IRN Terascale @ Montpellier

24 nov. 2025, 11:30 → 26 nov. 2025, 17:00 Europe/Paris

Ana M. Teixeira (LPCA - Clermont), Cyril Hugonie (LUPM), Elsa Teixeira (LUPM Montpellier), Gilbert Moultaka (LUPM Montpellier, UMR5299-CNRS/UM), Jean-Loic Kneur (LCC Montpellier), Marie-Helene Genest (LPSC-Grenoble, CNRS/UGA (FR))

 

We are looking forward to welcoming you for the fall meeting of the IRN Terascale in Montpellier on 24-26 November 2025.

Abstract submission and registrations are open, until October 24th for the abstracts and November 12th for the registration.

For any questions regarding the corresponding session, please contact the group conveners:

Higgs and EW	Iro Koletsou, Louis D'Eramo, Christophe Ochando, Pietro Slavich
BSM	Eric Chabert, Björn Herrmann, Romain Madar, Margarete Mühlleitner
Dark Universe	Julien Masbou, Emmanuel Moulin, Andreas Goudelis
Methods and Tools	Anja Butter, Mark Goodsell, Sabine Kraml

More information at terascale.in2p3.fr

We acknowledge partial support from the Montpellier University MIPS department. 

lun. 24 novembre

11:30 → 14:00 Accueil

14:00 → 14:20 Introduction / welcome / Announcements

Intro IRN Montpellier.pdf

welcome-presentation.odp

14:20 → 15:45 Methods and Tools

14:20 From hadron structure to fundamental symmetry: bridging theory and experiment with the gradient flow

Orateur: Andrea Shindler

movie_t_flow.gif

shindler_flow.pdf

15:05 Data-driven analyses and model-independent fits for present b→sℓℓ results

Talk based on https://arxiv.org/abs/2508.09986

Orateur: Siavash NESHATPOUR

Siavash_Montpellier.pdf

15:25 Polarized-boson pairs at NLO in the SMEFT

Based on https://arxiv.org/abs/2507.21768

Orateur: Emanuele Re

2025_11_24_montpellier.pdf

15:45 → 16:15 Coffee / Tea

16:15 → 18:00 Methods and Tools

16:15 Deconstructing signals of new physics at colliders - a case study with Higgs pair production

Multiple observations of phenomena which cannot be explained in the Standard Model suggest that we need new physics beyond what we already know. The proliferation of theories in the last decades and the absence of direct observation of new phenomena at the LHC suggests to develop analysis strategies as model-independent as possible, yet suitable to be applied in experimental searches at current or next-generation colliders. One of the critical points in performing this kind of phenomenological analyses is that, very often, large parameter scans are necessary: intensive and often redundant MC simulations have to be performed to cover relevant regions of signal parameter space and achieve enough accuracy in the determination of signal features. On the other hand, disk space and computing time are often limited, and the environmental impact of performing such computations is seldom taken into consideration. There is a growing need to devise strategies to optimise data production and share resources in the HEP community, both theory and experiment. I will describe a framework which allows such approach, where simulated signal samples are deconstructed into complete sets of basic elements to be combined a posteriori to perform different analysis. The framework is modular, collaborative, flexible and resource-friendly. I will describe it through concrete examples for specific phenomenological analyses and indicate possible short- and long-term developments and applications.

Orateur: Luca Panizzi

HHdeconstruction.pdf

16:35 Six-Top Final States in the Top-Portal FPVDM: New Reinterpretation Opportunities

The Fermionic Portal Vector Dark Matter (FPVDM) framework generically predicts six-fermion final states arising from pair production of heavy vector-like fermions followed by dark-sector cascade decays. In the top-portal realisation (TPVDM), this structure leads to a distinctive and essentially background-free six-top final state, which persists across almost the entire parameter space compatible with gravitational-wave, relic-density, and direct-detection constraints.
I will present new reinterpretation results for this six-top signature using ATLAS and CMS Run-2 analyses targeting high jet multiplicities, multi-b final states, and top-rich topologies. A dedicated CLs-based combination of mutually orthogonal signal regions extends current limits by up to O(100 GeV) compared with any single analysis. First HL-LHC projections reach the 2.2-2.3 TeV mass range for the vector-like fermions.
The talk will focus on the six-top realisation of the top portal, while briefly outlining prospects for other FPVDM realisations that generate different six-fermion signatures. This identifies a concrete, underexplored opportunity for LHC reinterpretation.

