Contact
Name
Sébastien Wertz

Position
Postdoc

Email
sebastien.wertz@cern.ch

Address
Centre for Cosmology, Particle Physics and Phenomenology - CP3
Université catholique de Louvain
2, Chemin du Cyclotron - Box L7.01.05
B-1348 Louvain-la-Neuve
Belgium

Phone
+32 10 473347
Projects
Research directions:
Phenomenology of elementary particles
Data analysis in HEP experiments
Detector commissioning, operation and data processing
Research and development of new detectors

Experiments and collaborations:
CMS

Active projects
a C++ software package to compute Matrix Element weights: MoMEMta
Florian Bury, Jérôme de Favereau, Christophe Delaere, Pavel Demin, Vincent Lemaitre, Sébastien Wertz

MoMEMta is a C++ software package to compute Matrix Element weights. Designed in a modular way, it covers the needs of experimental analysis workflows at the LHC. MoMEMta provides working examples for the most common final states (Formula: 0, WW, ...). If you are an expert user, be prepared to feel the freedom of configuring your MEM computation at all levels.
MoMEMta is based on:

- C++, ROOT, Lua scripting language
- Cuba (Monte-Carlo integration library)
- External PDFs (LHAPDF by default)
- External Matrix Elements (currently provided by our MadGraph C++ exporter plugin)
Search for Higgs boson(s) in CMS at the LHC in the llbb topology
Agni Bethani, Florian Bury, Jérôme de Favereau, Christophe Delaere, Khawla Jaffel, Vincent Lemaitre, Sébastien Wertz

Search for Higgs boson(s) within the Standard Model and beyond and also withing a minimal extension of the scalar sector (2HDM).

The final state under study is a Z decaying into a lepton pair associated with two b-jets. This topology is sensitive to a light SM Higgs via the associate ZH production, as well as a middle mass range SM Higgs boson via the inclusive Higgs production followed by its decay into ZZ with one Z decaying into a lepton pair and the other into bbar.

It is also very sensitive to the production of a non standard heavy Higgs boson decaying into Z plus A (pseudo scalar Higgs boson).

Similar selection (but outside of the Z window) is also sensitive to H->aa->llbb, with "a" a generic light scalar.

External collaborators: CMS collaboration.
Search for non-resonant new physics in ttbar production
Vincent Lemaitre, Sébastien Wertz

The lack of observed resonances produced at the LHC motivates finding new ways of searching for BSM phenomena. This project aims at discovering possible non-resonant New Physics affecting the production of Top quark pairs, by means of a dedicated analysis of data recorded by the CMS experiment. The New Physics effects are modeled using an effective field theory (EFT), whose parameters are to be measured or constrained in a global fit.

The analysis is conducted in close collaboration with phenomenologists to ensure the approach is theoretically sound and future-proof.
Search for nonresonant Higgs boson pair production in the llbb+MET final state
Agni Bethani, Florian Bury, Christophe Delaere, Martin Delcourt, Vincent Lemaitre, Fabio Maltoni, Sébastien Wertz

The discovery of a Higgs boson (H) by the ATLAS and CMS experiments fixes the value of the self-coupling λ in the scalar potential whose form is determined by the symmetries of the Standard Model and the requirement of renormalisability. Higgs boson pair production is sensitive to the self-coupling and will play a major role in investigating the scalar potential structure.

This project consists in a search for nonresonant Higgs boson pair production via gluon fusion in the final state with two leptons, two b jets and missing transvere energy – gg → H(bb) H(WW) asking for the leptonic decay of the W's. The analysis is conducted in close collaboration with phenomenologists to ensure the approach is theoretically sound and future-proof.
Search for resonant Higgs pair production in the llbb+MET final state
Agni Bethani, Florian Bury, Christophe Delaere, Martin Delcourt, Vincent Lemaitre, Sébastien Wertz

The recent discovery of a scalar boson compatible with the Standard Model (SM) Higgs boson opened new windows to look for physics beyond the SM (BSM). An example of newly accessible phenomenology is the production of resonances decaying into two SM Higgs bosons (h) predicted by several theory families such as additional Higgs singlet/doublet or warped extra dimension.

