Higgs and Effective Field Theory - HEFT 2026

8 Jun 2026, 09:00 → 12 Jun 2026, 14:00 Europe/Madrid

Jardí Botànic, Valencia

Ajdin Palavric (University of Basel), Ana Rosario Cueto Gomez (Universidad Autonoma de Madrid (ES)), Benjamin Stefanek (IFIC Valencia), Javier Fuentes-Martin (Universidad de Granada), Javier Virto (Universitat de Barcelona), Luca Mantani (IFIC, Valencia), Marco Ardu, Maria Moreno Llacer (Univ. of Valencia and CSIC (ES)), Suraj Prakash (IFIC (UV-CSIC)), Víctor Miralles (University of Manchester)

HEFT is an annual workshop focusing on the use of effective field theories to search for physics beyond the Standard Model. A broad range of topics are encouraged, ranging from collider phenomenology and formal aspects to the latest experimental updates on dedicated searches. The meeting aims to foster discussions between theorists and phenomenologists from varied backgrounds as well as with experimental colleagues.

The conference fee of 160 euros covers the coffee-breaks and the conference dinner.

Confirmed speakers:

• Fabio Maltoni
• Lukas Born
• Peter Stoffer
• Alejo Rossia
• Joe Davighi
• Jasper Roosmale Nepveu
• Pablo Olgoso
• Ramona Grober
• Raquel Gomez Ambrosio
• Admir Greljo
• Adam Falkowski
• Mikael Chala
• Upalaparna Banerjee
• Jorge de Blas
• Aleks Smolkovic
• Baptiste Ravina
• Andrea Visibile
• Clara Del Pio

 

Monday 8 June

Registration

Opening session

Renormalisation

1 NLO Running in the SMEFT: Implications of the Two-Loop ADM

The Standard Model Effective Field Theory (SMEFT) provides a systematic framework for parameterizing heavy new physics in a model-independent way. A central ingredient for precision analyses within this framework is the renormalization group equations (RGEs), governing the running of the Wilson coefficients across energy scales. The recent computation of the two-loop $\beta$-functions in the SMEFT marks a milestone in this program, opening the door to genuine next-to-leading order (NLO) analyses.

In this talk, I will first discuss the key technical challenges we encountered in our calculation, how we addressed them by modifying the Warsaw basis, and the consistency checks on our results. Second, I will turn to a concrete phenomenological application, demonstrating that NLO running effects play an important role in Electroweak Precision Observables (EWPO). This example illustrates that the two-loop running can have tangible consequences for the interpretation of precision data.

Speaker: Lukas Born

2 Curiosities in the Renormalization Group for EFTs

Recent works have observed spurious divergences in the RG functions of several EFTs. I will show the origin of these divergences and how they can be addressed by including non-minimal source counterterms. Some of the divergences are related to ambiguities introduced by the presence of flavor. I will give an account of how the redundancies in the EFT basis give rise to additional, unphysical RG ambiguities that have to be accounted for when, e.g., comparing RG functions obtained through different calculations.

Speaker: Anders Eller Thomsen (University of Bern)

3 EFT meets CFT: Operators with large number of fields

Anomalous dimensions of composite operators determine the running of the corresponding couplings in a general QFT/EFT. They also provide a perturbative estimate of the spectrum of interacting conformal field theories (CFTs) at fixed-points of the RG flow. The latter application motivates the computation of anomalous dimensions of composite operators with growing number of field and derivative insertions, transforming in arbitrary representation of global and Lorentz symmetry. I will explain the relevance of these results in CFT, and how this computation can be executed at multi-loop order using the primary basis (suitable for both EFT and CFT applications) and the background field method.

Speaker: Johan Henriksson (CERN)

4 Renormalize SMEFT to Dimension Eight with EFT Tools

We compute the one-loop running of dimension-eight two-fermion operators induced by pairs of dimension-six terms and dimension-eight terms in the Standard Model Effective Field Theory (SMEFT). The calculation is performed off shell, for which we obtain and provide a new and explicitly Hermitian basis of dimension-eight Green’s functions. The analysis involves a large set of redundant operators, introducing significant technical complexity and making the computation error-prone. We overcome the difficulty by utilizing various SMEFT tools, including MatchMakerEFT, mosca and ABC4EFT. All our results can be accessed at github.com/SMEFTDimension8-RGEs.

Speaker: Zhe Ren (University of Granada)

Coffee break

Future colliders

5 Effective Field Theories at Future Colliders - Studies for the 2026 European Strategy Update

Speaker: Jorge de Blas (Universidad de Granada (ES))

6 How large can lepton mixing be?

We show that, contrary to common expectations, the observed charged leptons can have a substantial mixing with new heavier fermions, at the level of 20$\%$.
This can happen, in the language of effective theories, when the effect of mixing with heavier fermions vanishes at tree level in operators of mass-dimension 6 (or it is suppressed by the small charged lepton masses), a cancellation that can be naturally ensured by symmetries.
Using a model that realizes this scenario we consider all current direct and indirect constraints and show that experimental constraints on the mixing are so mild that, given the current direct limit on the mass of the heavy fermions, theoretical considerations become the leading current constraints on the mixing. We also estimate the sensitivity to the mixing at future experiments, including the high-luminosity phase of the LHC and, most notably, the FCC-ee, and FCC-hh. We find a pattern in which the reach of direct searches in hadron machines makes theoretical considerations lead the limits while the precision of lepton machines can beat these theoretical considerations. We find that the FCC can finally reach \textit{per mille} precision in the mixing squared of the charged leptons.

