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    3rd COMETA General Meeting

    → Europe/Stockholm
    KVA

    KVA

    Lilla Frescativägen 4A, 11418 Stockholm
    Arnaud Ferrari (Uppsala University (SE)), Barry Dillon (Ulster University), Claudius Krause (MBI Vienna (ÖAW)), Eleni Vryonidou (University of Cyprus (CY)), Flavia de Almeida Dias (Nikhef National institute for subatomic physics (NL)), Francesco Armando Di Bello (Universita & INFN Pisa (IT)), Ilaria Brivio (University & INFN Bologna), Kadri Ozdemir (Izmir Bakircay University (TR)), Karlis Dreimanis (Riga Technical University (LV)), Karolos Potamianos (University of Warwick (GB)), Matteo Presilla (KIT - Karlsruhe Institute of Technology (DE)), Pietro Govoni (Universita & INFN, Milano-Bicocca (IT)), Rene Poncelet (IFJ PAN Krakow), Richard Ruiz (Institute of Nuclear Physics (IFJ) PAN), Valentina Cairo (CERN)
    Description

    The third COMETA General Meeting took place in Stockholm (Sweden) on June 1-3, 2026. It was hosted by the Royal Academy of Sciences (KVA).

    COMETA (COmprehensive Multiboson Experiment-Theory Action) is a COST Action that is devoted to improving measurements of multi-boson production processes at the LHC, their theoretical predictions, and their interpretation.

    The network currently includes 350+ researchers from over 44 countries within and outside Europe. It brings together theorists, experimentalists and machine learning experts, with the goal of creating a tightly interconnected community that can boost the development of innovative approaches to multi-boson measurements. The network also aims at creating an inclusive and informal environment, where young scientists and researchers based in underfunded European countries can gain international visibility.

    COMETA promotes a broad scientific program including:

    • BSM/EFT interpretation of multiboson measurements
    • precise SM predictions and event generation (MC+PS) for multiboson production processes
    • development of theory and tools to measure signals with polarised W and Z bosons
    • development of advanced Machine Learning tools in collaboration with professional ML practitioners
    • combined analyses of multiboson processes (H, HH, VV, VVV, VBS, etc) within the experimental collaborations

     

    For more information or to join the network, see: 
    - www.cost.eu/actions/CA22130/  
    - https://cometa.docs.cern.ch/

    Previous General Meetings: 

     

    Group picture:

     

    Short URL for the event: https://indico.cern.ch/e/cometa-gm3

     

     

    Participants
    65 View full list
    • Monday 1 June
      • 1
        Registration COMETA GM3
      • Working group 2
        Conveners: Barry Dillon (Ulster University), Dr Claudius Krause (MBI Vienna (ÖAW)), Francesco Armando Di Bello (Universita & INFN Pisa (IT))
      • 10:30
        Fika
      • Working group 3
        Conveners: Matteo Presilla (KIT - Karlsruhe Institute of Technology (DE)), Valentina Cairo (CERN)
      • 12:30
        Lunch
      • Working group 1
        Conveners: Eleni Vryonidou (University of Cyprus (CY)), Rene Poncelet (IFJ PAN Krakow)
      • 15:00
        Fika
      • Short talks
        • 11
          Electroweak PDFs at work

          At energies well above the electroweak scale, lepton collisions are dominated by collinear radiation of electroweak gauge bosons from the initial-state splittings. In this regime, VBF-like topologies become more important than s-channel annihilation processes. For future high-energy lepton colliders, such as a multi-TeV muon collider, Electroweak Parton Distribution Functions (EWPDFs) provide a convenient framework for describing these interactions, as they resum potentially large collinear logarithms and allow for a partonic interpretation of the hard process.

          In this contribution, we present the automated implementation of the EWPDF formalism in the Monte Carlo event generator Whizard. We demonstrate several applications of this framework to high-energy processes at future lepton colliders. Finally, we discuss whether the EWPDF approach can complement or partially replace standard fixed-order calculations, and to what extent it can improve the theoretical precision of future measurements.

          Speaker: Krzysztof Mekala
          EWPDFs_Mekala_COMETA.pdf
        • 12
          FMS on the lattice -- the structure of asymptotic states in weak physics (Part I)

          Gauge invariance requires physical states to be composite, even in the weak sector of the Standard Model (SM). The Fröhlich-Morchio-Strocchi (FMS) mechanism resolves this subtlety and predicts additional Higgs contributions in SM processes. In this talk, we give an introduction to the FMS mechanism, highlighting the consequences of a gauge-invariant approach to weak physics. After discussing our proxy theory using vectorial leptons on the lattice, we investigate the physical spectrum of the theory non-perturbatively and interpret our findings in the context of the FMS mechanism. Finally, we explore PDFs of the gauge-scalar subsystem, taking a closer look at the internal structure of the composite Higgs and W/Z bosons.

