Extending the Higgs sector of the standard model (SM) by just one additional Higgs doublet field leads to the two-Higgs-doublet model (2HDM). In the type-I <math><msub><mi>Z</mi><mn>2</mn></msub></math>-symmetric limit of the 2HDM, all the five new physical Higgs states can be fairly light, <math><mrow><mi>O</mi><mo>(</mo><mn>100</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> or less, without being in conflict with current data from the direct Higgs boson searches and the <math><mi>B</mi></math>-physics measurements. In this Letter, we establish that the new neutral as well as the charged Higgs bosons in this model can all be simultaneously observable in the multi-<math><mi>b</mi></math> final state. The statistical significance of the signature for each of these Higgs states, resulting from the electroweak (EW) production of their pairs, can exceed <math><mrow><mn>5</mn><mi>σ</mi></mrow></math> at the 13 TeV high-luminosity Large Hadron collider (HL-LHC). Since the parameter space configurations where this is achievable are precluded in the other, more extensively pursued, 2HDM types, an experimental validation of our findings would be a clear indication that the true underlying Higgs sector in nature is the type-I 2HDM.

Japan

India

Tanmoy Mondal

United Kingdom

Sweden

Stefano Moretti

Rwanda

United States

Shoaib Munir

South Korea

Prasenjit Sanyal

Electroweak Multi-Higgs Production: A Smoking Gun for the Type-I Two-Higgs-Doublet Model

We analyse the shifted hybrid inflation in a no-scale supersymmetric SU(5) GUT model which naturally circumvents the monopole problem. The no-scale framework is derivable as the effective field theory of the supersymmetric (SUSY) compactifications of string theory, and yields a flat potential with no anti-de Sitter vacua, resolving the η problem. The model predicts a scalar spectral tilt n  s  compatible with the most recent measurements by the Planck satellite, while also accommodating large values of the tensor-to-scalar ratio r (~ 0.0015), potentially measurable by the near-future experiments. Moreover, the proton decay lifetime in the presence of the dimension-5 operators is found to lie above the current limit imposed by the Super-Kamiokande experiment. A realistic scenario of reheating and non-thermal leptogenesis is employed, wherein the reheating temperature T  r  lies in the (2 × 106 ≲ T  r  ≲ 2 × 109) GeV range, and at the same time realizing gravitino as a viable dark matter (DM) candidate.

China

Waqas Ahmed

Pakistan

Muhammad Moosa

Umer Zubair

Observable r, gravitino dark matter, and non-thermal leptogenesis in no-scale supergravity

We perform a model-independent search for leptoquarks (LQs) at the Large Hadron Collider through their pair-production and subsequent decay into   <math> <mi>t</mi> <mover> <mi>t</mi> <mo>¯</mo> </mover> <mi>ττ</mi> </math>  $$ t\overline{t}\tau \tau $$  intermediate states. We show that, assuming full luminosity of the Run 2, a fully hadronic signal emerging from this intermediate state can surpass in sensitivity the established searches relying on leptons in the final state. Our conclusion is supported by a thorough Monte-Carlo analysis, and we advocate the deployment of our proposed search channel in the proper experimental setting of the Run 3. Furthermore, in order to highlight the full scope of this approach for constraining LQ theories, we interpret our results in the context of the string-inspired Exceptional Supersymmetric Standard Model, which naturally predicts the S 1-type scalar LQ states that we analyse here.

Murad Ali

Egypt

Shaaban Khalil

Russia

Roman Nevzorov

Alexandre Nikitenko

Harri Waltari

TeV-scale leptoquark searches at the LHC and their E6SSM interpretation

In the Next-to-Minimal Supersymmetric Standard Model there is a strong correlation between the mass terms corresponding to the singlet Higgs and the singlino interaction states, both of which are proportional to the parameter  $$\kappa $$  <math> <mi>κ</mi> </math>  . If this parameter is complex, explicit CP-violation occurs in the Higgs as well as the neutralino sectors of the model at the tree level, unlike in the minimal scenario. A small magnitude of  $$\kappa $$  <math> <mi>κ</mi> </math>   typically yields a  $${{\mathcal {O}}}$$  <math> <mi>O</mi> </math>  (10) GeV lightest neutralino with a dominant singlino component. In such a scenario, the phase of  $$\kappa $$  <math> <mi>κ</mi> </math>  , beside modifying the properties of the five Higgs bosons, can also have a crucial impact on the phenomenology of the neutralino dark matter. In this study we perform a first investigation of this impact on the relic abundance of the dark matter solutions with sub-100 GeV masses, obtained for parameter space configurations of the model that are consistent with a variety of current experimental data.

