1st COMETA General Meeting

28 Feb 2024, 09:30 → 1 Mar 2024, 16:30 Europe/Istanbul

Education Hall (İzmir, Türkiye)

Alessandra Cappati (Centre National de la Recherche Scientifique (FR)), Arnaud Ferrari (Uppsala University (SE)), Aysel Kayis Topaksu (Cukurova University (TR)), Claudius Krause (HEPHY Vienna (ÖAW)), Flavia De Almeida Dias (Nikhef National institute for subatomic physics (NL)), Giovanni Pelliccioli (Max-Planck-Institut für Physik), 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)), Ramona Groeber (Università di Padova and INFN, Sezione di Padova), Riccardo Finotello (CEA Paris-Saclay), Richard Ruiz (Fermi National Accelerator Lab. (US)), Valentina Cairo (CERN)

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

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.
It 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 very 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...) within the experimental collaborations

and much more. The network currently includes 150+ researchers distributed over 28 Countries within and outside Europe.

Sign up and more info at: www.cost.eu/actions/CA22130/   foswiki.web.cern.ch/COMETA/

Confirmed speakers: Christopher Schwan, René Poncelet, Luca Cadamuro, Marco Letizia, Jaco ter Hoeve, Peter Bokan, Toni Sculac, Alessandro Nada, Marco Vitti, Robert Schoefbeck, Alexandre Salas-Bernardez, Nurfikri Norjoharuddeen, Nicole Hartman, Alejo Rossia, Nathan Huetsch, Francisco Arco.

 

Honour Comittee:

Prof. Mustafa Berktaş (Rector)

Prof. Abdülkadir Hızıroğlu (Vice Rector)

Prof. Alparslan Kadir Devrim (Vice Rector)

 

Please note: photographs and video recordings will be taken by members of the local organising team and the COMETA outreach team. If you do not feel comfortable with this, please contact the organisers via email before the day of the event.

              

 

 

 

 

 

 

 

Wednesday, 28 February

Welcome: Prof. Mustafa Berktaş (Rector of the Bakırçay University)

WG 1,2,3 Presentations: WG1

Convener: Ilaria Brivio (University & INFN Bologna)

1 Precise SMEFT predictions

Speaker: Alejo Nahuel Rossia (University of Manchester)

Rossia_COMETA_Feb24.pdf

Rossia_COMETA_Feb24.pptx

2 HEFT and multi-Higgs predictions

Speaker: Mr Alexandre Salas-Bernárdez (Universidad Complutense de Madrid)

AlexandreSalasBernardez_Izmir.pdf

3 Precise polarisation predictions

Speaker: Rene Poncelet (IFJ PAN Krakow)

2024.02.28-Izmir-COMETA-1st-General-Meeting-poncelet.pdf

11:30 Coffee Break

WG 1,2,3 Presentations: WG2

Convener: Dr Claudius Krause (HEPHY Vienna (ÖAW))

4 Taggers for boosted HH searches within the ATLAS experiment

Speaker: Luca Cadamuro (IJCLab - CNRS/IN2P3 - Université Paris-Saclay (FR))

HH_boosted_taggers_COMETA_28Feb2024.pdf

5 Machine Learning for EFT interpretation

Speaker: Robert Schoefbeck (Austrian Academy of Sciences (AT))

24-02-29 Cometa general.pdf

24-02-29 Cometa general.pptx

6 Kernel methods for new physics searches

Speaker: Dr Marco Letizia

Cometa_Izmir2024_MarcoLetizia.pdf

13:30 Lunch

WG 1,2,3 Presentations: WG3

Convener: Matteo Presilla (KIT - Karlsruhe Institute of Technology (DE))

7 State-of-the-art of polarization measurements in multi-boson physics in ATLAS and CMS [20+10]

Speaker: Joany Manjarres (Laboratoire des 2 Infinis - Toulouse, CNRS / Univ. Paul Sabatier (FR))

20240228_COMETA2024_Polarization.pdf

8 Jet substructure measurements in multiboson processes with emphasis on VBS/VBF channels in ATLAS and CMS [20+10]

Speaker: Nurfikri Norjoharuddeen (Helsinki Institute of Physics (FI))