          Speaker: Georg Wieland (University of Graz)
          cometa26_wieland.pdf
        • 13
          FMS on the lattice -- the structure of asymptotic states in weak physics (Part II)

          While the complex structure of the spectrum of weak physics presented in part I of this talk calls for non-perturbative techniques, the FMS mechanism still offers an analytical approach: After fixing the gauge to produce a non-zero vacuum expectation value of a fundamental Higgs-field, we continue computing observables from gauge invariant operators with a regular perturbative approach yielding an augmented perturbation theory (APT). We will present results for spectral densities, cross sections, and PDFs from lattice field theory to corroborate the validity of APT.

          Speaker: Sofie Martins (University of Graz)
          cometa26_martins.pdf
        • 14
          Diboson production in the SMEFT at dimension-8

          We present a comprehensive analysis of dimension-8 and dimension-6 effects in fully leptonic WZ and WW production at the Large Hadron Collider (LHC) within the Standard Model (SM) Effective Field Theory (SMEFT). We focus on dimension-8 operators with maximal energy growth in the quark–(anti)quark-initiated production channel and assess their impact differentially through a variety of observables, including polarisation sensitive ones. Leveraging existing data from measurements at the LHC, we perform fits to quantify the sensitivity of current and future data to dimension-8 effects and evaluate their interplay with squared dimension-6 contributions. By marginalising over the dimension-8 operators we examine the robustness of a dimension-6 SMEFT analysis in diboson production. We find that dimension-8 effects become subdominant only for new-physics scales above 3 TeV.

          Speakers: Eleni Vryonidou (University of Cyprus (CY)), Hesham El Faham (The University of Manchester)
          vryonidouCOMETA.pdf
        • 15
          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)
          samuel_rosende_COMETA.pdf
        • 16
          Polarization Interference in Multiboson Production at the LHC

          LHC data and phenomenological estimates agree that polarization interference is inherently small for multiboson production at the LHC. In this talk, we show that this could be understood from kinematical arguments and angular momentum conservation, and is a non-trivial consequence of the (near) masslessness of initial- and final-state fermions coupling to intermediate, helicity-polarized weak bosons. We finish we a brief comment on minor adjustments to search strategies can lead to more robust/stable definitions of polarization across different classes of gauge fixing.

          Speaker: Richard Ruiz (Institute of Nuclear Physics (IFJ) PAN)
          rruiz_COMETA_PolInterference.pdf
        • 17
          Calibration of a Transformer-Based Quark/Gluon Tagger in ATLAS

          Distinguishing quark-initiated jets from gluon-initiated jets is a powerful handle for multiboson measurements at the LHC: in vector-boson scattering (VBS) and vector-boson fusion (VBF) topologies, quark/gluon tagging can enhance signal purity by identifying the characteristic quark-initiated forward jets and suppressing QCD-initiated backgrounds such as V+jets; additionally, the differing quark/gluon composition of the leading associated jet in gluon–gluon fusion (e.g. H+jet, predominantly gluon-initiated) versus electroweak processes (e.g. Z+jet, predominantly quark-initiated) offers a complementary discriminant for cross-section measurements and coupling extractions. This talk presents DeParT, a transformer-based quark/gluon tagger developed by ATLAS that exploits the full information from jet constituents reconstructed in both the tracker and calorimeter systems, operating across an extended kinematic phase space with $p_{\mathrm{T}} > 20$ GeV and $|\eta| < 4.5$. The tagger calibration is performed using dijet events from the LHC Run 2 and Run 3 proton–proton collision data, deploying the jet topics method — a data-driven technique that reduces reliance on Monte Carlo modelling, yielding up to 20% smaller systematic uncertainties compared to traditional approaches in some kinematic regions. The resulting efficiency scale factors enable robust application of the tagger across the ATLAS physics programme, with particular relevance for precision multiboson measurements and searches for new physics in VBS/VBF final states.

