EWPD in the SMEFT to dimension eight

We calculate the $$ \mathcal{O}\left({\left\langle {H}^{\dagger }H\right\rangle}^2/{\Lambda}^4\right) $$ O H † H 2 / Λ 4 corrections to LEP electroweak precision data using the geometric formulation of the Standard Model Effective Field Theory (SMEFT). We report our results in simple-to-use interpolation tables that allow the interpretation of this data set to dimension eight for the first time. We demonstrate the impact of these previously unknown terms in the case of a general analysis in the SMEFT, and also in the cases of two distinct models matched to dimension eight. Neglecting such dimension-eight corrections to LEP observables introduces a theoretical error in SMEFT studies. We report some preliminary studies defining such a theory error, explicitly demonstrating the effect of previously unknown dimension-eight SMEFT corrections on LEP observables.

Dimension-8 operators in the Standard Model Effective Field Theory

We present a complete basis of dimension-8 operators in the Standard Model Effective Field Theory. Attention is paid to operators that vanish in the absence of flavor structure. The 44,807 operators are encoded in 1,031 Lagrangian terms. We also briefly discuss a few aspects of phenomenology involving dimension-8 operators, including light-by-light scattering and electroweak precision data.

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.

Correlation between the decays h0 → γγ/gg in the MSSM with quark flavor violation

We study the loop-induced decays [Formula: see text] and [Formula: see text] in the Minimal Supersymmetric Standard Model (MSSM) with quark flavor violation (QFV), identifying [Formula: see text] with the Higgs boson with a mass of 125 GeV, where [Formula: see text] and [Formula: see text] are photon and gluon, respectively. We perform a MSSM parameter scan and a detailed analysis around a fixed reference point respecting theoretical constraints from vacuum stability conditions and experimental constraints, such as those from [Formula: see text]-meson data and electroweak precision data, as well as recent limits on Supersymmetric (SUSY) particle masses from LHC experiments. We find that (i) the relative deviation of the decay width [Formula: see text] from the Standard Model value, [Formula: see text], can be large and negative, [Formula: see text], (ii) the analogous deviation of [Formula: see text] is strongly correlated, [Formula: see text] for [Formula: see text], (iii) the relative deviation of the width ratio [Formula: see text] from the SM value, [Formula: see text], can be large (up to [Formula: see text]20%), (iv) the deviations can be large due to the up-type squark loop contributions, (v) the SUSY QFV parameters can have a significant effect on these deviations. Such large deviations can be observed at a future [Formula: see text] collider like ILC. Observation of the deviation patterns as shown in this study would favor the MSSM with flavor-violating squark mixings and encourage to perform further studies in this model.