Precision test of the muon-Higgs coupling at a high-energy muon collider

We explore the sensitivity of directly testing the muon-Higgs coupling at a high-energy muon collider. This is strongly motivated if there exists new physics that is not aligned with the Standard Model Yukawa interactions which are responsible for the fermion mass generation. We illustrate a few such examples for physics beyond the Standard Model. With the accidentally small value of the muon Yukawa coupling and its subtle role in the high-energy production of multiple (vector and Higgs) bosons, we show that it is possible to measure the muon-Higgs coupling to an accuracy of ten percent for a 10 TeV muon collider and a few percent for a 30 TeV machine by utilizing the three boson production, potentially sensitive to a new physics scale about Λ ∼ 30 − 100 TeV.

Singlino-dominated dark matter in general NMSSM

The general Next-to-Minimal Supersymmetric Standard Model (NMSSM) describes the singlino-dominated dark-matter (DM) property by four independent parameters: singlet-doublet Higgs coupling coefficient λ, Higgsino mass μtot, DM mass $$ {m}_{{\tilde{\chi}}_1^0} $$ m χ ˜ 1 0 , and singlet Higgs self-coupling coefficient κ. The first three parameters strongly influence the DM-nucleon scattering rate, while κ usually affects the scattering only slightly. This characteristic implies that singlet-dominated particles may form a secluded DM sector. Under such a theoretical structure, the DM achieves the correct abundance by annihilating into a pair of singlet-dominated Higgs bosons by adjusting κ’s value. Its scattering with nucleons is suppressed when λv/μtot is small. This speculation is verified by sophisticated scanning of the theory’s parameter space with various experiment constraints considered. In addition, the Bayesian evidence of the general NMSSM and that of Z3-NMSSM is computed. It is found that, at the cost of introducing one additional parameter, the former is approximately 3.3 × 103 times the latter. This result corresponds to Jeffrey’s scale of 8.05 and implies that the considered experiments strongly prefer the general NMSSM to the Z3-NMSSM.

A fully differential SMEFT analysis of the golden channel using the method of moments

The Method of Moments is a powerful framework to disentangle the relative contributions of amplitudes of a specific process to its various phase space regions. We apply this method to carry out a fully differential analysis of the Higgs decay channel h → 4ℓ and constrain gauge-Higgs coupling modifications parametrised by dimension-six effective operators. We find that this analysis approach provides very good constraints and minimises degeneracies in the parameter space of the effective theory. By combining the decay h → 4ℓ with Higgs-associated production processes, Wh and Zh, we obtain the strongest reported bounds on anomalous gauge-Higgs couplings.

Refinements of the bottom and strange MSSM Higgs Yukawa couplings at NNLO

We extend the already existing two-loop calculation of the effective bottom-Yukawa coupling in the MSSM. In addition to the resummation of the dominant corrections for large values of tg$$\beta $$ β , we include the subleading terms related to the trilinear Higgs coupling $$A_b$$ A b and contributions induced by the electroweak gauge couplings. This calculation has been extended to the NNLO corrections to the MSSM strange-Yukawa coupling. Our analysis leads to residual theoretical uncertainties of the effective Yukawa couplings at the per-cent level.

Exploring sizable triple Higgs couplings in the 2HDM

An important task at future colliders is the measurement of the triple Higgs coupling. Depending on its size relative to the Standard Model (SM) value, certain collider options result in a higher experimental accuracy. Within the framework of Two Higgs Doublet Models (2HDM) types I and II we investigate the allowed ranges for all triple Higgs couplings involving at least one light, SM-like Higgs boson. We take into account theoretical constraints (unitarity, stability), experimental constraints from direct Higgs-boson searches, measurements of the SM-like Higgs-boson properties, flavor observables and electroweak precision data. We find that the SM-type triple Higgs coupling w.r.t. its SM value, $$\lambda _{hhh}/\lambda _{\mathrm {SM}}$$ λ hhh / λ SM , can range between $$\sim -0.5$$ ∼ - 0.5 and $$\sim 1.5$$ ∼ 1.5 . Depending on which value is realized, the HL-LHC can compete with, or is clearly inferior to the ILC. We find the coupling $$\lambda _{hhH}$$ λ hhH between $$\sim -1.5$$ ∼ - 1.5 and $$\sim 1.5$$ ∼ 1.5 . Triple Higgs couplings involving two heavy Higgs bosons, $$\lambda _{hHH}$$ λ hHH , $$\lambda _{hAA}$$ λ hAA and $$\lambda _{hH^+H^-}$$ λ h H + H - can reach values up to $${{\mathcal {O}}}(10)$$ O ( 10 ) , roughly independent of the 2HDM type. This can lead to potentially strongly enhanced production of two Higgs-bosons at the HL-LHC or high-energy $$e^+e^-$$ e + e - colliders.

Towards the ultimate differential SMEFT analysis

We obtain SMEFT bounds using an approach that utilises the complete multi-dimensional differential information of a process. This approach is based on the fact that at a given EFT order, the full angular distribution in the most important electroweak processes can be expressed as a sum of a fixed number of basis functions. The coefficients of these basis functions — the so-called angular moments — and their energy dependance, thus form an ideal set of experimental observables that encapsulates the complete multi-dimensional differential information of the process. This approach is generic and the observables constructed allow to avoid blind directions in the SMEFT parameter space. While this method is applicable to many of the important electroweak processes, as a first example we study the pp → V(ℓℓ)h(bb) process (V ≡ Z/W±, ℓℓ ≡ ℓ+ℓ−/ℓ±ν), including QCD NLO effects, differentially. We show that using the full differential data in this way plays a crucial role in simultaneously and maximally constraining the different vertex structures of the Higgs coupling to gauge bosons. In particular, our method yields bounds on the $$ {hV}_{\mu \nu}{V}^{\mu \nu},{hV}_{\mu \nu}{\tilde{V}}^{\mu \nu} $$ hV μν V μν , hV μν V ˜ μν and $$ hVff\left( ff\equiv f\overline{f}/f\overline{f}^{\prime}\right) $$ hVff ff ≡ f f ¯ / f f ¯ ′ couplings, stronger than projected bounds reported in any other process. This matrix-element-based method can provide a transparent alternative to complement machine learning techniques that also aim to disentangle correlations in the SMEFT parameter space.