Based on: https://arxiv.org/abs/2508.04912 , https://arxiv.org/abs/2204.03510 , https://arxiv.org/abs/2203.04681

Orateur: Alexander Belyaev

Belyaev-Terascale-Motpelier-2025-6tops.pdf

16:55 Scaling laws for amplitude surrogates

Fast and precise evaluations of scattering amplitudes even in the case of precision calcu-
lations is essential for event generation tools at the HL-LHC. We explore the scaling behav-
ior of the achievable precision of neural networks in this regression problem for multiple
architectures, including a Lorentz symmetry aware multilayer perceptron and the L-GATr
architecture. L-GATr is equivariant with respect to the Lorentz group by its internal em-
bedding living in the geometric algebra defined by the flat space-time metric. This study
addresses in particular the scaling behavior of uncertainty estimations using state of the
art methods.

Orateur: Joaquín Iturriza Ramirez (Lpnhe)

Scaling laws for amplitude surrogates.pdf

17:15 A Guided Tour of Quantum Computing and the French Quantum Landscape

Orateur: Mariane Mangin-Brinet (LPSC/CNRS)

QC_IRNTerascale_pdf.pdf

mar. 25 novembre

09:30 → 10:45 Higgs and Electroweak

09:30 Theoretical Inputs for Vector-Boson Scattering Measurements at the LHC

Vector-boson scattering (VBS) is a key process for probing the mechanism of electroweak symmetry breaking at the LHC. Precise measurements of VBS offer stringent tests of perturbative unitarity, enable the extraction of longitudinal gauge-boson polarisation components, and provide sensitivity to scenarios beyond the Standard Model. This presentation outlines the theoretical inputs required to fully exploit current and future VBS measurements. In particular, I will highlight the intricate interplay between theory and experiment in interpreting these measurements and maximizing their discovery potential.

Orateur: Mathieu Pellen (University of Freiburg)

PELLEN_IRN_Montpellier_2025.pdf

09:55 Measurements and interpretations of $W^{\pm}Z$ production cross-sections in $pp$ collisions at $\sqrt{s}$= 13 TeV with the ATLAS detector

The study of $W^{\pm}Z$ diboson production is of great interest as an essential test of the Standard Model (SM) and as an effective tool for searching for new physics effect. This talk will present the latest ATLAS measurements of the integrated and differential cross-sections of the process $pp \to W^{\pm}Z$ in the leptonic decay modes with electrons and muons at an energy in the center of mass of 13 TeV. The complete Run 2 data sample is used corresponding to 140 fb$^{-1}$. The results are compared with SM predictions from state-of-the-art event generators and from fixed-order calculations.
The measurements are interpreted in the context of an effective field theory considering both CP-conserving and CP-violating dimension-6 operators modifying the WZ production. Limits on CP-conserving Wilson coefficients are extracted using the transverse mass of the $W^{\pm}Z$ system. For CP-violating coefficients a machine learning approach is used to construct an observable with enhanced sensitivity to CP-violation effects.

Orateur: Léo Boudet

WZ_ATLAS_13TeV.pdf

10:20 Constraints on new physics using Higgs pT STXS measurements with H1jet and HiggsSignals

We present a phenomenological study on the constraints of new physics using Simplified Template Cross Section (STXS) measurements of the Higgs transverse momentum distribution with H1jet and HiggsSignals. H1jet is a fast code that computes the transverse momentum distribution of a colour-singlet, allowing for quick scans over the parameter space in various Beyond-the-Standard Model (BSM) scenarios. The predictions are provided through a novel interface to HiggsSignals in order to perform statistical tests against STXS measurements of Higgs boson signal rates from the LHC and projected rates for the HL-LHC. The BSM models considered includes generic top-partner models, composite Higgs models, the MSSM (using an interface with FeynHiggs), and the inclusion of dimension-8 Higgs operators.

