Explore the vast range of titles available.

Abstract We investigate the sensitivity of future high-energy muon colliders to neutral triple gauge couplings (nTGCs) through the process μ + μ − → γν ν ¯ $$ {\\mu}^{+}{\\mu}^{-}\\to \\gamma \\nu \\overline{\\nu} $$ within the Standard Model Effective Field Theory (SMEFT) framework. Extending beyond previous studies, we consider a set of 14 dimension-8 operators, including both Higgs-related and pure gauge structures. By computing the cross sections and performing Monte Carlo simulations at multiple center-of-mass energies (3–30 TeV), we demonstrate that the annihilation process dominates over vector boson fusion (VBF) at TeV scales. We also explore the impact of beam polarization and show that the (– +) polarization enhances sensitivity to several operators. After the study of the event selection strategies, we show that muon colliders can impose stronger expected constraints on nTGCs operators than current LHC bounds, with two of the pure gauge operators yielding the most stringent expected constraints. We also evaluate the contribution of CP-violating pure gauge operators to the electron electric dipole moment (EDM), finding that the expected constraints from muon colliders are stronger than those from EDM measurements.

Abstract We explore the prospects for probing new physics (NP) beyond the Standard Model (SM) at the future lepton colliders through precision measurements of e + e − → f f ¯ $$ f\\overline{f} $$ observables off the Z resonance. We consider the interference between the SM contributions and those arising from the dimension-6 four-fermion effective operators that encode the effects of NP, yielding a linear dependence on the latter. This linear dependence in general increases with the collision energy offset from the Z pole. We consider a variety of asymmetries in order to enhance the NP sensitivity while reducing the experimental systematic and theoretical SM uncertainties: the inclusive above- and below-Z-resonance cross section asymmetry (A σ ) as well as the conventional forward-backward (A FB) and polarization (A pol) asymmetries. Based on the projected statistical uncertainties at the Circular Electron-Positron Collider (CEPC), we find that the measurement of A σ could extend the sensitivity to the NP mass scale by as much as a factor of ~ 7 compared to the present reach obtained with the CERN Large Electron Positron Collider. The projected systematic theoretical SM uncertainties substantially reduce this sensitivity gain. For A FB, the experimental systematic uncertainties has a marginal impact on the gain in NP reach, whereas the SM theoretical uncertainties remain a significant barrier to realizing the full NP sensitivity. Analogous conclusions apply to the CERN Future Circular Collider (FCC-ee) and International Linear Collider (ILC).

Abstract The observed baryon asymmetry of the Universe requires new sources of charge-parity ( CP $$ \\mathcal{CP} $$ ) violation beyond those in the Standard Model. In this work, we investigate CP $$ \\mathcal{CP} $$ -violating effects in the top-Higgs sector using the Standard Model Effective Field Theory (SMEFT) framework. Focusing on top-pair production in association with a Higgs boson and single top-Higgs associated production at the LHC, we study CP $$ \\mathcal{CP} $$ violation in the top-Higgs Yukawa coupling and other Higgs and top interactions entering these processes. By analysing CP $$ \\mathcal{CP} $$ -sensitive differential observables and asymmetries, we provide direct constraints on CP $$ \\mathcal{CP} $$ -violating interactions in the top-Higgs sector. Our analysis demonstrates how combining t t ¯ h $$ t\\overline{t}h $$ and thj production can disentangle the real and imaginary components of the top-Yukawa coupling, offering valuable insights into potential sources of CP $$ \\mathcal{CP} $$ violation. The sensitivity of these observables to SMEFT operators provides model-independent constraints on the parameter space, advancing the search for new physics in the top-Higgs sector.

Abstract An extension of the Standard Model is proposed, where the Higgs field is valued in the complex projective plane CP 2 $$ {\\mathbbm{CP}}^2 $$ , rather than ℂ 2. Its geometry is consistent with U(2) ≃ (SU(2) × U(1))/ℤ 2 electroweak gauge symmetry. The leading terms in the Lagrangian, beyond those of the Standard Model, are much more tightly constrained than in general SMEFTs, and the custodial SO(4) symmetry of the Higgs sector is mildly broken. The predicted tree-level deviations from Standard Model phenomenology depend on a single large mass parameter M. Current experimental data imply that M is a few TeV or larger.