Speaker: CHIARA GIULIANO - (Universidad de Granada)

7 Probing the τ lepton dipole moments at future colliders

The electric and magnetic dipole moments of the electron and muon provide stringent tests of the Standard Model and sensitive probes of new physics. In contrast, the corresponding dipole moments of the tau lepton, well motivated in scenarios with enhanced couplings to third-generation fermions, remain weakly constrained. In our work, we investigate the potential to probe the tau dipole moments at future lepton colliders, focusing on the $e^+e^-$ Future Circular Collider and a high-energy muon collider. We perform a broad analysis on the expected sensitivity on the tau dipole moments that can be reached at such facilities. In order to do so, we consider several different processes, including $\ell^+\ell^- \to \tau^+\tau^-$ ($\ell=e,\mu$), photon-photon collisions $\gamma\gamma \to \tau^+\tau^-$, radiative Higgs decays $H \to \tau^+\tau^-\gamma$, associated Higgs production $\mu^+\mu^- \to \tau^+\tau^- H$, and vector-boson scatterings $\mu^+\mu^- \to \mu^+\mu^-\tau^+\tau^-(H)$, $\mu^+\mu^- \to \bar{\nu}\nu\tau^+\tau^-(H)$, and $\mu^+\mu^- \to \mu\nu\tau\nu\,(H)$. In this talk I will discuss how these channels can be employed to extend the existing bounds by several orders of magnitude.

Speaker: Gabriele Levati

8 Global Fits at Future Colliders with the SMEFiT Framework

In the context of the European Strategy, we present projections for the new physics reach of future high-energy colliders using the latest version of the SMEFiT framework, with a focus on near-term electron-positron colliders (FCC-ee, LEP3 and LCF). We quantify their sensitivity to the SMEFT parameter space in a global analysis while accounting for renormalization group evolution effects and NLO corrections to the EFT cross-sections. We also assess the impact of different theory uncertainty scenarios, and consider a couple of representative UV models. The results of the global analysis are presented in terms of bounds on Wilson coefficients and effective couplings, providing a detailed picture of the potential of these colliders to probe physics beyond the Standard Model.

Speaker: Jaco ter Hoeve (The University of Edinburgh)

9 The SMEFT as a New Physics Microscope at the FCC-ee

The unprecedented precision expected at the FCC-ee offers unique chances to unveil sought-for New Physics signals. However these "BSM searches" will be very different from current searches at LHC, since signals will appear as subtle deviations between ultra-precise data and theory predictions. A blind applications of the global SMEFT fit is unlikely to be able to resolve these signals due to the large dimensionality of its parameter space. In this contribution we study under which conditions the SMEFT framework at the FCC-ee can identify (and not merely constrain/exclude) BSM signals, taking specific UV completions as a case study. A crucial ingredient is the "BSM closure test", where synthetic data corresponding to different UV completions over a wide parameter space is generated (and reproduced by the fit). We also discuss how very low-energy measurements, in particular Beta decays, can be best deployed to complement this exciting program of BSM searches at the FCC-ee.

Speaker: Juan Rojo Chacon (Nikhef National institute for subatomic physics (NL))

Tuesday 9 June

Thermal EFT

10 The high-temperature limit of the SM(EFT)

Speaker: Mikael Chala (Universidad de Granada)

11 Hot news on the phase structure of the SMEFT

We perform dimensional reduction of the dimension-six SMEFT to order $g^4$ in coupling constants $g$. This analysis includes one-loop contributions to kinetic terms and quartic couplings; as well as two-loop contributions, where operators such as four-fermion interactions first appear, to squared mass terms. Using lattice data, we provide evidence that, in contrast with previous statements in the literature, the SMEFT may undergo a first-order phase transition even for null $|\phi|^6$ at zero temperature, where $\phi$ is the Higgs doublet, opening the the door to entirely unexplored directions in model building. In such case, however, our analysis implies that the phase transition is not sufficiently strong, narrowing down the new physics that allows for electroweak baryogenesis.

Speaker: Maria Cristina Fiore (Universidad de Granada)

12 Thermal Scalar QED: Finite-Temperature Effective Action and Phase Transition via the Heat-Kernel

We develop a Heat-kernel based formalism to compute the one-loop thermal effective action relevant for dimensionally reduced 3D Thermal EFT matching. Using this framework, we derive the effective operator basis up to dimension six for the Abelian Higgs model, incorporating the non-perturbative effects of the Polyakov loop, which plays a crucial role in shaping the thermal potential. We discuss the broader implications of these thermal effective operators for physical processes, including the nature of cosmological phase transitions and the resulting gravitational wave spectrum.

Speaker: Mr Debmalya Dey (IIT Kanpur)

13 Matchete meets Dimensional Reduction

Dimensional reduction is a key tool for computing the electroweak phase transition in scenarios beyond the Standard Model. Achieving high precision in this framework requires the systematic inclusion of higher-dimensional operators in an EFT approach, a task that rapidly becomes technically challenging.

In this work, we show that functional methods provide a highly efficient and scalable framework to extend dimensional reduction to higher orders in the operator expansion. Building on this approach, we develop "Matchotter": a fully automated tool that performs the matching procedure with minimal human intervention, effectively reducing a highly non-trivial calculation to the click of a button.

Speaker: Mr ADRIÁN Moreno Sánchez (Universidad de Granada)

14 Symmetry-Based Construction of Heavy-Light Meson EFT: Hilbert Series, Sum Rules, and Finite-Temperature Effects

We develop a unified, symmetry-based effective field theory (EFT) framework for heavy-light meson systems, combining Hilbert series methods, flavor symmetries, and chiral EFT ideas, with a systematic extension to finite-temperature environments.

We construct a complete and non-redundant operator basis for heavy-light meson EFT using Hilbert series techniques, incorporating symmetry constraints, spurions, and redundancy removal through equations of motion and integration-by-parts. Building on this, we derive all symmetry-driven amplitude relations (sum rules) arising from isospin, U-spin, and SU(3)$_V$ flavor symmetries, together with their controlled breaking patterns.

We further extend the framework by incorporating vector mesons within the heavy hadron chiral perturbation theory (HHChPT) framework, combined with heavy meson EFT, enabling a more complete description of heavy–light hadronic dynamics beyond the pseudoscalar sector.

In parallel, we formulate a Hilbert series framework for finite-temperature EFTs on $\mathbb{R}^3 \times S^1$, where reduced symmetry and distinct temporal and spatial structures lead to modified redundancy conditions and new operator building blocks. Using this, we obtain complete operator bases for the Standard Model and selected beyond-the-Standard-Model scenarios at finite temperature, including operators that vanish in the zero-temperature limit. We finally extend this construction to heavy-light meson EFT, providing the first systematic classification of thermal operators in such systems.