Orateur: Alexander Lind (INFN Laboratori Nazionali di Frascati (LNF))

Lind_IRNTerascaleMontpellier.pdf

10:45 → 11:15 Coffee / Tea

11:15 → 12:30 Higgs and Electroweak

11:15 CP-sensitive Simplified Template Cross Sections for ttH

The structure of the Higgs boson remains one of its least precisely constrained properties. Possible $\mathcal{CP}$ violation in the Yukawa interaction between the Higgs boson and the top quark can be directly probed at the LHC through measurements of top-quark-associated Higgs production ($t\bar{t}H$). Current multivariate analysis strategies are typically optimized for specific signal models, which limits their reinterpretation and combination potential.

To address this, we propose a $\mathcal{CP}$-sensitive extension of the Simplified Template Cross Section (STXS) framework. Considering multiple Higgs decay channels, we perform a detailed comparison of $\mathcal{CP}$-sensitive observables and their combinations. The proposed extension augments the existing Higgs transverse momentum binning, $p_{\mathrm{T},H}$, with additional observables such as the pseudorapidity difference between the top quarks, $\Delta\eta_{t\bar{t}}$, or kinematic variables derived from the top-quark momenta, including $b_2$ and the Collins--Soper angle $|\cos\theta^{*}|$.

This approach achieves near-optimal sensitivity to the $\mathcal{CP}$ admixture in the top Yukawa coupling for an integrated luminosity of $300~\mathrm{fb}^{-1}$, and shows further improvement with a two-dimensional STXS extension at $3000~\mathrm{fb}^{-1}$. Work is ongoing to incorporate a dedicated top-quark definition within the STXS framework to enhance the robustness and interpretability of future measurements.

Orateur: Alberto Carnelli (LAPP (CNRS), CERN)

IRN_terascale_Montpellier_Carnelli.pdf

11:40 Triple Higgs production at the LHC and ATLAS results

Ten years after the discovery of the Higgs boson by the ATLAS and CMS experiments, the study of its properties remains one of the main targets of LHC physics.
Among these properties, the Higgs self-coupling parameters are of particular interest, as they are directly related to the shape of the Higgs potential: the SM Higgs Lagrangian contains two self-interaction terms corresponding to trilinear and quartic interactions.
While direct production of two Higgs bosons (HH) provides the most sensitive test of the Higgs trilinear self-coupling, in order to access the quartic Higgs self-coupling the investigation of Triple Higgs production (HHH) is necessary.
HHH production processes are extremely rare at the LHC (roughly 1000 times more than HH pair production) and constitute a very difficult experimental challenge.
In this presentation I propose to discuss the phenomenological framework which motivates the study of HHH production at the LHC as a probe of the Higgs potential parameters, as well as a window towards new physics, to discuss the ATLAS results in the search for HHH production in the 6 bottom-quark decay channel [1], and furthermore to highlight the projection of these results towards the HL-LHC phase [2].
While this process in the SM is still out of reach of the current experimental sensitivity, it represents a growing area of interest (with recent results from the CMS collaboration as well), which would benefit from further discussions among experimentalists and theorists.