          Speaker: Samuel Jankovych (Nikhef National institute for subatomic physics (NL))
          Jankovych_Stockholm2026.pdf
    • Tuesday 2 June
      • Working group 2
        Conveners: Barry Dillon (Ulster University), Dr Claudius Krause (MBI Vienna (ÖAW)), Francesco Armando Di Bello (Universita & INFN Pisa (IT))
        • 18
          Foundation models for HEP experiments
          Speaker: Lukas Alexander Heinrich (Technische Universitat Munchen (DE))
          FoundationModels_Cometa.pdf
        • 19
          Simulation based inference for LHC experiments
          Speaker: Jay Ajitbhai Sandesara (University of Wisconsin Madison (US))
          SBI_at_LHC_COMETA.pdf
        • 20
          Lorentz equivariant neural networks and applications
          Speaker: Luigi Favaro (Universite Catholique de Louvain (UCL) (BE))
          cometa_equivariance.pdf
      • 10:30
        Fika
      • Working group 3
        Conveners: Matteo Presilla (KIT - Karlsruhe Institute of Technology (DE)), Valentina Cairo (CERN)
        • 21
          Highlights of the HL-LHC projections from ATLAS and CMS for the European Strategy Update
          Speaker: Pamela Ferrari (Nikhef National institute for subatomic physics (NL))
          stockholm_COMETA.pdf
        • 22
          Global EFT fits from Higgs and Electroweak measurements at the future circular colliders
          Speaker: Jorge de Blas (Universidad de Granada (ES))
          Global_Fits_FCC_deBlas.pdf
        • 23
          Open Data in ACTS
          Speaker: Daniel Thomas Murnane (Niels Bohr Institute, University of Copenhagen)
          ColliderML.pdf
          ColliderML.pptx
      • 12:30
        Lunch
      • Working group 5
        Conveners: Flavia de Almeida Dias (Nikhef National institute for subatomic physics (NL)), Karlis Dreimanis (Riga Technical University (LV)), Richard Ruiz (Institute of Nuclear Physics (IFJ) PAN)
      • Short talks
        • 26
          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)
          Clara Hernandez - COMETA Meeting.pdf
        • 27
          Two loop running effects in the effective Higgs gluon coupling

          In this study, we build upon existing literature on two-loop renormalization group equations (RGEs) for the dimension-six Standard Model Effective Field Theory operator involving two gluons and two Higgs bosons. This operator can generate an effective tree-level coupling between gluons and a Higgs boson, hence affecting the Higgs boson production via gluon-gluon fusion. In particular, we consider the contributions that enter the RGEs proportionally to $g_s^2 Y_{t,b}^2$.

          We also study the phenomenological impact of including two-loop running effects in Higgs physics fits at the LHC. To better probe this effect, we perform two kinds of fit. Firstly, using a bottom-up approach, we perform fits in terms of the Wilson Coefficients of the included operators to understand how their bounds are modified when running effects are included. Secondly, we specify ultraviolet models involving pairs of vector-like quarks (VLQs) coupled to third-generation Standard Model quarks, and we perform Higgs physics fits in terms of VLQ couplings.

          Speaker: Barbara Anna Erdelyi (Università degli Studi di Padova and INFN Sezione di Padova)
          Erdelyi_BA.pdf
        • 28
          A global stance on the importance of the 2-loop RGE

          We perform the first-ever global analysis of the importance of the full 2-loop RGE in SMEFT. We integrate the full set of two-loop RGE equations numerically and feed the result into the SMEFiT framework. With this, we evaluate its impact on global SMEFT fits at HL-LHC and FCC-ee. Then, we also fit a large set of tree and one-loop matched models to analyze the two-loop RGE impact on the sensitivity to specific New Physics scenarios. Based on upcoming work.

          Speaker: Alejo Nahuel Rossia (University of Padua and INFN Sezione di Padova)
          Rossia_COMETA_GralMeeting26.pdf
        • 29
          Light Z′ signatures via multiboson processes at the LHC

          This talk explores a unique $pp \rightarrow \text{Higgs} \rightarrow Z'Z' \rightarrow 4\ell$ ($\ell = e, \mu$) signal at the Large Hadron Collider (LHC). Within this context, the `Higgs' denotes either the Standard Model (SM)-like state discovered in 2012 or a lighter scalar emerging from a theoretical framework that includes a spontaneously broken $U(1)'$ gauge symmetry alongside the SM. This extended symmetry introduces a very light $Z'$ boson featuring non-universal vector and axial couplings to fermions. Notably, this model provides a compelling explanation for the Atomki anomaly while remaining fully consistent with current electron and muon Anomalous Magnetic Moment (AMM) measurements and existing beam dump constraints. We demonstrate that the expected cross section for this process is substantial enough to yield significant experimental sensitivity during LHC Run 3.