France

Mark Goodsell

Dark matter in the CP-violating NMSSM

New physics frameworks like the next-to-minimal supersymmetric standard Model and the Next-to-2-Higgs-doublet Model contain three neutral CP-even Higgs bosons. It is possible for the heavier two of these states to have masses identical to each other, which can result in a sizeable quantum interference between their propagators in processes they mediate. For both these models, we study the impact of such interference on the pair-production of the lightest of the three scalars, which we identify with the observed 125 GeV Higgs boson, in the gluon-fusion channel at the large hadron collider (LHC). We find that the inclusion of these effects can substantially alter the cross section, compared to its value when they are ignored, for this process. Our results illustrate the importance of taking possible quantum interference effects into account not only when investigating the phenomenology of extended Higgs sectors at the future Run(s) of the LHC, but also when imposing its current exclusion bounds on the parameter spaces of these models.

Biswaranjan Das

Canada

Poulose Poulose

Quantum interference effects in Higgs boson pair-production beyond the standard model

The two-Higgs Doublet Model (2HDM) is the most minimal extension of the Standard Model (SM) containing extra Higgs doublet fields. Given the multiplicity of Higgs states in a 2HDM, its Higgs potential is significantly more involved than the SM one. Importantly, it contains a multitude of Higgs triple self-couplings, unlike the SM, which only has one. These interactions are key to understanding the phenomenology of the 2HDM, as they uniquely determine the form of the potential. Several studies analysing the prospects of measuring these couplings at the Large Hadron Collider (LHC) have found them to be quite low generally. However, such studies have largely concentrated on Higgs pair-production induced by gluon-gluon scattering, either via direct annihilation or followed by their splitting into b-(anti)quark pairs, which in turn annihilate leaving behind spectator b-(anti)quarks. Both of these channels are therefore governed by QCD dynamics. We compare here the yields of such channels to those initiated by (primarily) valence quarks, which involve Electro-Weak (EW) interactions only, for neutral multi-Higgs final states. We find that EW production can be dominant over QCD production for certain final state combinations. We also illustrate that charged final states, which can only be produced via EW modes, could serve as important probes of some $$H^\pm $$ <math><msup><mi>H</mi><mo>±</mo></msup></math>  triple couplings, that are inaccessible in QCD-induced processes, during Run 2 and 3 of the LHC. Our analysis covers regions of the parameter space of the Type-I 2HDM that have escaped the most up-to-date experimental constraints coming from EW precision data, LHC measurements of the 125 GeV Higgs boson properties, searches for additional Higgs states, and flavour physics.

Rikard Enberg

William Klemm

Electroweak production of multiple (pseudo)scalars in the 2HDM

In the next-to-minimal supersymmetric standard model (NMSSM), it is possible to have strong mass degeneracies between the new singletlike scalar and the heavy doubletlike scalar, as well as between the singletlike and doubletlike pseudoscalar Higgs states. When the difference in the masses of such states is comparable with the sum of their widths, the quantum mechanical interference between their propagators can become significant. We study these effects by taking into account the full Higgs boson propagator matrix in the calculation of the production process of <math><mrow><msup><mrow><mi>τ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>τ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> pairs in gluon fusion at the Large Hadron Collider (LHC). We find that, while these interference effects are sizeable, they are not resolvable in terms of the distributions of differential cross sections, owing to the poor detector resolution of the <math><mrow><msup><mrow><mi>τ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>τ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> invariant mass. They are, however, identifiable via the inclusive cross sections, which are subject to significant variations with respect to the standard approaches, wherein the propagating Higgs bosons are treated independently from one another. We quantify these effects for several representative benchmark points, extracted from a large set of points, obtained by numerical scanning of the NMSSM parameter space, that satisfy the most important experimental constraints currently available.