This work delivers a coherent EFT toolchain linking operator-basis construction, symmetry relations, and finite-temperature effects, with applications to flavor physics and hot QCD environments.

Speaker: Siddhartha Karmakar

Coffee break

Global EFT

15 TBD

Speaker: Alejo Nahuel Rossia (University of Padua and INFN Sezione di Padova)

16 Understanding the Interplay of PDFs and BSM Effects

Indirect searches for new physics increasingly rely on precise theoretical predictions in the high-energy tails, with Parton Distribution Functions (PDFs) being one of the main bottlenecks.

In this talk, I explore the interplay between the fits of Standard Model Effective Field Theory (SMEFT) Wilson coefficients and PDFs in two key sectors at the LHC, the Drell-Yan and the top sector. I explore two complementary strategies for robust new physics searches: (i) fitting the PDFs and SMEFT parameters simultaneously, and (ii) fitting them separately with a “conservative” determination of the PDFs, using only observables that can safely be considered SM–like. I compare both methodologies in controlled closure tests in a realistic High-Luminosity LHC (HL-LHC) scenario and propose best-practice recommendations for robust indirect new physics searches in the Drell-Yan and top sectors at hadron colliders.

I extend this with the inclusion of low-energy using the CLEW (Collider, Low energy and Electroweak precision) framework to perform a global SMEFT+PDF fit free from flavour assumptions. This demonstrates the impact of low-energy data in improving constraints and lifting degeneracies within SMEFT fits.

Speaker: Ella Cole (DAMTP, University of Cambridge)

17 Global SMEFT analyses and the role of Higgs measurements

We present constraints on dimension-6 Standard Model Effective Field Theory (SMEFT) operators from a global fit to electroweak, Drell-Yan, Higgs-boson, top-quark, and flavour observables. The analysis is performed under different flavour symmetry assumptions, including $U(3)^5$ and $U(2)^5$, and considers both global and single-coefficient fits. The scale dependence of the Wilson coefficients is consistently included via renormalization group evolution from the ultraviolet to low-energy scales. We discuss the complementarity of observables, highlighting the growing impact of Higgs precision measurements in probing New Physics.

Speaker: Mauro Valli (INFN Rome)

18 The SMEFT way to New Physics

SMEFT is a powerful framework to explore imprint of New Physics when the mass of the new states is out of experimental reach. In recent years, significant effort has been devoted to performing global fits in order to correlate deviations observed across different measurements. However, the large dimensionality of the parameter space can limit the sensitivity of this approach and obfuscate the identification of potential signals. In this talk, I will discuss how to move beyond traditional global fits by adopting a Bayesian model selection framework combined with genetic algorithms, enabling a more effective detection of deviations from the SM and a more accurate characterization of the underlying new physics scenario in the context of future lepton colliders.

Speaker: Simone Tentori (UCLouvain)

13:00 Lunch

Flavour

19 Minimal Flavor Protection in the SMEFT

Speaker: Admir Greljo (Universitaet Basel (CH))

20 What can flavour tell us about Dark Matter?

The non-trivial flavour structure of t-channel dark matter models with fermion couplings is unavoidably constrained by flavour physics, hinting towards the presence of an underlying flavour symmetry.
In this talk, I present a systematic study of the low-energy flavour constraints affecting these models from the perspective of flavour symmetries, together with complementary bounds from collider searches and dark matter direct detection experiments.
I show that the TeV scale suggested by the freeze-out mechanism is compatible with the various probes only in specific flavour-symmetric limits, highlighting the essential role of flavour symmetries in the realisation of these models.

Speaker: Xavier Ponce Diaz (University of Basel)

21 Implications of Flavor Symmetries for Baryon Number Violation

In the Standard Model, baryon number is an accidental symmetry, whose violation would constitute unambiguous evidence of new physics, with proton decay providing its most prominent experimental signature. At the same time, the peculiar structure of flavor can serve as a guiding principle for exploring possible new-physics effects. In this talk, I present a systematic classification of dimension-six baryon-number-violating (BNV) SMEFT operators across several flavor-symmetry assumptions and analyze the resulting phenomenology. Interestingly, in certain flavor scenarios the non-trivial interplay with tiny neutrino masses leads to proton-decay constraints compatible with BNV scales in the multi-TeV range. Finally, I will complement the EFT analysis by identifying one-particle UV completions of the BNV operators, revealing scenarios in which the leading-order EFT description may not fully account for their underlying dynamics.

Speaker: Arnau Bas I Beneito (Universitat de València (UV, IFIC))

22 Pion $\beta$ decay and $\tau \rightarrow \pi \, \pi \, \nu_{\tau}$ beyond leading logarithms

Semi-leptonic processes involving pions are used to test the Standard Model at high precision. On the theory side, the evaluation of radiative corrections is a crucial ingredient for a robust comparison between theoretical predictions and experimental measurements. In this talk, I will present the first complete effective field theory treatment of radiative corrections in pion $\beta$ decay ($\pi^{\pm} \rightarrow \pi^0 \, e \, \nu_{e}$) and $\tau^{\pm} \rightarrow \pi^{\pm} \, \pi^{0} \, \nu_{\tau}$, including the matching to Chiral Perturbation Theory, beyond leading-logarithmic accuracy. As main applications, I will first show how the theoretical uncertainty for the SM prediction of $V_{ud}$ based on pion $\beta$ decay is reduced by a factor of three, making it negligible even beyond the reach of the PIONEER experiment. Second, I will present an evaluation of isospin-breaking corrections to $\tau \rightarrow \pi \pi \nu_{\tau}$ with negligible uncertainty from the short-distance matching, as necessary for a future $\tau$-based determination of the hadronic-vacuum-polarization contribution to the anomalous magnetic moment of the muon.