[1] https://journals.aps.org/prd/abstract/10.1103/PhysRevD.111.032006
[2] https://cds.cern.ch/record/2924772

Orateur: Carlo Pandini (LPSC)

HHH_IRN_Terascale_Pandini_2025_11_25.pdf

12:05 $e^-e^+\rightarrow s \bar{s}$ at $\sqrt{s}=250$ GeV in future linear colliders [from BSM]

Future Higgs Factories will offer a clean environment to study $e^-e^+\rightarrow q \bar{q}$
processes ($q=d,u,s,c,b$) at various centre-of-mass energies, from the Z-pole up to the TeV scale. In this contribution, we focus on the case of $e^-e^+\rightarrow s \bar{s}$
at $\sqrt{s}=250$ GeV, using full simulation and reconstruction within the ILD detector concept to evaluate differential observables and their sensitivity to detector performance.

We explore event preselection strategies to suppress backgrounds (such as
$W^-W^+$, $ZZ$, and $ZH$), and explore different jet clustering algorithms and flavour tagging tools. Particle identification using dE/dx is crucial for identifying charged kaons, which plays a key role in both strange-jet tagging and the reconstruction of the jet charge. We study the performance of the standard ILD flavour tagging package, LCFIPlus, and investigate the impact of more recent developments based on Particle Transformer models. Finally, we discuss how these results can enhance the sensitivity to possible manifestations of physics beyond the Standard Model.

Orateur: Jesus Pedro MARQUEZ HERNANDEZ (IJCLAB (CNRS))

ssbar_TeraScale.pdf

12:30 → 14:15 Lunch

14:15 → 15:30 Beyond the Standard Model

14:15 Asymmetries in polarized cLFV $\tau$ and $\mu$ decays in the presence of heavy sterile fermions

In the context of Standard Model extensions via Majorana sterile fermions, the presence of additional CP violating phases (Dirac and Majorana) has been shown to be at source of important effects in charged lepton flavour violating (cLFV) transitions and decays.
Here we will consider further angular observables that can be studied for polarised $\tau$ and $\mu$ cLFV decays. These include, among others, parity asymmetries and time-reversal asymmetries for generic cLFV 3-body decays, $\ell_\alpha^+ \to \ell_\beta^+ \ell_\gamma^+ \ell_\delta^-$. We address relevant correlations between the different classes of observables, and show that one can have sizeable asymmetries, which can be used to further probe this interesting class of SM extensions.

Orateur: Adrian Darricau (LPCA)

Adrian Darricau Terascale Montpellier 2025.pdf

14:33 Quantum Sensing Signatures of Axion-Like Particles

Axion-like particles (ALPs) are compelling dark matter candidates, particularly in the "ultralight mass regime." In this talk, I will discuss the theoretical framework for ALP interactions with Standard Model fields, emphasising the renormalization group (RG) running and low-energy matching in quantum field theory. Many quantum sensor experiments are designed to probe very light ALPs, which are especially sensitive to these effects due to large decay constants, where running effects become significant. Furthermore, while linear axion interactions are dictated by their pseudoscalar nature, quadratic interactions resemble scalar interactions, leading to distinct experimental signatures. I will explore the discovery potential of various quantum technology-based experiments, including atomic clocks, interferometers, haloscopes, and fifth force searches.

Orateur: Sreemanti Chakraborti (IPPP Durham)

IRN_nov25sc.pdf

14:51 Probing Axion-Like Particles in Association with Top Quarks at Colliders

Axion-Like Particles (ALPs), arising from spontaneous global symmetry breaking in many Standard Model extensions, provide a compelling avenue for probing new physics. We study ALP production in association with top quarks through several channels at the LHC and future colliders. We focus in particular on light ALPs that escape detection and appear as missing transverse energy. Using full Run 2 data at 13 TeV, we analyze ttbar+ALP events in the semileptonic and dileptonic decay modes to set limits on ALP couplings to top quarks and gluons. We also investigate single top production with a W boson and an ALP, using spin correlation measurements to further constrain couplings to W bosons. Projections for the HL-LHC and FCC-hh show that ttbar+ALP channel offer excellent sensitivity to ALP–gluon and ALP–EW couplings. Our results include two-dimensional exclusion limits and comparisons with indirect bounds from B-meson decays and top (chromo)magnetic dipole moments.

