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1. A natural mechanism for approximate Higgs alignment in the 2HDM

   https://doi.org/10.1007/JHEP05(2021)235  

   Draper, Patrick ; Ekstedt, Andreas ; Haber, Howard E. ( May 2021 , Journal of High Energy Physics)

   null (Ed.)

   A bstract The 2HDM possesses a neutral scalar interaction eigenstate whose tree-level properties coincide with the Standard Model (SM) Higgs boson. In light of the LHC Higgs data which suggests that the observed Higgs boson is SM-like, it follows that the mixing of the SM Higgs interaction eigenstate with the other neutral scalar interaction eigenstates of the 2HDM should be suppressed, corresponding to the so-called Higgs alignment limit. The exact Higgs alignment limit can arise naturally due to a global symmetry of the scalar potential. If this symmetry is softly broken, then the Higgs alignment limit becomes approximate (although still potentially consistent with the current LHC Higgs data). In this paper, we obtain the approximate Higgs alignment suggested by the LHC Higgs data as a consequence of a softly broken global symmetry of the Higgs Lagrangian. However, this can only be accomplished if the Yukawa sector of the theory is extended. We propose an extended 2HDM with vector-like top quark partners, where explicit mass terms in the top sector provide the source of the soft symmetry breaking of a generalized CP symmetry. In this way, we can realize approximate Higgs alignment without a significant fine-tuning of the model parameters. We then explore the implications of the current LHC bounds on vector-like top quark partners for the success of our proposed scenario. 

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2. Endoscopic decompositions and the Hausel–Thaddeus conjecture

   https://doi.org/10.1017/fmp.2021.7  

   Maulik, Davesh ; Shen, Junliang ( January 2021 , Forum of Mathematics, Pi)

   Abstract We construct natural operators connecting the cohomology of the moduli spaces of stable Higgs bundles with different ranks and genera which, after numerical specialisation, recover the topological mirror symmetry conjecture of Hausel and Thaddeus concerning $\mathrm {SL}_n$ - and $\mathrm {PGL}_n$ -Higgs bundles. This provides a complete description of the cohomology of the moduli space of stable $\mathrm {SL}_n$ -Higgs bundles in terms of the tautological classes, and gives a new proof of the Hausel–Thaddeus conjecture, which was also proven recently by Gröchenig, Wyss and Ziegler via p -adic integration. Our method is to relate the decomposition theorem for the Hitchin fibration, using vanishing cycle functors, to the decomposition theorem for the twisted Hitchin fibration, whose supports are simpler. 

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3. Distinguishing 6d (1,0) SCFTs: an extension to the geometric construction

   Distler, Jacques ; Kang, Monica ; Lawrie, Craig ( March 2022 , ArXivorg)

   We provide a new extension to the geometric construction of 6d (1, 0) SCFTs that encap- sulates Higgs branch structures with identical global symmetry but different spectra. In particular, we find that there exist distinct 6d (1, 0) SCFTs that may appear to share their tensor branch description, flavor symmetry algebras, and central charges. For example, such subtleties arise for the very even nilpotent Higgsing of (so4k,so4k) conformal matter; we pro- pose a method to predict at which conformal dimension the Higgs branch operators of the two theories differ via augmenting the tensor branch description with the Higgs branch chiral ring generators of the building block theories. Torus compactifications of these 6d (1, 0) SCFTs give rise to 4d N = 2 SCFTs of class S and the Higgs branch of such 4d theories are cap- tured via the Hall–Littlewood index. We confirm that the resulting 4d theories indeed differ in their spectra in the predicted conformal dimension from their Hall–Littlewood indices. We highlight how this ambiguity in the tensor branch description arises beyond the very even nilpotent Higgsing of (so4k,so4k) conformal matter, and hence should be understood for more general classes of 6d (1, 0) SCFTs. 

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4. Quantum collider probes of the fermionic Higgs portal

   https://doi.org/10.21468/SciPostPhys.16.4.112  

   Haisch, Ulrich ; Ruhdorfer, Maximilian ; Schmid, Konstantin ; Weiler, Andreas ( January 2024 , SciPost Physics)

   We explore the sensitivity of future hadron colliders to constrain the fermionic Higgs portal, with a focus on scenarios where the new fermions cannot be directly observed in exotic Higgs decays. This portal emerges in various models including twin-Higgs scenarios and dark matter models, posing significant challenges for collider tests. Working in an effective field theory (EFT), we determine the reach of the high-luminosity option of the Large Hadron Collider (HL-LHC), the high-energy upgrade of the LHC (HE-LHC) and a proposed Future Circular Collider (FCC) in probing the fermionic Higgs portal through off-shell and double-Higgs production. Notably, we find that quantum-enhanced indirect probes offer a better sensitivity than other direct Higgs measurements. We argue that this finding is valid in a wide class of ultraviolet realisations of the EFT. Our study presents a roadmap of a multifaceted search strategy for exploring the fermionic Higgs portal at forthcoming hadron machines.

    

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5. Multi-Higgs boson production with anomalous interactions at current and future proton colliders

   https://doi.org/10.1007/JHEP06(2024)124  

   Papaefstathiou, Andreas ; Tetlalmatzi-Xolocotzi, Gilberto ( June 2024 , Journal of High Energy Physics)

   We investigate multi-Higgs boson production at proton colliders, in a framework involving anomalous interactions, focusing on triple Higgs boson production. We consider modifications to the Higgs boson self-couplings, to the Yukawa interactions, as well as new contact interactions of Higgs bosons with either quarks or gluons. To this end, we have developed a MadGraph5_aMC@NLO loop model, publicly available, designed to incorporate the relevant operators in the production of multiple Higgs bosons (and beyond). We have performed cross section fits at various energies over the anomalous interactions, and have derived constraints on the most relevant anomalous coefficients, through detailed phenomenological analyses at proton-proton collision energies of 13.6 TeV and 100 TeV, employing the 6 b-jet final state. 

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