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.

The anomalous case of axion EFTs and massive chiral gauge fields

We study axion effective field theories (EFTs), with a focus on axion couplings to massive chiral gauge fields. We investigate the EFT interactions that participate in processes with an axion and two gauge bosons, and we show that, when massive chiral gauge fields are present, such interactions do not entirely originate from the usual anomalous EFT terms. We illustrate this both at the EFT level and by matching to UV-complete theories. In order to assess the consistency of the Peccei-Quinn (PQ) anomaly matching, it is useful to introduce an auxiliary, non-dynamical gauge field associated to the PQ symmetry. When applied to the case of the Standard Model (SM) electroweak sector, our results imply that anomaly-based sum rules between EFT interactions are violated when chiral matter is integrated out, which constitutes a smoking gun of the latter. As an illustration, we study a UV-complete chiral extension of the SM, containing an axion arising from an extended Higgs sector and heavy fermionic matter that obtains most of its mass by coupling to the Higgs doublets. We assess the viability of such a SM extension through electroweak precision tests, bounds on Higgs rates and direct searches for heavy charged matter. At energies below the mass of the new chiral fermions, the model matches onto an EFT where the electroweak gauge symmetry is non-linearly realised.

Searching for heavy Higgs in supersymmetric final states at the LHC

In this work, we analyse and demonstrate possible strategies to explore extended Higgs sector of the Minimal Supersymmetric Standard Model (MSSM). In particular we concentrate on heavy Higgs decays to electroweakinos. We analyse the Higgs to electroweakino decays in the allowed MSSM parameter space after taking into account 13 TeV LHC searches for supersymmetric particles and phenomenological constraints such as flavour physics, Higgs measurements and dark matter constraints. We explore some novel aspects of these Higgs decays. The final states resulting from Higgs to electroweakino decays will have backgrounds arising from the Standard Model as well as direct electroweakino production at the LHC. We demonstrate explicit kinematical differences between Higgs to electroweakino decays and associated backgrounds. Furthermore, we demonstrate for a few specific example points, optimised analysis search strategies at the high luminosity LHC (HL-LHC) run. Finally, we comment on possible search strategies for heavy Higgs decays to exotic final states, where the lightest chargino is long lived and leads to a disappearing track at the LHC.

Understanding the MiniBooNE and the muon and electron g − 2 anomalies with a light Z′ and a second Higgs doublet

Two of the most widely studied extensions of the Standard Model (SM) are a) the addition of a new U(1) symmetry to its existing gauge groups, and b) the expansion of its scalar sector to incorporate a second Higgs doublet. We show that when combined, they allow us to understand the electron-like event excess seen in the MiniBooNE (MB) experiment as well as account for the observed anomalous values of the muon magnetic moment. A light Z′ associated with an additional U(1) coupled to baryons and to the dark sector, with flavor non-universal couplings to leptons, in conjunction with a second Higgs doublet is capable of explaining the MB excess. The Z′ obtains its mass from a dark singlet scalar, which mixes with the two Higgs doublets. Choosing benchmark parameter values, we show that $$ \mathrm{U}{(1)}_{B-3{L}_{\tau }} $$ U 1 B − 3 L τ , which is anomaly-free, and U(1)B, both provide (phenomenologically) equally good solutions to the excess. We also point out the other (anomaly-free) U(1) choices that may be possible upon fuller exploration of the parameter space. We obtain very good matches to the energy and angular distributions for neutrinos and anti-neutrinos in MB. The extended Higgs sector has two light CP-even scalars, h′ and H , and their masses and couplings are such that in principle, both contribute to help explain the MB excess as well as the present observed values of the muon and electron g − 2. We discuss the constraints on our model as well as future tests. Our work underlines the role that light scalars may play in understanding present-day low-energy anomalies. It also points to the possible existence of portals to the dark sector, i.e., a light gauge boson field (Z′) and a dark neutrino which mixes with the active neutrinos, as well as a dark sector light scalar which mixes with the extended Higgs sector.

Towards Higgs masses and decay widths satisfying the symmetries in the (N)MSSM

In models with an extended Higgs sector, such as the (N)MSSM, scalar states mix with one another. Yet, the concept of Higgs mixing is problematic at the radiative level, since it introduces both a scheme and a gauge dependence. In particular, the definition of Higgs masses and decay amplitudes can be impaired by the presence of gauge-violating pieces of higher order. We discuss in depth the origin and magnitude of such effects and consider two strategies that minimize the dependence on the gauge-fixing parameter and field-renormalization of one-loop order in the definition of the mass and decay observables, both in degenerate and non-degenerate scenarios. In addition, the intuitive concept of mixing and the simplicity of its definition in terms of two-point diagrams can make it tempting to include higher-order corrections on this side of the calculation, irrespectively of the order achieved in vertex diagrams. Using the global $$SU(2)_{\mathrm{L}}$$ S U ( 2 ) L -symmetry in the decoupling limit, we show that no improvement can be expected from such an approach at the level of the Higgs decays, but that, on the contrary, the higher-order terms may lead to numerically large spurious effects.