Orateur: Mojtaba Mohammadi Najafabadi (CERN and IPM)

NajafabadTalkMontpellier-25-11-25.pdf

15:09 Light Scalars in Light of UV/IR Mixing

Light scalar fields are ubiquitous in theoretical (astro)particle physics and cosmology. From the perspective of effective field theories, these scalars encounter hierarchy problems unless their masses are protected by a symmetry. Non-standard UV completions involving non-localizable fields may introduce correlations between short and long distances, thereby generating a UV/IR mixing that could account for the existence of light scalars with little hierarchies. In this talk, I will present a concrete realization of this concept within the framework of self-completion by classicalization, a mechanism proposed fifteen years ago by Dvali et al.

Orateur: Dr Florian NORTIER (CNRS/IN2P3 - IP2I Lyon)

Slides Terascale Montpellier 2025.pdf

15:30 → 16:00 Coffee / Tea

16:00 → 17:15 Beyond the Standard Model

16:00 Infrared Phases of Chiral Gauge Theories

Gauge-fermion theories and their IR fate remain puzzling mysteries in QFT, even after decades of study. Beyond their theoretical interest, they could play a natural role in extensions of the SM, such as GUTs, dynamical symmetry breaking, and models of quark and lepton substructure. Yet our ignorance of these models severely hampers their potential application to realistic theories of nature. Therefore, it is of utmost importance to gain knowledge about their dynamics. By use of functional methods and the Effective Average Action we investigate for the first time from first principles the IR of a particular class of Chiral Gauge Theories [1,2]. Our results show a rich structure, from the existence of IR conformality to new patterns of Chiral Symmetry Breaking.

[1] Dynamical symmetry breaking in Georgi-Glashow chiral-gauge theories, Hao-Lin Li (Zhongshan U.), Álvaro Pastor-Gutiérrez (Wako, RIKEN and Leuven U.), Shahram Vatani (Louvain U., CP3), Ling-Xiao Xu (ICTP, Trieste) e-Print: 2507.21208 [hep-th]
[2] Dynamical symmetry breaking in Bars-Yankielowicz chiral-gauge theories, Hao-Lin Li (Zhongshan U.), Álvaro Pastor-Gutiérrez (Wako, RIKEN and Leuven U.), Shahram Vatani (Louvain U., CP3), Ling-Xiao Xu (ICTP, Trieste), in preparation

Orateur: Shahram Vatani (CP3 UCLouvain)

TeraSlideVatani.pdf

16:18 Renormalization of Asymptotic Grand Unified Theories

The idea of introducing extra spacetime dimensions has long been viewed as a promising way to extend the Standard Model, offering new tools to address some of its limitations. One interesting example is provided by asymptotic Grand Unified Theories (aGUTs), where the gauge couplings of the Standard Model forces do not unify at a single high-energy scale but instead evolve toward a common fixed point in the ultraviolet (UV) regime. Although higher-dimensional theories are found to be non renormalizable and usually considered as effective field theories, they can still be considered fundamental within the framework of asymptotic safety. In my work, I study five-dimensional gauge theories to explore the existence of such fixed points, which would ensure their consistency at very high energies. I also investigate the appearance of both bulk and localized divergences on the boundaries of the 5th dimension, in order to better understand how renormalization operates in these higher-dimensional settings.

Orateur: Wanda Isnard (IP2I Lyon)

IRN_Montpellier.pdf

16:36 Artificial Proto-Modelling for Dispersed Signals at the LHC

Despite the success of the Standard Model of particle physics, several evidence point towards the existence of physics beyond the Standard Model. However, no compelling signal of new physics has been observed so far, notwithstanding the slew of dedicated experimental searches. The absence of positive results and the stringent constraints reflect the need to shift from the usual top-bottom, theory-driven approach. The proto-model machine, initially published as a proof-of-concept, goes in that direction and proposes a more model-independent, data-driven approach aimed at highlighting dispersed beyond the Standard Model signals should they be hiding in LHC data. This presentation will introduce an improved version of this machine, with a more furnished database, a refined statistical treatment, and the possibility to probe off-shell regions of the parameter space. The current best fitting model, i.e. the one maximally violating the Standard Model while respecting LHC constraints, will also be discussed.