Speaker: Nicola Valori - (University of Valencia & IFIC)

Coffee break

Renormalisation

23 EFTs and the gradient flow beyond leading log

Speaker: Peter Stoffer

24 Top-to-Down NLL EFT Analysis: Pheno Implications and Scale Dependence

After much effort from several groups in the EFT community, most of the two-loop Renormalization Group equations are now known in both the SMEFT and the LEFT. In this project, we have implemented them into the Mathematica package DsixTools, and numerically solved them consistently to NLL precision, together with the already well-known one-loop SMEFT-LEFT matching, in order to generate a NLL-evolution matrix extending all the way from the NP scale in the SMEFT down to the low-energy scales in the LEFT. We have then studied the implications of this NLL matrix both in terms of its phenomenological impact and its scale dependence.

Speaker: Pol Morell Ferrer (Universitat de Barcelona)

25 Symmetry-restoring finite counterterms of SMEFT four-fermion operator insertions at one-loop

Dimensional regularization is nowadays the most used technique to perform loop calculations in Quantum Field Theories. However, it faces some complications when applied to chiral gauge theories such as the Standard Model of particle physics because it is not possible to define a mathematically consistent D-dimensional scheme that preserves gauge symmetries. Nonetheless, for a theory free of physical anomalies it is always possible to restore the symmetry by the addition of the appropriate set of both infinite and finite counterterms. In our work, we present the complete calculation of such finite counterterms needed for the consistent renormalization of the dimension six four-fermion operators of the Standard Model Effective Field Theory at one loop using the Breitenlohner-Maison-’t Hooft-Veltman scheme.

Speaker: Sergio Ferrando Solera

26 Mapping between $\gamma_5$ schemes in the Standard Model Effective Field Theory

In this talk I will present the relation between two distinct prescriptions for $\gamma_5$ in dimensional regularization – the Breitenlohner Maison t’Hooft Veltman (BMHV) scheme and Naive Dimensional Regularisation (NDR) in the SMEFT.
I will show how the quantum effective action can be translated between both schemes and present these translation rules for the Wilson Coefficients. I will conclude presenting a practical example of the map, namely the two-loop contributions from four-fermion operators to the running of $m_t,g_s$.

Speaker: Stefano Di Noi (KIT (ITP))

27 Two-Loop Renormalization of Chiral SU(N) Gauge Theories: Toward a Systematic Extension to Effective Field Theories

We revisit the renormalization of generic non-Abelian gauge theories of SU(N) type in the presence of γ₅ within the BMHV scheme. Using algebraic renormalization, we derive the complete structure of one- and two-loop counterterms, including evanescent contributions arising from the non-anticommuting γ₅, and explicitly construct the finite counterterms required to restore BRST symmetry.

As a central outcome, we wish to formulate a general strategy to extend these techniques beyond renormalizable theories. In particular, we outline how the BMHV framework can be systematically applied to effective field theories (EFTs), where higher-dimensional operators and operator mixing amplify the role of evanescent structures and finite counterterms.

Speaker: Vera Paroutiadou (ETH Zurich)

Wednesday 10 June

Geometry, Positivity and Amplitudes

28 The Bundle Geometry of Quantum Field Theories

Speaker: Joe Davighi (University of Cambridge (GB))

29 A Shortcut to SMEFT Amplitudes using EFT Geometry

Effective Field Theories (EFTs) are a framework to probe physics beyond the Standard Model (BSM) in a model independent way. The Standard Model Effective Theory (SMEFT) provides an expansion of higher-dimensional operators that encode the effects of heavy new physics; however, in the operator basis there exists a redundancy in the space of field redefinitions which leaves on-shell amplitudes invariant. A geometric formulation of the SMEFT reframes the language of an arbitrary operator-basis approach to clearly represent fields as coordinates and field redefinitions as coordinate transformations. This geometric viewpoint motivates the adoption of Riemann Normal Coordinates (RNC) to remove spurious kinematic pole structures. Implementing the global symmetry in the RNC basis enables an all-order expansion of the field space metric and associated operators, providing a covariant description of N-point off-shell scattering amplitudes in the high energy limit around the vacuum expectation value (vev). Such a geometric perspective can aid in the systematic analysis of collider data for future BSM searches by highlighting observable signatures of new physics.

Speaker: Cristofer Caballeros

30 Unitarity bounds and sum rules in the SMEFT

We present a comprehensive reassessment of perturbative unitarity bounds in the dimension-six Standard Model Effective Field Theory, exploiting a new formalism based on spinor-helicity techniques to derive partial-wave unitarity bounds for generic $N \to M$ scattering amplitudes. We find that, in several cases, these theoretical constraints are already competitive with, or even stronger than, the corresponding experimental bounds for energy scales above a few TeV. This is especially the case for four-fermion operators under realistic flavor assumptions, where unitarity bounds can be further strengthened by exploiting sum rules. These results provide a valuable and timely contribution towards the ambitious program of new-physics searches with minimal theoretical priors supplemented by restrictive, yet general, first-principles criteria.

Speaker: Andrea Sainaghi (University of Padua)

31 Progress in the Universal SMEFT

I will discuss recent work in developing the Universal SMEFT approach, this will hopefully include two forthcoming papers:
1) The relevance of dimension-eight terms in Drell Yan from comparing the top-down and bottom-up approaches.
2) The geometry of the Universal SMEFT and its breaking pattern at one-loop.

Speaker: Tyler Corbett (University of Vienna)

32 Multi boson processes in EFTs via on-shell methods

Multi-boson processes are a valuable tool for deepening our understanding of the dynamics of the Higgs boson. In this talk we evaluate if they can be used to shed some light on the question of its transformation under the Standard Model symmetry group. To address this we resort to the application of on-shell amplitude methods to processes involving massive vectors and scalars. We construct the relevant kinematic structures for each case, match the results to both HEFT and SMEFT and analyze the differences between them in search of measurable phenomenological effects. The talk here presented is based on ongoing work that extends the results published in [2509.02680] for gluon fusion by my collaborators.