240228_COMETA_GM1_Nurfikri.pdf

9 State of the art of searches for Higgs exotic decays in ATLAS and CMS [20+10]

Speaker: Toni Sculac (University of Split Faculty of Science (HR))

COMETA_GM1_ExoticHiggs_Sculac.pdf

16:30 Coffee Break

WG5 Activities: WG5 Presentations

Convener: Karlis Dreimanis (Riga Technical University (LV))

10 WG5 Introduction and Updates

Speaker: Flavia De Almeida Dias (Nikhef National institute for subatomic physics (NL))

28Feb2024_WG5_COMETA.pdf

11 Brainstorming on WG5 activities

Outreach Event

20240228_COMETA-1.pdf

Thursday, 29 February

WG 1,2,3 Presentations: WG3

Convener: Pietro Govoni (Universita & INFN, Milano-Bicocca (IT))

12 State-of-the-art of HH and multi-Higgs searches in ATLAS and CMS [20+10]

Speaker: Petar Bokan (CERN)

20240229_COMETA2024_HH_PetarBokan.pdf

13 State of the art of VHH/VVH searches in ATLAS and CMS [20+10]

Speaker: Matteo Presilla (KIT - Karlsruhe Institute of Technology (DE))

VVH-VHH_Feb2024_Matteo.pdf

14 Flavour tagging performance in ATLAS and CMS with emphasis on HH and MultiHiggs searches [20+10]

Speaker: Nicole Michelle Hartman (TUM (DE))

Hartman-COMETA-FTAG-HH-builds.pdf

11:30 Coffee Break

WG 1,2,3 Presentations: WG1

Convener: Rene Poncelet (IFJ PAN Krakow)

15 Precision physics in hh, Zh, and ZZ production

Speaker: Marco Vitti

COMETA_Izmir_Vitti.pdf

16 Precise VBS predictions

Speaker: Mr Christopher Schwan (Universität Würzburg)

talk-schwan.pdf

17 BSM physics in multi-boson production

Speaker: Francisco Arco (UAM - IFT)

Arco-COMETA.pdf

13:30 Lunch

WG 1,2,3 Presentations: WG2

Convener: Dr Marco Letizia

18 Precision machine learning approaches

Speaker: Nathan Huetsch (Heidelberg University, ITP Heidelberg)

Izmir2024_MEM.pdf

19 Machine Learning based multivariate observables for global SMEFT fits

Speaker: Jaco ter Hoeve (Nikhef and VU Amsterdam)

COMETA_terHoeve.pdf

20 Normalizing flows for lattice field theory

Speaker: Alessandro Nada (Università di Torino)

nada_cometa_meeting.pdf

16:30 Coffee Break

Dissemination: Discussion of Communication and Dissemination Plan

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)

rruiz_COMETA_Izmir_SciComm.pdf

Short Talks Session

Conveners: Richard Ruiz (Fermi National Accelerator Lab. (US)), Richard Ruiz (Institute of Nuclear Physics (IFJ) PAN)

21 NLO EW corrections to polarised W+ W− production and decay at the LHC

With the help of the pole approximation, observables with polarised intermediate resonances can be calculated. Gauge-boson-pair production represents a particularly interesting class of processes to study polarisation. So far the computation of the NLO EW corrections was only possible for uncharged polarised resonances, since processes with charged resonances have additional infrared divergences from soft photon emission of the resonant propagators. In our calculation we canceled these infrared singularities with additional local counterterms.
This was used to compute the NLO EW corrections to polarised W+W- pair production in the double-pole approximation. On my poster I will present details of our calculation. It will be shown how the polarisation of the W bosons affects the shape of the differential distributions.