HL-LHC and ILC sensitivities in the hunt for heavy Higgs bosons

The prediction of additional Higgs bosons is one of the key features of physics beyond the Standard Model (SM) that gives rise to an extended Higgs sector. We assess the sensitivity of the Large Hadron Collider (LHC) in the high luminosity (HL) run alone and in combination with a possible future International Linear Collider (ILC) to probe heavy neutral Higgs bosons. We employ the Minimal Supersymmetric Standard Model (MSSM) as a framework and assume the light $$\mathcal {CP}$$ CP -even MSSM Higgs boson to be the Higgs boson observed at $$125\,\mathrm{GeV}$$ 125 GeV . We discuss the constraints on the MSSM parameter space arising from the precision measurements of the rates of the detected signal at $$125\,\mathrm{GeV}$$ 125 GeV and from direct searches for new heavy Higgs bosons in the $$\tau ^+\tau ^-$$ τ + τ - , $$b\bar{b}$$ b b ¯ and di-Higgs (hh) final states. A new benchmark scenario for heavy Higgs searches in the $$b\bar{b}$$ b b ¯ channel is proposed in this context. For the future Higgs rate measurements at the HL-LHC and ILC two different scenarios are investigated, namely the case where the future rate measurements agree with the SM prediction and the case where the rates agree with the predictions of possible realizations of the MSSM Higgs sector in nature.

Prospects for direct searches for light Higgs bosons at the ILC with 250 GeV

The particle discovered in the Higgs boson searches at the LHC with a mass of about 125 GeV is compatible within the present uncertainties with the Higgs boson predicted in the Standard Model (SM), but it could also be identified with one of the neutral Higgs bosons in a variety of beyond the SM (BSM) theories with an extended Higgs sector. The possibility that an additional Higgs boson (or even more than one) could be lighter than the state that has been detected at 125 GeV occurs generically in many BSM models and has some support from slight excesses that were observed above the background expectations in Higgs searches at LEP and at the LHC. The couplings between additional Higgs fields and the electroweak gauge bosons in BSM theories could be probed by model-independent Higgs searches at lepton colliders. We present a generator-level extrapolation of the limits obtained at LEP to the case of a future $$e^+e^-$$ e + e - collider, both for the search where the light Higgs boson decays into a pair of bottom quarks and for the decay-mode-independent search utilising the recoil method. We find that at the ILC with a centre-of-mass energy of 250 GeV, an integrated luminosity of 500 fb$$^{-1}$$ - 1 and polarised beams, the sensitivity to a light Higgs boson with reduced couplings to gauge bosons is improved by more than an order of magnitude compared to the LEP limits and goes much beyond the projected indirect sensitivity of the HL-LHC with 3000 fb$$^{-1}$$ - 1 from the rate measurements of the detected state at 125 GeV.

Extended Higgs sector of 2HDM with real singlet facing LHC data

We study the phenomenology of the two Higgs doublet model with a real singlet scalar S (N2HDM). The model predicts three CP-even Higgses $$h_{1,2,3}$$h1,2,3, one CP-odd $$A^0$$A0 and a pair of charged Higgs. We discuss the consistency of the N2HDM with theoretical as well as with all available experimental data. In contrast with previous studies, we focus on the scenario where $$h_2$$h2 is the Standard Model (SM) 125 GeV Higgs, while $$h_1$$h1 is lighter than $$h_2$$h2 which may open a window for Higgs to Higgs decays. We perform an extensive scan into the parameter space of N2HDM of type I and explore the effect of the singlet-doublet admixture. We found that a large singlet-doublet admixture is still compatible with the recent Higgs data from LHC. Moreover, we show that $$h_1$$h1 could be quasi-fermiophobic and would decay dominantly into two photons. We also study in details the consistency of the non-detected decay of $$h_2\rightarrow h_1 h_1$$h2→h1h1 with LHC data followed by $$h_1\rightarrow \gamma \gamma $$h1→γγ which leads to four photons final state at LHC: $$pp\rightarrow h_2\rightarrow h_1 h_1\rightarrow 4\gamma $$pp→h2→h1h1→4γ. Using the results of null searches of multi-photons carried by the ATLAS collaboration, we have found that a large area of the parameter space is still allowed. We also demonstrate that various neutral Higgs of the N2HDM could have several exotic decays.