Speaker: Clara Hernández García (Universidad de Granada)

Coffee break

Top, Higgs and EW

33 To HEFT or to SMEFT? Multi-Higgs production as a probe of electroweak symmetry breaking

Speaker: Ramona Grober (Università di Padova and INFN, Sezione di Padova)

34 Could electron-top interactions spoil the measurement of the Higgs trilinear?

The measurement of the Higgs self-coupling is considered the next milestone in the study of the Higgs boson properties.
At future $e^+e^-$ facilities below the double Higgs production threshold, this is extracted from the $Zh$ production cross-section, which is sensitive to the trilinear coupling at the one-loop level.
At the same perturbative order, potential effects beyond the Standard Model (SM) may affect the Higgstrahlung rate and distort the self-coupling determination.
We study the question focusing especially on contact interactions containing two electron and two top-quark fields.
We conclude that, in the context of FCC-ee and its planned runs at different energies, $eett$ interactions change the Higgs self-coupling sensitivity below the percent level. Even in the most pessimistic scenarios, we confirm a robust sensitivity of the order of 17\% at the 1$\sigma$ confidence level under the assumption of otherwise SM-like Higgs couplings. A crucial role in these results is played by the measurement of fermion pair production above the $Z$ resonance.

Speaker: Lucine Tabatt

35 Differential observables for the Higgs-strahlung process to all orders in EFT

We develop methods to obtain the fully differential cross-section for the $f \bar{f} \to Z(\ell\ell)\,h$ process to any desired order in effective field theory (EFT). To achieve this, we first derive a mapping between the partial wave expansion and the EFT expansion to all orders. We find that at lower orders, EFT predicts correlations between the different partial wave coefficients. This allows us to construct linear combinations of partial wave coefficients that get their leading contributions from a higher dimension EFT operator. We then introduce experimental observables, the so called angular moments $-$ that probe these linear combinations of partial wave coefficients$-$and can be determined from a fully differential analysis of the angular distribution of the leptons arising from the $Z$ decay. We show that analysing the dependence of these angular moments on the $Zh$ invariant mass allows us to systematically probe all higher dimension EFT operators contributing to this process. In particular, we discuss how our results can be used to probe dimension-8 operators in the Standard Model EFT (SMEFT). While we take the Higgs-strahlung process as an example, the methods developed here are completely general and can also be applied to other 2-to-2 collider processes.

Speaker: Mr Sourav Bera (Tata Institute of Fundamental Research, Mumbai)

36 Partial-wave unitarity bounds on CP-odd dimension-eight anomalous quartic gauge couplings in SMEFT

We derive partial-wave unitarity constraints on CP-odd operators in the Standard Model Effective Field Theory (SMEFT) that generate genuine anomalous quartic gauge couplings. We consider the complete set of twelve independent dimension-eight CP-odd operators, comprising six mixed field-strength structures and six tensor operators built from dual field strengths.
We analyze two-to-two scattering of electroweak gauge bosons and Higgs bosons, including all coupled channels and helicity amplitudes contributing to the $J=0$ and $J=1$ partial waves. The corresponding coupled-channel scattering matrices are constructed and diagonalized in the multidimensional space of Wilson coefficients to extract perturbative unitarity bounds. We present the complete set of constraints, systematically exploring all relevant combinations of simultaneously switched-on CP-odd operators and quantifying the impact of their interplay on the resulting bounds.

Speaker: Samuel Rosende Herrero (IFT UAM-CSIC)

13:00 Lunch

HEFT

37 TBD

Speaker: Raquel Gomez Ambrosio

38 HEFT-FR - FeynRules implementation of the Higgs Effective Field Theory

HEFT-FR is a FeynRules implementation of the Higgs Effective Field Theory (HEFT), designed to facilitate the inclusion of next-to-leading order (NLO) operators in experimental and phenomenological analyses. The model incorporates physical input schemes for the electroweak sector, a consistent power counting prescription, and allows users to select custom subsets of Wilson coefficients for focused studies. With its ability to export to UFO and FeynArts formats, HEFT-FR offers a flexible and efficient framework for both theoretical and experimental research in high-energy physic focused on HEFT. The code is currently under active development and is expected to be publicly released in the near future.

Speaker: Michal Jakub Ryczkowski (Università di Padova and INFN, Sezione di Padova)

39 Multi-boson production and HEFT anomalous couplings

We discuss various aspects of multi-boson (H,W,Z) production from longitudinal electroweak (EW) gauge boson scattering in the TeV region as the necessary information to characterise the Flare function, F(h), which determines whether the Standard Model EFT (SMEFT) or the Higgs EFT (HEFT -also sometimes referred as the EW Chiral Lagrangian-) is the appropriate description. We analyze various correlations among Higgs couplings that help decide, from experimental data, whether we have a viable SMEFT low-energy scenario. We present an EFT study of the scattering into states with one, two, three and four Higgs bosons in the final state, in addition to possible extra EW gauge bosons. We show several important cancellations and simplifications which allows us to display these amplitudes in a very compact form. For a growing number of Higgs bosons in the final state, SMEFT leads to an important suppression of the cross sections with a large number of Higgses, while this does not happen for general HEFT low-energy scenarios (which do not accept a SMEFT description). We provide some numerical estimates of these multi-boson cross sections based on current experimental bounds. Finally, we show how field redefinitions -or an appropriate choice of the scalar manifold coordinates- can provide a more transparent picture of these processes.

Speaker: Juan José Sanz-Cillero (Universidad Complutense de Madrid & IPARCOS)

40 MATCHA: a package for matching UV theories onto HEFT

We present MATCHA (MATChing Heft Amplitudes), a package for leading-order (LO) matching of ultraviolet (UV) theories onto the Higgs Effective Field Theory (HEFT). MATCHA uses amplitude-level matching to extract the low-energy parameters of the effective theory, capturing non-decoupling effects of order $\mathcal{O}(1)$. The package supports arbitrary Higgs multiplicities, allowing for a systematic determination of the series of HEFT couplings governing gauge, scalar, and Yukawa interactions, providing an efficient way to study beyond the standard model effects on HEFT.

Speaker: Carlos Quezada Calonge (Università di Torino)

Coffee break

Matching and general EFTs

41 EFTs, the efficient way

EFTs are an efficient strategy to search for new physics, but the large number of possible models together with a lack of guidance can hinder their efficiency. In this talk, I will review two ways to overcome this problem: calculations in general EFTs that encompass any particular theory and UV-IR dictionaries to readily translate between models and data.