          Speaker: Dr Yasar Hicyilmaz (University of Southampton)
          COMETA_talk_yasar.pdf
      • 15:20
        Fika
      • Short talks
        • 30
          Search for di-Higgs in 2b + 2\tau channel via C2HDM

          In this work we have shown the possibility to probe the Composite two Higgs doublet model (C2HDM) via di-Higgs searches in HL-LHC. The additional vector-like heavy top quarks and additional CP-even scalars can play a significant role through additional loop contributions in gg->hh Feynman diagrams, which can make it significantly different than SM-like scenarios. We have performed a detailed collider analysis via the 2b 2\tau final state by considering all SM backgrounds, where a significant number of events can be detected in HL-LHC, whereas we can reduce all the major SM backgrounds.

          Speaker: Atri Dey
          atri_dey_diHiggs.pdf
        • 31
          Z boson and Higgs Factory Implications of Two Higgs Doublets with First-Order Phase Transitions

          We investigate the potential of future electron-positron colliders, such as FCC-ee and CEPC, to probe 2-Higgs-doublet models (2HDMs) that facilitate a strong first-order electroweak phase transition (SFOEWPT), a necessary condition for electroweak baryogenesis. Focusing on a 2HDM in the CP-conserving limit, we identify parameter regions consistent with an SFOEWPT and evaluate their compatibility with projected precision electroweak and Higgs measurements, as well as searches for exotic Higgs bosons. We show that radiative corrections to $e^+e^-\to hZ$ production introduce deviations in the cross section that are resolvable with the anticipated sub-percent precision at lepton colliders even when experimental outcomes of the LHC and $Z$ pole measurements are in agreement with the SM. This underscores the opportunities of a precision lepton collider to explore BSM quantum corrections to the Higgs sector more broadly.

          Speaker: Stefano Di Noi (KIT (ITP))
          COMETA3_Stockholm_DiNoi.pdf
          COMETA3_Stockholm_DiNoi_Static.pdf
        • 32
          HL-LHC gluon-fusion signatures of CP violation in extended scalar sectors

          Many well-motivated scalar extensions of the Standard Model (SM) predict new, purely bosonic sources of CP violation (CPV). In previous work, we established that the correlated observation of carefully selected bosonic processes provides a simple yet powerful strategy to unambiguously reveal the presence of CP violation. Within the Complex Two-Higgs Doublet Model (C2HDM), combinations of vector-associated production, vector boson fusion, and gluon fusion were shown to furnish robust CPV signatures. Building on this foundation, the present study completes the proposed CPV search framework by incorporating the remaining class of purely gluon-fusion-induced signatures. We analyze gluon-fusion production of the SM-like Higgs boson and its additional exotic neutral counterparts, followed by decays into $VV$ and $VH_i$ final states. By systematically exploring these channels across the different Yukawa realizations of the C2HDM, we provide a comprehensive and structurally complete assessment of bosonic CPV probes relevant for the HL-LHC.

          Speaker: Álvaro Lozano Onrubia (IFT UAM-CSIC)
          Presentation_COMETA_Álvaro_Lozano_Onrubia.pdf
        • 33
          Asymmetric cascade decays with bottom quark signatures in the extended Higgs sector

          While the discovery of the Higgs boson completed the Standard Model (SM), several fundamental questions remain unresolved, including the hierarchy problem and the nature of dark matter. Many well-motivated extensions of the SM introduce additional scalar bosons through an extended Higgs sector, providing rich phenomenology accessible at the LHC.
          A powerful strategy to probe such models is the search for cascade decays of heavy scalar resonances to lighter resonances. In this talk, we present a search for an asymmetric cascade decay in which a heavy scalar boson, $X$, decays into a lighter scalar boson, $S$, and a SM-like Higgs boson, $H$, with both subsequently decaying to bottom-quark pairs ($X \rightarrow SH \rightarrow b\bar{b}b\bar{b}$).
          The analysis uses the Run 2 dataset collected by the ATLAS detector. The four-bottom-quark final state offers strong sensitivity thanks to the large $H \rightarrow b\bar{b}$ branching ratio and state-of-the-art jet reconstruction and flavour tagging techniques, including algorithms optimised for boosted topologies. These developments allow us to probe a wide mass range for both $X$ and $S$, significantly extending the experimental reach for new scalar states predicted by extended Higgs sector models.