Abstract In this paper we explore pp → W ± (ℓ ± ν)γ to O 1 / Λ 4 $$ \\mathcal{O}\\left(1/{\\Lambda}^4\\right) $$ in the SMEFT expansion. Calculations to this order are necessary to properly capture SMEFT contributions that grow with energy, as the interference between energy-enhanced SMEFT effects at O 1 / Λ 2 $$ \\mathcal{O}\\left(1/{\\Lambda}^2\\right) $$ and the Standard Model is suppressed. We find that there are several dimension eight operators that interfere with the Standard Model and lead to the same energy growth, ~ O E 4 / Λ 4 $$ \\mathcal{O}\\left({E}^4/{\\Lambda}^4\\right) $$ , as dimension six squared. While energy-enhanced SMEFT contributions are a main focus, our calculation includes the complete set of O 1 / Λ 4 $$ \\mathcal{O}\\left(1/{\\Lambda}^4\\right) $$ SMEFT effects consistent with U(3)5 flavor symmetry. Additionally, we include the decay of the W ± → ℓ ± ν, making the calculation actually q ¯ q ′ → ℓ ± νγ $$ \\overline{q}{q}^{\\prime}\\to {\\ell}^{\\pm}\\nu \\gamma $$ . As such, we are able to study the impact of non-resonant SMEFT operators, such as L † σ ¯ μ τ I L Q † σ ¯ ν τ I Q $$ \\left({L}^{\\dagger }{\\overline{\\sigma}}^{\\mu }{\\tau}^IL\\right)\\left({Q}^{\\dagger }{\\overline{\\sigma}}^{\\nu }{\\tau}^IQ\\right) $$ B μν , which contribute to q ¯ q ′ → ℓ ± νγ $$ \\overline{q}{q}^{\\prime}\\to {\\ell}^{\\pm}\\nu \\gamma $$ directly and not to q ¯ q ′ → W ± γ $$ \\overline{q}{q}^{\\prime}\\to {W}^{\\pm}\\gamma $$ . We show several distributions to illustrate the shape differences of the different contributions.

A bstract We present a comprehensive analysis of electroweak, flavor, and collider bounds on the complete set of dimension-six SMEFT operators in the U(2) 5 -symmetric limit. This operator basis provides a consistent framework to describe a wide class of new physics models and, in particular, the motivated class of models where the new degrees of freedom couple mostly to the third generation. By analyzing observables from all three sectors, and consistently including renormalization group evolution, we provide bounds on the effective scale of all 124 U(2) 5 -invariant operators. The relation between flavor-conserving and flavor-violating observables is analyzed taking into account the leading U(2) 5 breaking in the Yukawa sector, which is responsible for heavy-light quark mixing. We show that under simple, motivated, and non-tuned hypotheses for the parametric size of the Wilson coefficients at the high scale, all present bounds are consistent with an effective scale as low as 1.5 TeV. We also show that a future circular e + e − collider program such as FCC-ee would push most of these bounds by an order of magnitude. This would rule out or provide clear evidence for a wide class of compelling new physics models that are fully compatible with present data.

Abstract We use the Fitmaker tool to incorporate the recent CDF measurement of m W in a global fit to electroweak, Higgs, and diboson data in the Standard Model Effective Field Theory (SMEFT) including dimension-6 operators at linear order. We find that including any one of the SMEFT operators O $$ \\mathcal{O} $$ HWB , O $$ \\mathcal{O} $$ HD , O $$ \\mathcal{O} $$ ℓℓ or O H ℓ 3 $$ {\\mathcal{O}}_{H\\ell}^{(3)} $$ with a non-zero coefficient could provide a better fit than the Standard Model, with the strongest pull for O $$ \\mathcal{O} $$ HD and no tension with other electroweak precision data. We then analyse which tree-level single-field extensions of the Standard Model could generate such operator coefficients with the appropriate sign, and discuss the masses and couplings of these fields that best fit the CDF measurement and other data. In particular, the global fit favours either a singlet Z′ vector boson, a scalar electroweak triplet with zero hypercharge, or a vector electroweak triplet with unit hypercharge, followed by a singlet heavy neutral lepton, all with masses in the multi-TeV range for unit coupling.