Speaker: Christoph Haitz

Präsentation_Cometa.pdf

22 Polarised cross sections for vector boson production with SHERPA

Measurements of vector boson (VB) polarisation in VB production processes offer a powerful probe of the electroweak symmetry breaking mechanism, scrutinising the Standard Model and new physics scenarios alike. Since massive VBs can only be observed as intermediate particles, polarised cross section templates from simulation are necessary to extract their polarisation from measurable unpolarised distributions. In this work we present an extension of the SHERPA Monte-Carlo event generator, allowing the simulation of polarised cross sections for VB production processes. Based on the narrow-width approximation, polarised cross sections of all possible polarisation combinations including the interference between different intermediate polarisation states for an arbitrary number of intermediate VBs can be simulated in a single simulation run. Besides polarised cross sections at fixed LO and LO+PS accuracy as well as in multi-jet merged calculations, we also present parton-shower-matched polarised cross sections with approximate NLO QCD corrections in the VB production processes.

Speaker: Diana Mareen Hoppe (Technische Universitaet Dresden (DE))

Polarized_XS_for_VB_production_Sherpa_MareenHoppe.pdf

23 Triboson production in the SMEFT

The processes of triboson production in high-energy proton–proton collisions provide a unique mean to probe the quartic interactions between EW gauge bosons and to perform indirect searches for physics beyond the Standard Model. Despite their small cross-sections, the production of 𝑉𝛾𝛾, 𝑉𝑉𝛾, 𝑉𝑉𝑉 (𝑉 = 𝑊 or 𝑍) at centre-of-mass energy of 13 TeV at the LHC has recently been observed by the ATLAS and CMS experiments. In this talk we present a SMEFT analysis based on total rates and differential distributions of triboson processes and show that NLO QCD corrections have striking effects on the sensitivity to dimension-6 operators. We finally present constraints on SMEFT operators from a global EW fit including electroweak precision observables (EWPOs), diboson (LEP & LHC) and triboson processes focussing on the impact of triboson measurements.

Speaker: Eugenia Celada

COMETA_Celada.pdf

24 A parton-level study on dimension-6 EFT operators in electroweak boson scattering processes at the LHC

A sensitivity study to new physics parametrized in the context of dimension-6 CP-even operators of the Standard Model Effective Field Theory (SMEFT) is obtained by combining several analyses performed at the parton-level. These include the production of opposite charged W bosos (W±W∓) and various flavours of VBS signatures (W±W±,W±W∓, ZZ, WZ) in leptonic or semi-leptonic final states. The effect of SMEFT operators in altering the SM predictions for VBS processes is included in both resonant and non-resonant diagrams O($\alpha_{EW}^6$), as well as in the corresponding QCD-induced backgrounds O($\alpha_{EW}^4 \alpha _{S}^2$).
An expected 95% CL confidence interval on the corresponding Wilson coefficient is then obtained by fitting an Asimov dataset generated under the SM hypothesis. Finally, the relative importance of each analysis is investigated by performing a simultaneous fit across all channels.
Based on A sensitivity study of VBS and diboson WW to dimension-6 EFT operators at the LHC.

Speaker: Giorgio Pizzati (Universita & INFN, Milano-Bicocca (IT))

pizzati_cometa.pdf

25 CMS Vector Boson Scattering SM combination and EFT at dimension-6 in the l\nu qq decay channel

Effective Field Theory (EFT) interpretations of the LHC data are gaining popularity as they allow to decouple analyses from a specific UV-complete model. All the leading dimension-six terms can be constrained only by combining inputs from Top, Higgs, EW and QCD physics. While typically Vector Boson Scattering (VBS) measurements are interpreted in terms of subleading dimension-eight EFT operators, they can provide useful orthogonal constraints in a global view. This work explores the sensitivity of the semileptonic VBS WV→lνqq to constrain eight dimension-six Wilson coefficients using 138/fb of data collected by CMS during Run-II. In view of a global EFT interpretation of VBS measurements, the simplest SM VBS combination will be presented using six public results from CMS using the Run-II dataset. The combination aims at measuring six purely EW production cross sections for W and Z boson pairs.