          Speaker: Varsha Senthilkumar (Nikhef National institute for subatomic physics (NL))
          VS20260603_COMETA_XSH_searches-5.pdf
      • Working group reports
        Conveners: Ilaria Brivio (University & INFN Bologna), Karolos Potamianos (University of Warwick (GB))
        • 34
          Report on WG1 activities
          Speakers: Eleni Vryonidou (University of Cyprus (CY)), Rene Poncelet (IFJ PAN Krakow)
          WG1 Report GM3.pdf
        • 35
          Report on WG2 activities
          Speakers: Barry Dillon (Ulster University), Dr Claudius Krause (MBI Vienna (ÖAW)), Francesco Armando Di Bello (Universita & INFN Pisa (IT))
          2026CometaGM_WG2.pdf
        • 36
          Report on WG3 activities
          Speakers: Matteo Presilla (KIT - Karlsruhe Institute of Technology (DE)), Valentina Cairo (CERN)
          cometa_4rdGMmeeting_WG3summary.pdf
        • 37
          Report from Grant Awarding Committee
          Speaker: Kadri Ozdemir (Izmir Bakircay University (TR))
          3rd COMETA Meeting GAC Report.pdf
        • 38
          Discussion
      • 19:00
        Dinner
    • Wednesday 3 June
      • Short talks
        • 39
          Efficient modeling of Di-Higgs signals for experimental searches at the LHC

          Since the discovery of the Higgs boson in 2012, great efforts have been made to understand this most vital particle of the Standard Model of particle physics (SM). With many quantities of this new boson now measured, the trilinear Higgs self coupling λ and double Higgs boson production (HH) has become a focal point of the LHC physics community and a core part of the ongoing and upcoming physics programme. With recent progress in experimental sensitivity and data gathered in the LHC Runs 2 and 3, the sensitivity for SM HH production will be reached soon, likely before the end of the upcoming HL-LHC.
          While a potential SM discovery is on the horizon, studying HH production also allows it to cover a multitude of physics beyond the SM including both EFT and resonant production.
          For experimentalists scanning vast amounts of physics scenarios, presents a significant computational challenge as the production and processing of necessary simulation remains a bottle neck. Therefore, to scan these vast ranges of parameters and operators effectively, suitable tools are needed to study BSM HH in a comprehensive and reinterpretable manner while maintaining consistency in treating BSM effects between different searches.
          This talk will look at signal modeling tools used to overcome these challenges such as the binned analytical reweighing of ggHH events to scenarios in the HEFT and SMEFT space, the matrix method to obtain HH signal shapes via linear combination of suitable templates, and recent efforts to upgrade these tools.

          Speaker: Torben Lange (National Institute of Chemical Physics and Biophysics (EE))
          matrix.pdf
        • 40
          ATLAS HH>bbyy SMEFT and HEFT Run-2 + partial Run-3 results

          Based on https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PUBNOTES/ATL-PHYS-PUB-2025-034/: Interpretations of a search for Higgs boson pair production in the bbyy final state using the Standard Model Effective Field Theory (SMEFT) and Higgs Effective Field Theory (HEFT) frameworks are presented. The search uses 140 fb-1 and 168 fb-1 of pp collision data at centre-of-mass energy of 13 TeV and 13.6 TeV, respectively, collected by the ATLAS detector at the Large Hadron Collider. Modifications to the gluon-gluon fusion and vector-boson fusion production cross sections induced by dimension-6 SMEFT operators and HEFT operators are considered. Modifications to the Higgs boson decay branching fractions due to EFT operators are also included. One-dimensional constraints at the 95% confidence level are derived for individual SMEFT operators using the linear and linear-plus-quadratic parameterizations. In HEFT, one and two-dimensional constraints at the 95% confidence level are derived. HEFT constraints are additionally derived while profiling other Wilson coefficients to their best-fit values. All results are consistent with the Standard Model predictions and provide insights into the validity of the SMEFT expansion and correlations among HEFT operators

          Speaker: Oleksii Kurdysh (Centre National de la Recherche Scientifique (FR))
          slide_55_cometa_jun26.pdf
        • 41
          Probing Dimension-8 Operators in Vector Boson Scattering with a Higgs (VBS VVh)

          The VBS VVh process has recently gained increasing attention, both theoretically and experimentally [1,2], as it provides a complementary probe to di-Higgs production with excellent sensitivity to the quartic gauge-Higgs coupling, VVHH, where V denotes either a W or Z boson.