Quantum interference among heavy NMSSM Higgs bosons

We analyse the phenomenological implications of a light Higgs boson, h , within the CP-conserving 2-Higgs Doublet Model (2HDM) Type-I, for the detection prospects of the charged HÂ± state at Run II of the Large Hadron Collider (LHC), assuming s=13 TeV as energy and O(100Â fbâ1) as luminosity. When sufficiently light, this h state can open up the bosonic decay channel HÂ±âWÂ±(â)h , which may have a branching ratio significantly exceeding those of the HÂ±âÏÎ½ and HÂ±âcs channels. We perform a broad scan of the 2HDM Type-I parameter space, assuming the heavier of the two CP-even Higgs bosons, H , to be the observed SM-like state with a mass near 125 GeV. Through these scans we highlight regions in which mHÂ±&lt;mt+mb that are still consistent with the most recent limits from experimental searches. We find in these regions that, when the HÂ±âWÂ±(â)h decay mode is the dominant one, the h can be highly fermiophobic, with a considerably large decay rate in the Î³Î³ channel. This can result in the total cross section of the Ï(ppâHÂ±hâWÂ±(â)+4Î³) process reaching up to O(100Â fb) . We therefore investigate the possibility of observing this spectacular signal at the LHC Run II.

Morocco

Abdesslam Arhrib

Rachid Benbrik

Identifying a light charged Higgs boson at the LHC Run II

In the next-to-minimal supersymmetric (NMS) Standard Model (SM), it is possible for either one of the additional singlet-like scalar and pseudoscalar Higgs bosons to be almost degenerate in mass with the â¼ 125 Â GeV SM-like Higgs state. In the real NMSSM (rNMSSM), when the mass difference between two scalar states is comparable to their individual total decay widths, the quantum mechanical interference, due to the relevant diagonal as well as off-diagonal terms in the propagator matrix, between them can become sizeable. This possibility invalidates usage of the narrow width approximation (NWA) to compute the cross section for the production of a di-photon pair with a given invariant mass via resonant Higgs boson(s) in the gluon fusion process at the Large Hadron Collider (LHC). When, motivated by the baryon asymmetry of the universe, CP-violating (CPV) phases are explicitly invoked in the Higgs sector of the NMSSM, all the interaction eigenstates mix to give five CP-indefinite physical Higgs bosons. In this scenario, the interference effects due to the off-diagonal terms in the Higgs mass matrix that mix the pseudoscalar-like state with the SM-like one can also become significant, when these two are sufficiently mass-degenerate. We perform a detailed analysis, in both the real and complex NMSSM, of these interference effects, when the full propagator matrix is taken into account, in the production of a photon pair with an invariant mass near 125Â GeV through gluon fusion. We find that these effects can account for up to â¼ 40 % of the total cross section for certain model parameter configurations. We also investigate how such mutually interfering states contributing to the â¼ 125 Â GeV signal observed at the LHC can be distinguished from a single resonance.

Two Higgs bosons near 125 GeV in the NMSSM: beyond the narrow width approximation

In models with extended Higgs sectors, it is possible that the Higgs boson discovered at the LHC is not the lightest one. We show that in a realistic model (the Type I 2-Higgs Doublet Model), when the sum of the masses of a light scalar and a pseudoscalar ( h and A ) is smaller than the Z boson mass, the Electroweak (EW) production of an hA pair can dominate over QCD production by orders of magnitude, a fact not previously highlighted. This is because in the gg -initiated process, hA production via a resonant Z in the s -channel is prohibited according to the Landau–Yang theorem, which is not the case for the qq¯ -initiated process. We explore the parameter space of the model to highlight regions giving such hA solutions while being consistent with all constraints from collider searches, b -physics and EW precision data. We also single out a few benchmark points to discuss their salient features, including the hA search channels that can be exploited at Run II of the LHC.

Electroweak production of light scalar–pseudoscalar pairs from extended Higgs sectors