Orateur: Timothee Pascal

artificial_protoModelling_dispersed_LHC_signals.pdf

16:54 Triple Higgs production at proton proton colliders [from Higgs+EW]

In this talk, we will discuss the feasibility of measuring the Higgs self couplings through triple Higgs production at future proton–proton colliders. In particular, our study will focus on the 6 b final state.
Moreover, we will explore the possibility of detecting extra scalars at the LHC as a result of an enhanced triple Higgs production cross section, with a particular emphasis on the Two Real Singlet Model.

Orateur: Gilberto Tetlalmatzi-Xolocotzi

Montpellier.pdf

17:15 → 18:00 SMC meeting

20:00 → 23:30 Dîner

Brasserie du Théâtre

mer. 26 novembre

09:00 → 10:30 Dark Universe

09:00 XLZD Sensitivity to WIMPs via the Migdal Effect

This talk presents a projected sensitivity for the XLZD detector to Weakly Interacting Massive Particles (WIMPs) via the Migdal effect. For very light WIMPs, the nuclear recoils they induce are often below detection threshold, but the associated Migdal ionisations may still produce detectable signals. The study models the expected Migdal ionisation signal and background response under realistic detector assumptions, extending the reach of future xenon-based experiments toward lower WIMP masses.

Orateur: Lorenzo Principe (SUBATECH)

IRN Terascale 2025.pptx

09:30 The Hubble tension: A health check of cosmological models

Review talk on the Hubble tension

Orateur: Dr Elsa Teixeira (LUPM Montpellier)

IRN_Teixeira.pdf

10:00 No room for monopole dark matter

The magnetic monopole of a dark sector has been advocated as an appealing dark matter candidate. We recently revisited the computation of the monopole abundance, produced by a thermal phase transition in the minimal 't Hooft-Polyakov model. We explored the three regimes where the phase transition is second order, weakly first order, or supercooled, identifying the regions of parameter space where the monopole abundance can account for the observed dark matter density. However, the dark sector necessarily contains a stable electrically-charged particle, namely, a massive vector boson, with a calculable abundance. Under minimal assumptions, we show that the vector boson always dominates the dark matter density: dark monopoles cannot constitute a sizeable fraction of dark matter.

Orateur: Théodore Fischer (LUPM)

Theodore_Fischer.pdf

10:30 → 11:00 Coffee / Tea

11:00 → 12:00 Dark Universe

11:00 Freeze-in with low reheating temperature

The freeze-in mechanism is an alternative mechanism for dark matter production to standard thermal freeze-out. Freeze-in computations are typically performed assuming a very high initial ("reheating") temperature. However, this temperature is poorly constrained and can take relatively small values. I will discuss dark matter freeze-in in such a scenario and highlight how dark matter production is impacted compared with the "infinite" reheating temperature case.

Orateur: Thomas REGGIO (LPCA)

Terascale_MTP_Reggio_2025 .pdf

11:30 Ultra-Relativistic Freeze-Out During Reheating

Dark matter remains one of the major puzzles of both modern cosmology and particle physics. While the freeze-out mechanism is getting more and more constrained, motivating revisions during non-standard cosmologies such as reheating, the freeze-in mechanism is intrinsically difficult to probe, motivating people to invoke stronger couplings. In this talk, I will present an alternative through relativistic freeze-out during reheating. While usual relativistic freeze-out usually overproduces dark matter, I will present how entropy injection during reheating can properly dilute the dark matter abundance to match observations, thus opening a new window for dark matter production.

Orateur: Mathieu GROSS (IJCLab)

Ultra-relativistic freeze-out (UFO) during reheating terascale 2025.pdf

12:00 → 12:20 Famous last words and early-career scientist talk prize announcement