $$ DR ¯ -on-shell (OS) renormalisation scheme for the Higgs sector and apply both $$ \overline{\mathrm{DR}} $$ DR ¯ and OS renormalisation in the top/stop sector. For the treatment of the infrared divergences we apply and compare three different regularisation methods: the introduction of a regulator mass, the application of a small momentum expansion, and the inclusion of the full momentum dependence. Our new corrections have been implemented in the Fortran code NMSSMCALC that computes the Higgs mass spectrum of the CP-conserving and CP-violating NMSSM as well as the Higgs boson decays including the state-of-the-art higher-order corrections. Our numerical analysis shows that the newly computed corrections increase with rising λ and κ, remaining overall below about 3% compared to our previously computed $$ \mathcal{O} $$ O (αt(αt + αs)) corrections, in the region compatible with perturbativity below the GUT scale. The renormalisation scheme and scale dependence is of typical two-loop order. The impact of the CP-violating phases in the new corrections is small. We furthermore show that the Goldstone Boson Catastrophe due to the infrared divergences can be treated in a numerically efficient way by introducing a regulator mass that approximates the momentum-dependent results best for squared mass values in the permille range of the squared renormalisation scale. Our results mark another step forward in the program of increasing the precision in the NMSSM Higgs boson observables.

Composite Higgs revealed in Higgs pair photo-production at future colliders

The next generation electron-positron colliders are designed for precision studies of the Standard Model and its extensions, in particular in the Higgs sector. We consider the potential for discovery of composite Higgs models in Higgs pair production through photon collisions. This process is loop-generated, thus it provides access to all Higgs couplings and can show new physics effects in polarized and unpolarized cross-sections starting at relatively low collider energies. It is, therefore, relevant for all electron-positron colliders planned or in preparation. Sizeable deviations from the Standard Model predictions are present in a general class of composite Higgs models, as couplings of one or more Higgs bosons to fermions, or fermionic and scalar resonances, modify the destructive interference present in the Standard Model. In particular, large effects are due to the new quartic coupling of the Higgs to tops and to the presence of a light scalar resonance.