This project consists in a search for spin-0 or spin-2 resonances produced via gluon fusion in the final state with two leptons, two b-jets and missing transverse energy – gg → X → h(bb) h(WW) asking for the leptonic decay of the W's. In particular, we are probing a mass range between 260 GeV and 900 GeV.
Study and optimization of b-tagging performances in CMS
Agni Bethani, Christophe Delaere, Khawla Jaffel, Sébastien Wertz

We are involved in the activities of the btag POG (performance object group) of CMS, in release and data validation and purity measurement. We are also interested in btagging in special cases like for colinear b-jets. Furthermore, we are involved in the re-optimization and improvement of the Combined Secondary Vertex (CSV) tagger for the 2012 analyses.

External collaborators: Strasbourg CMS group, CMS collaboration.
The CMS silicon strip tracker upgrade
Florian Bury, Eduardo Cortina Gil, Jérôme de Favereau, Christophe Delaere, Martin Delcourt, Pavel Demin, Suat Donertas, Khawla Jaffel, Vincent Lemaitre, Maksym Teklishyn, Sébastien Wertz

Development of the "phase II" upgrade for the CMS silicon strip stracker.

More precisely, we are involved in the development of the uTCA-based DAQ system and in the test/validation of the first prototype modules. We take active part to the various test-beam campaigns (CERN, DESY, ...)

This activity will potentially make use of the cyclotron of UCL, the probe stations and the SYCOC setup (SYstem de mesure de COllection de Charge) to test the response to laser light, radioactive sources and beams.

The final goal is to take a leading role in the construction of part of the CMS Phase-II tracker.

External collaborators: CRC and CMS collaboration.

Non-active projects
Publications in CP3
All my publications on Inspire

Number of publications as CP3 member: 9 Download BibTeX

Last 5 publications

2020

CP3-20-33: Test beam demonstration of silicon microstrip modules with transverse momentum discrimination for the future CMS tracking detector
CMS Tracker Collaboration

[Journal] [Full text]
Published in: JINST 13 (2018) 03, P03003, Report number: FERMILAB-PUB-18-385-CMS, CERN-CMS-NOTE-2017-010

O. Bondu5, S. Brochet5, A. Caudron5, S. De Visscher5, B. Francois5, A. Jafari5, J. Cabrera Jamoulle5, M. Komm5, G. Krintiras5, A. Magitteri5, A. Mertens5, D. Michotte5, M. Musich5,, L. Quertenmont5, M. Vidal Marono5,
Refereed paper. July 2.
CP3-20-07: Report from Working Group 2 : Higgs Physics at the HL-LHC and HE-LHC
Cepeda, M. and others

[Abstract] [PDF] [Journal]
Public experimental note. January 26.

2019

CP3-19-29: Search for 2HDM neutral Higgs bosons through the H → ZA → llbb process
Alessia Saggio, Olivier Bondu, Miguel Vidal Marono, Christophe Delaere, Pieter David, Sebastien Wertz

[Full text]
Private experimental note. May 29.
CP3-19-28: Search for 2HDM neutral Higgs bosons through the H→ZA→ℓ+ℓ−bb process in proton-proton collisions at sqrt(s)=13 TeV
CMS collaboration

[Full text 1] [Full text 2]
Public experimental note. May 29.

2018

CP3-18-30: MoMEMta, a modular toolkit for the Matrix Element Method at the LHC
Brochet, Sébastien and Delaere, Christophe and François, Brieuc and Lemaître, Vincent and Mertens, Alexandre and Saggio, Alessia and Vidal Marono, Miguel and Wertz, Sébastien

[Abstract] [PDF] [Journal] [Dial]
Published in EPJ.C
Refereed paper. May 23.

More publications