A bstract Rare b hadron decays are considered excellent probes of new semileptonic four-fermion interactions of microscopic origin. However, the same interactions also correct the high-mass Drell-Yan tails. In this work, we revisit the first statement in the context of this complementarity and chart the space of short-distance new physics that could show up in rare b decays. We analyze the latest b → qℓ + ℓ − measurements, where q = d or s and ℓ = e or μ , including the most recent LHCb R K ∗ update, together with the latest charged and neutral current high-mass Drell-Yan data, pp → ℓν and pp → ℓ + ℓ − . We implement a sophisticated interpretation pipeline within the flavio framework, allowing us to investigate the multidimensional SMEFT parameter space thoroughly and efficiently. To showcase the new functionalities of flavio, we construct several explicit models featuring either a Z ′ or a leptoquark, which can explain the tension in b → sμ + μ − angular distributions and branching fractions while predicting lepton flavor universality (LFU) ratios to be SM-like, R K ∗ ≈ R K ∗ SM , as indicated by the recent data. Those models are then confronted against the global likelihood, including the high-mass Drell-Yan, either finding tensions or compatibility.

Abstract We consider associated Zh production with Z → ℓ + ℓ − and h → b b ¯ $$ h\\to b\\overline{b} $$ decays in hadronic collisions. In the framework of the Standard Model effective field theory (SMEFT) we calculate the QCD corrections to this process and achieve next-to-next-to-leading order plus parton shower (NNLO+PS) accuracy using the MiNNLOPS method. This precision is obtained for a subset of six SMEFT operators, including the corrections from effective Yukawa- and chromomagnetic dipole-type interactions. Missing higher-order QCD effects associated with the considered dimension-six operators are estimated to have a relative numerical impact of less than a percent on the total rate once existing experimental limits on the relevant Wilson coefficients are taken into account. We provide a dedicated Monte Carlo (MC) code that evaluates the NNLO SMEFT corrections on-the-fly in the event generation. This MC generator is used to study the numerical impact of NNLO+PS corrections on the kinematic distributions in pp → Zh → ℓ + ℓ − b b ¯ $$ pp\\to Zh\\to {\\mathrm{\\ell}}^{+}{\\mathrm{\\ell}}^{-}b\\overline{b} $$ production employing simple SMEFT benchmark scenarios. We identify the invariant mass m b b ¯ $$ {m}_{b\\overline{b}} $$ of the two b-tagged jets as well as the three-invariant jet mass m b b ¯ j $$ {m}_{b\\overline{b}j} $$ as particularly interesting observables to study SMEFT effects. These distributions receive contributions that change both their normalisation and shape with the latter modifications depending on the exact jet definition. To our knowledge SMEFT effects of this type have so far not been discussed in the literature. The presented MC generator can also serve as a starting point to obtain NNLO+PS accuracy for a suitable enlarged set of effective operators in the future.

A bstract We present SMEF i T3.0, an updated global SMEFT analysis of Higgs, top quark, and diboson production data from the LHC complemented by electroweak precision observables (EWPOs) from LEP and SLD. We consider recent inclusive and differential measurements from the LHC Run II, alongside with a novel implementation of the EWPOs based on independent calculations of the relevant EFT contributions. We estimate the impact of HL-LHC measurements on the SMEFT parameter space when added on top of SMEF i T3.0, through dedicated projections extrapolating from Run II data. We quantify the significant constraints that measurements from two proposed high-energy circular e + e − colliders, the FCC-ee and the CEPC, would impose on both the SMEFT parameter space and on representative UV-complete models. Our analysis considers projections for the FCC-ee and the CEPC based on the latest running scenarios and includes Z -pole EWPOs, fermion-pair, Higgs, diboson, and top quark production, using optimal observables for both the W + W − and the t t ¯ channels. The framework presented in this work may be extended to other future colliders and running scenarios, providing timely input to ongoing studies towards future high-energy particle physics facilities.