Speaker: Pablo Olgoso Ruiz (University of Padova)

42 Dispersion relations in the dimension-six SMEFT

Dispersion relations connect low-energy EFT amplitudes to UV cross sections, resulting in theoretical constraints on the allowed space of Wilson coefficients. While at dimension eight they result in positivity conditions, at dimension six the indefinite sign of these relations makes it difficult to, a priori, extract useful information. In this work, we show that dispersion relations, when applied to different classes of dimension-six SMEFT operators, can actually map broad classes of UV models to specific signs and structures at tree and one loop levels. This enables the extraction of nontrivial information about the UV theory directly from the sign of an observed deviation. We further consider expected correlations across different flavor entries and among different Wilson coefficients, helping to assemble a consistent picture of the UV from IR observables.

Speaker: Guilherme Guedes

43 Matchete meets UFO

In this talk, we present a new setup for deriving Feynman rules in generic Beyond the Standard Model (BSM) scenarios, including Effective Field Theories (EFTs), based on the Matchete framework. The Feynman rules can be examined analytically or conveniently exported in the Universal Feynman Output (UFO) format, which can then be interpreted by Monte Carlo event generators. The integration of the intuitive model-definition setup and the automatic matching capabilities of Matchete with event generators within this framework enable the streamlining of collider studies of various BSM theories and their low-energy EFT descriptions. To illustrate this point, we present a study of the validity range of the EFT description for a leptoquark search performed by the ATLAS collaboration at the LHC. In addition, we will also address the effort to incorporate higher-order contributions in this framework. In particular, we discuss the automatic determination and inclusion of counterterms required for the computation of one-loop corrections as well as the extension to dimension-eight EFT operators.

Speaker: Felix Wilsch (RWTH Aachen University)

44 Anomalous Dimension of a General Effective Gauge Theory

I will present the classification of physical operators and the derivation of the complete set of one-loop anomalous dimensions for general EFTs up to dimension six, covering both the bosonic and fermionic sectors. Building on this classification, I will discuss the complete set of leading-order renormalization group equations, computed using unitarity-based on-shell techniques. This analysis consistently accounts for renormalization effects at order $1/\Lambda^2$, fully includes operator mixing across different dimensions, and applies broadly to any EFT with arbitrary gauge symmetry containing scalar, vector, and fermion fields.

Speaker: Luigi Carlo Bresciani (University & INFN Padova)

45 From a general EFT to specific operator bases

Recent work on general effective field theories has provided a framework for the classification of operators in EFTs with arbitrary field content and symmetry structure. In this talk, I will discuss how this setup can be turned into a practical tool for constructing explicit operator bases in specific EFTs. The main idea is to start from the general operator classification and then specialize it to a chosen field content and symmetry group, obtaining a basis that is automatically compatible with the general one.

Speaker: Renato Fonseca (University of Granada)

46 Automated Generation of Explicit Operator Bases for Arbitrary EFTs

Effective Field Theories (EFTs) are an indispensable framework for capturing the low-energy effects of heavy new physics. While powerful tools like basisgen use Hilbert series methods to elegantly enumerate the exact number of independent operators at a given mass dimension, constructing their explicit tensor forms remains a highly non-trivial and often manual task. This bottleneck complicates the systematic matching of UV models and the extraction of physical observables. In this talk, I will present ongoing work on a new Python-based computational framework designed as a comprehensive extension to basisgen. Rather than solely calculating operator redundancies, this upgraded tool algorithmically generates the explicit tensor structures required to construct both a complete Green's basis and a minimal physical basis. I will discuss the core methodology of the Python package, demonstrate its application to standard EFTs, and outline its potential by fully automating the basis-generation process up to an arbitrary mass-dimension.

Speaker: JAVIER LÓPEZ MIRAS

Dinner

Thursday 11 June

ALPs

47 Global fit of axion-like particle EFT at the collider frontier

Speaker: UPALAPARNA BANERJEE (JGU Mainz)

48 A Unified SMEFT and ALP Analysis of KSVZ-like Models

We carry out a systematic study of a broad class of UV completions of the Standard Model containing vector-like fermions and a complex scalar responsible for spontaneous PQ-symmetry breaking and the emergence of an axion-like particle (ALP). We classify the viable models and match them onto both SMEFT and ALP effective theories, deriving the corresponding low-energy descriptions for each case. This framework makes it possible to identify the characteristic operator patterns induced by each model and to uncover non-trivial correlations between the two EFT sectors. These correlations allow us to combine both sectors into a unified SMEFT-ALP EFT.We analyze this combined EFT using electroweak precision, Higgs, flavor, and axion constraints, and find that this framework provides a unified strategy to test different well-motivated ultraviolet scenarios.

Speaker: Hector Tiblom

49 Crossing the $m_a > f_a$ frontier in EFTs of leptophilic ALPs

Axion-like particle (ALP) effective field theories (EFTs) provide a powerful, UV-agnostic framework for studying ALP phenomenology. Phenomenological analyses within this framework typically assume that the ALP mass lies well below the decay constant, i.e. $m_a << f_a$, following standard EFT intuition. In this poster, motivated by the analogous situation in chiral perturbation theory - where pseudo-Nambu-Goldstone pions can have masses comparable to the decay constant - we revisit the validity criterion of ALP EFTs. We show that the conventional requirement is overly restrictive and not necessary for a consistent UV-agnostic description. We then present the first dedicated phenomenological study of ALP EFTs in the complementary regime, focusing on the particularly clean case of leptophilic ALPs. Finally, we demonstrate that such a scenario can potentially alleviate the 3.8 $\sigma$ tension in the Caesium determination of the electron magnetic dipole moment.