          Published results so far model potential modifications to the quartic gauge-Higgs coupling within the κ-framework. In this study, we go beyond the κ-framework and explore the sensitivity of VBS VVh to beyond-the-Standard-Model effects using the dimension-8 Standard Model Effective Field Theory (SMEFT) framework [3].

          Dimension-8 operators have so far been studied primarily in VBS VV analyses, which probe quartic gauge couplings (VVVV). The same operators that affect quartic gauge couplings are also expected to impact the quartic gauge-Higgs coupling (VVHH). The unique sensitivity of VBS VVh therefore provides additional and complementary insights. In this talk, we will present our latest work at truth level and studying the sensitivity to those operator in a fiducial region compatible with the ATLAS detector to pave the way for future detector-level searches.

          [1] Henning et al. Higgs Couplings without the Higgs https://arxiv.org/pdf/1812.09299

          [2] The CMS collaboration. Search for associated production of a Higgs boson and of two vector bosons via vector boson scattering. https://cms-results.web.cern.ch/cms-results/public-results/preliminary-results/HIG-24-003/index.html

          [3] G. Durieux et al. LHC EFT WG Note: Basis for Anomalous Quartic Gauge Couplings https://arxiv.org/abs/2411.02483

          Speaker: Alexandro Martone (L2I Toulouse, CNRS/IN2P3, Université de Toulouse)
          AMartone_VVh_EFT_Cometa.pdf
        • 42
          Precise Predictions for Double Higgs Production Associated with a Vector Boson in Effective Field Theory

          This work presents a next-to-next-to-leading order (NNLO) QCD study of Higgs pair production in association with a vector boson, an important channel for probing Higgs boson couplings and beyond the Standard Model (BSM) physics. We obtain and compare predictions within two EFT frameworks - Standard Model Effective Field Theory (SMEFT) and Higgs Effective Field Theory (HEFT) - assessing the process’s sensitivity to BSM effects. Our analysis quantifies how such effects could manifest in LHC measurements, providing essential input for experimental searches and precision tests of the Standard Model.

          Speaker: Michal Jakub Ryczkowski (Università di Padova and INFN, Sezione di Padova)
          Ryczkowski_GM_COMETA_2026.pdf
        • 43
          Matching HEFT and SMEFT in double and triple Higgs production from VBF

          We focus on the bosonic sector of these two EFTs and do on-shell matching between HEFT and SMEFT by identifying their amplitudes for multiple Higgs production from VBF. By solving this matching, we extract a set of relations among their respective effective coefficients. In particular, we consider dim6 SMEFT operators and the dim8 SMEFT operators with 4-derivatives. In the HEFT, we consider effective operators up to chiral dimension 4. The solutions found allow to translate the constraints already known for the SMEFT to the HEFT coefficients.

          Speaker: Jose Daniel Domenech Moya (IFT - UAM)
          HEFT-SMEFT-matching-Estocolmo.pdf
        • 44
          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
          COMETA_GM3_Schmid.pdf
        • 45
          Global Fits at Future Colliders with the SMEFiT Framework

          We present projections for the New Physics reach of future high-energy colliders in the SMEFiT framework. Our analysis focuses on near-term electron–positron colliders (FCC-ee, LEP3, LCF), complemented in some cases by projections for the FCC-hh, LHeC, and MuCol. We include a wide range of processes, including Z-pole EWPOs, fermion-pair, Higgs, di-Higgs, diboson and top-quark pair production, as well as optimal observables for both $W^+W^-$ and $t\bar{t}$, while accounting for RGE evolution throughout. We quantify first their impact at the level of the global SMEFT parameter space, followed by several UV benchmark scenarios such as composite Higgs models, Two-Higgs-Doublet models and single particle extensions via UV matching.

          Speaker: Jaco ter Hoeve (The University of Edinburgh)
          COMETA-GM3-JtH.pdf
      • 10:30
        Fika
      • Working group 1
        Conveners: Eleni Vryonidou (University of Cyprus (CY)), Rene Poncelet (IFJ PAN Krakow)
        • 46
          ALPS+Multiboson
          Speaker: Maria Ubiali (University of Cambridge (GB))
          Ubiali_Cometa.pdf
        • 47
          Predictions for quantum observables
          Speaker: Morgan Del Gratta
          delgratta_cometa3.pdf
        • 48
          Precision for WBF Higgs production
          Speaker: Ivan Novikov
          slides.pdf
      • 12:30
        Lunch