Speaker: Mr Giacomo Boldrini (Universita & INFN, Milano-Bicocca (IT))

Boldrini_COMETA_Izmir_299224.pdf

26 Quantum Collider probes of the fermionic Higgs Portal

Solutions to the dark matter puzzle and the hierarchy problem can include a BSM fermion $\psi$ that is a SM singlet and couples to the visible sector via a Higgs portal interaction: $\mathcal{L}_{H \psi} = c_{\psi}/f \ |H|^2 \bar{\psi} \psi$. Despite its potential of solving these tensions with the SM being well-established, the study of $\mathcal{L}_{H \psi}$ at hadron colliders remains challenging as the Higgs boson is the only portal between the $\psi$-particles and the SM sector. We study the interaction $\mathcal{L}_{H \psi}$ with several off-shell Higgs probes, namely the contribution of $\psi$ to the Higgs self-energy in $pp \rightarrow ZZ \rightarrow 4 \ell$ production, Di-Higgs production, and the direct production of $\psi$-pairs in off-shell Higgs decays. Finally, we present the combination of these three analyses providing complementary results and give an outlook on the collider reach of HL-LHC and other beyond-LHC $pp$-colliders in constraining the $\mathcal{L}_{H \psi}$ interaction.

Speaker: Konstantin Schmid (University and INFN Padova)

COMETA_Izmir_Schmid.pdf

27 An Anomaly Detection strategy for new physics searches at the LHC

We introduce a strategy based on unsupervised learning to identify new physics contributions in Vector Boson Scattering events at the LHC.

New physics contributions are modeled within the Standard Model Effective Field Theory (SMEFT) framework. Our anomaly detection strategy relies on Variational AutoEncoders (VAEs), which operate a dimensionality reduction and then map the lower dimensional representation back to the input space. The model is trained on a SM process, thereby learning to accurately reproduce its features. However, notable deviations in the output of the model are observed for instances generated through SMEFT. The reconstruction loss can thus be used to identify an anomaly-enriched region. As the model is solely trained on known physics, the strategy is independent of the specific nature of the chosen new physics process.

We demonstrate this strategy using parton-level generations of same-sign WW scattering events at the LHC, assuming an integrated luminosity of 350/fb.

Speaker: Giulia Lavizzari (Università degli Studi e INFN Milano (IT))

VAEs_dim6EFT_lavizzari.pdf

Meeting Dinner

Friday, 1 March

WG Summaries

Convener: Arnaud Ferrari (Uppsala University (SE))

28 Report on WG1 Activities

Speaker: Giovanni Pelliccioli (Max-Planck-Institut für Physik)

WG1 summary Izmir-1.pdf

29 Report on WG2 Activities

Speaker: Dr Claudius Krause (HEPHY Vienna (ÖAW))

COMETA.WG2.C.Krause.pdf

30 Report on WG3 Activities

Speaker: Matteo Presilla (KIT - Karlsruhe Institute of Technology (DE))

cometa_gm_WG3summary.pdf

31 Report on WG5 Activities

Speaker: Karlis Dreimanis (Riga Technical University (LV))

20240301_COMETA.pdf

Panel Discussion: Combined experimental analyses

The panel sessions have the goal of stimulating cross-WG discussions and start defining possible concrete targets for the Action.
The three topics chosen will be further developed within three corresponding topical COMETA meetings:

Workshop on Polarizations: Toulouse, September 23 - 24 2024
Workshop on Combined experimental analyses [CMS only]: Milano, May 23 - 24
Workshop on Boosted hadronic bosons: Vienna, July 15 - 17

32 Panel session on Combined experimental analyses

Speaker: Pietro Govoni (Universita & INFN, Milano-Bicocca (IT))

12:05 Coffee Break

Panel Discussion: W and Z boson polarizations, Boosted hadronic bosons

The panel sessions have the goal of stimulating cross-WG discussions and start defining possible concrete targets for the Action.
The three topics chosen will be further developed within three corresponding topical COMETA meetings:

Workshop on Polarizations: Toulouse, September 23 - 24 2024
Workshop on Combined experimental analyses [CMS only]: Milano, May 23 - 24
Workshop on Boosted hadronic bosons: Vienna, July 15 - 17

33 Panel session on W and Z boson polarizations

Speaker: Frank Siegert (Technische Universitaet Dresden (DE))

Polarisation panel COMETA Izmir.pdf

34 Panel session on Boosted hadronic bosons

Speaker: Petar Bokan (CERN)