Speaker: Álvaro Lozano Onrubia (IFT UAM-CSIC)

Global EFT

50 Differentiable EFT likelihoods for BSM phenomenology

Speaker: Aleks Smolkovic (Jozef Stefan Institute)

51 Global Analysis of Linear Standard Model Extensions

Linear Standard Model Extensions (LSMEs) are a motivated set of simplified models for exploring the phenomenology of physics beyond the Standard Model (BSM) and assessing the reach of future colliders. They capture a wide range of BSM physics: any particle coupling linearly to the Standard Model (SM) with relevant or marginal interactions is an LSME. Examples include vector-like fermions, new gauge bosons, strongly coupled composite resonances, $R$-parity-violating supersymmetry, or, more generally, any field whose quantum numbers permit such linear couplings to the SM. The finite possibilities have all been classified. We study the indirect sensitivity of the HL-LHC and FCC-ee future colliders to all LSMEs in a global analysis using the power of the Standard Model Effective Field Theory (SMEFT) framework, incorporating one-loop renormalisation group running and matching effects, to perform a more systematic survey than would otherwise have been feasible without recent SMEFT developments.

Speaker: Victor Maura Breick (King's College London)

Coffee break

Neutrinos

52 New Physics Searches in Nuclear Beta Decay

Speaker: Adam FALKOWSKI

53 Relating Charged and Neutral Lepton Flavor Violation with Effective Field Theory

Many experiments have been conducted to search for charged lepton flavor violation (CLFV) and have yielded very strong constraints. At the same time, there has been much interest in neutrino nonstandard interactions (NSI), which could also in general be flavor-violating. However, the direct constraints on NSI are typically rather weak due to the present limitations of neutrino experiments. As noted previously by various authors, the stronger constraints on CLFV can be used to establish indirect constraints on flavor-violating NSI under certain assumptions about the new physics; in particular, if the new physics takes the form of tree-level, mass-dimension-six effective operators, the $SU(2)_L$ symmetry will establish a close connection between CLFV and flavor-violating NSI. Working in this established paradigm, we seek to update some of these constraints using recent experimental results; we find that for many effective operators, the CLFV places constraints on NSI that would push it beyond the sensitivity of most neutrino experiments, although still at levels of interest to those studying the role of neutrinos in supernovae. We find that some operators, however, are subject only to weaker indirect constraints which are comparable to the direct ones.

Speaker: William McNulty (Indiana University)

54 But what are the odds? UV models for SMEFT dim-9 operators and implications for neutrinoless double beta decay and radiative neutrino masses

The observation of lepton number violation (LNV) would be clear evidence for physics beyond the Standard Model, and non-zero neutrino masses particularly motivate a study of processes that violate lepton number by two units, like e.g. neutrinoless double beta decay.
In the Standard Model Effective Field Theory (SMEFT), $\Delta L =2$ operators appear at dimension-5 and higher odd dimensions.
Focusing on dimension-9 operators, I will present a diagram-based classification of tree-level UV models and isolate minimal two-particle models that avoid generating the dimension-5 operator or dimension-7 LNV operators at tree level.
I then chart how these minimal models populate the operator landscape and organise them by the loop order at which they radiatively induce lower-dimensional LNV operators, highlighting scenarios in which the tree-level dimension-9 contribution can compete with or dominate loop-suppressed neutrino-mass (dimension-5) effects.
For a representative model, I will show the matching onto the SMEFT, its implications for neutrino masses and the relative size of dimension-9 versus dimension-5 contributions to neutrinoless double beta decay.

Speaker: Fabian Esser

55 From DUNE Sensitivities to UV Models: Implications of Flavor Constraints

Future neutrino experiments, in particular DUNE, are expected to probe new physics through their sensitivity to non-standard neutrino interactions (NSIs), i.e. LEFT/WEFT dimension-six Wilson coefficients. We investigate whether such effects can arise from realistic ultraviolet (UV) models. To this purpose we develop a computational pipeline that connects UV scenarios to phenomenological constraints, aiming to maximize a given signal. The framework relies on a set of tools. We perform one-loop matching onto SMEFT operators using SOLD and incorporates global flavor constraints through smelli. Within this setup, we implement an optimization procedure that maximizes a selected Wilson coefficient—representing the target signal—while enforcing consistency with all other constraints. This allows us to determine the maximal size of the effect compatible with existing flavor data and assess whether the EFT sensitivities suggested by neutrino experiments can be realized within viable UV models.

Speaker: Adriano Lana Cherchiglia (Universidade Estadual de Campinas)

13:00 Lunch

Keynote talk

56 Deciphering the quantum fabric of the SM(EFT)

Speaker: Prof. Fabio Maltoni (Universite Catholique de Louvain (UCL) (BE) and Università di Bologna)

Experimental

57 EFT interpretations of ATLAS and CMS top measurements

Speaker: Baptiste Ravina (CERN)

Coffee break

Experimental

58 Global EFT fits in ATLAS and CMS

Speaker: Andrea Visibile (Stockholm University (SE))

59 EFT interpretations and HL-LHC projections of Higgs and diHiggs at ATLAS and CMS

Speaker: Jin Wang (Chinese Academy of Sciences (CN))

Top, Higgs and EW

60 NLO corrections in the SMEFT

Speaker: Clara Lavinia Del Pio (Brookhaven National Lab)

61 Sensitivity to top-quark couplings in diboson production at lepton colliders

I will present results for the next-to-leading order electroweak corrections to $e^+e^-\to W^+W^-$ from dimension-six two-fermion top-quark operators in the SMEFT.
I will discuss the analytical computation and show results for future electron–positron colliders, focusing on the proposed LEP3 and FCC-ee that will operate at centre of mass energies below the $t\bar t$ production threshold.
I will compare the indirect sensitivity arising from virtual corrections to $W^+W^-$ production to that from $ZH$ production, and to the current constraints from LEP and LHC data. Our results show that NLO corrections can provide competitive sensitivity to these operators. This work represents a first step toward the systematic computation of electroweak corrections to $W$-pair production at lepton colliders in the SMEFT.

Speaker: Eugenia Celada

62 A Comprehensive Study of Top-Quark Effective Interactions in the SMEFT Framework

We perform a global analysis of top-quark flavour-changing neutral current (FCNC) interactions and the dominant charged-current $(Wtb)$ coupling within an effective field theory framework, incorporating constraints from low-energy flavour observables, electroweak precision data, Higgs and gauge-boson measurements, and electric dipole moment (EDM) bounds. Beginning with a general parametrisation of the top-quark couplings, we match these interactions to the Standard Model Effective Field Theory (SMEFT) operator basis at the top-quark scale. By treating the top-dipole operators as complex, we derive stringent limits on both the real and imaginary parts of the top FCNC couplings. In addition, the bounds on the charged-current top-quark effective coupling $(Wtb)$ are significantly improved compared to the existing limits reported by ATLAS and CMS. Finally, we provide predictions for branching ratios and CP asymmetries in rare top-quark decays. We identify well-motivated benchmark scenarios for future collider searches and emphasise the crucial role of CP-violating effects in probing the flavour structure of the top quark.

Speaker: Mr Subhajit Kala (Indian Institute of Technology Guwahati)

Friday 12 June

Geometry, Positivity and Amplitudes

63 Positivity in EFT renormalization and the operator product expansion

Speaker: Jasper Roosmale Nepveu (National Taiwan University)

64 Quantum correction to the diffusion term in stochastic inflation from SdSET

Soft de Sitter Effective Theory (SdSET) is a promising candidate for the correct effective description of superhorizon modes of quantum fields in de Sitter spacetime. It is especially valuable for achieving control over theories with strong infrared effects. A prototypical example is the massless, minimally coupled scalar field, whose correlation functions are infrared-divergent in perturbation theory. However, the interacting theory self-regularizes these divergences non-perturbatively by dynamically generating a mass scale, a phenomenon that was first understood within the formalism of stochastic inflation. In the SdSET this formalism emerges as a consequence of operator mixing under renormalization, and the EFT offers the possibility to systematically include higher-order corrections to the Fokker-Planck equation. In this talk, I will introduce the SdSET, show how to renormalize and match composite operators in dimensional regularization to their full-theory counterparts, and demonstrate how the EFT can be used to compute the first quantum correction to the diffusion term.

Speaker: Dr Andrea Federico Sanfilippo (Universidad de Granada)

65 A Covariant Formalism for Scattering Ampltiudes up to 2-Loop Order

Covariant Feynman rules allow for scattering amplitudes to be expressed in manifestly invariant forms under field redefinition. In this talk the derivation of the covariant rules and their validity at the tree, 1-loop and 2-loop level will be demonstrated. Additionally the use of geometric methods to obtain explicit expressions for the covariant rules will be showcased.

Speaker: Mohammad Alminawi

HEFT

66 Theoretical uncertainties in (H)EFT: Equations of Motion vs. Field Redefinitions

Effective field theories rely on truncated expansions whose interpretation is intertwined with redundancies from field redefinitions. This interplay raises important questions about power counting and the consistent assignment of theoretical uncertainties associated with neglected higher-dimensional operators.

In this talk, I use field redefinition invariance as a diagnostic tool to assess truncation effects, contrasting equation of motion substitutions with explicit field redefinitions. I show how this strategy extends familiar methods for estimating theoretical uncertainties in the renormalisable Standard Model to the non-renormalisable framework of effective theories. As a case study in the Higgs Effective Field Theory, I illustrate how universal Higgs modifications interplay with process-dependent sensitivities in realistic observables.

Speaker: Wrishik Naskar (DESY)

67 Updated Lower Bounds on Resonance Masses within HEFT

The LHC has established a clear mass gap between the Standard Model particles and possible new states, making effective field theory the natural framework to search for indirect signals of new physics. We adopt the HEFT, the electroweak effective theory in its nonlinear realization, where the Higgs is treated as a singlet with independent couplings. At higher energies we describe possible heavy bosonic states through a generic resonance Lagrangian. After integrating out these resonances and imposing proper short-distance constraints, the bosonic low-energy constants can be given in terms of resonance masses. Using updated experimental inputs, we have reanalyzed these constraints and find stronger bounds than in our previous studies, pushing the allowed resonance masses higher. This bottom-up approach shows how increasingly precise low-energy data can sharpen our picture of the high-energy dynamics beyond the Standard Model.

Speaker: Ignasi Rosell (Universidad CEU Cardenal Herrera)

68 Di-Higgs Production in HEFT and SMEFT

Higgs pair production offers the opportunity to probe correlations among the couplings of one or two Higgs bosons to fermions and gauge bosons. In this context, it serves as a powerful test of the underlying EFT framework. In this talk, we study Higgs pair production via gluon fusion within the Higgs Effective Field Theory (HEFT) including NLO and NNLO operators. Furthermore, we complement this study by a discussion of the process in the Standard Model Effective Field Theory (SMEFT) up dimension-8 and discuss the associated phenomenology.

Speaker: Konstantin Schmid (University and INFN Padova)

Coffee break

Flavour

69 Flavor hierarchies with nonminimal irreducible representations

We consider a novel class of flavor models where the spurion breaking the flavor symmetries of the Standard Model transforms in a non-minimal irrep. Starting from initial $\mathcal{O}(1)$ untuned entries in the UV, we find that flavor hierarchies can be generated accidentally via multiple insertions of the spurion. By considering non-Abelian symmetries, we show that the pattern of flavor-violating operators at dim-6 SMEFT can be distinct from analogous Abelian mechanisms such as MFV and Froggatt-Nielsen. As an example of the phenomenological difference, we highlight the potential for unsuppressed flavour violation in kaon mixing, motivating a broad experimental programme in the future. This is based on our recent work, arxiv:2510.03403.

Speaker: Graeme Crawford

70 Electroweak precision physics via angular distributions in hadronic τ decays

Semileptonic τ decays mainly proceed via interactions between charged lepton and quark currents. The hadronization of the quark current is intrinsically nonperturbative and generally cannot be addressed analytically. In this work, we propose using symmetry arguments alone to construct clean angular observables that, within the Standard Model and in the absence of long-distance electromagnetic corrections, remain form-factor independent. We study the structure of deviations from the Standard Model predictions within the framework of the Weak Effective Field Theory. This allows us to identify which of our proposed observables constitute genuine precision tests of the SM and which would remain unchanged in the presence of heavy new physics. By delineating robust SM predictions from more general possibilities, our work establishes a set of clean experimental probes with minimal theoretical assumptions.

Speaker: Santiago Paz Castro (Universitat de València)