Christophe Delaere

Academic staff


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

+32 10 47 3207


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LPHYS1345 - Etat solide
Ce cours constitue une introduction à la physique de l'état solide. En ce sens, sont abordés les différentes propriétés thermiques et électriques du solide. On mettra l'accent sur l'application des notions de base aux semi-conducteurs (applications micro-électroniques et techniques de détection des particules chargées) et à la supraconductivité.

MAFY1181 - Actualité de la physique
Cette activité a pour but de motiver l'étudiant en lui donnant une image ouverte et attrayante de la physique et des mathématiques d'aujourd'hui. Elle l'aidera aussi à préciser son choix d'études au-delà de la première année.
Mon séminaire porte sur le démarrage du LHC et les principaux objectifs de l'expérience CMS, parmis lesquels la recherche du boson de Higgs.

LPHY2131 - Physique des particules élémentaires I
Pour 1/3 du cours : Rappel : Constantes fondamentales et unités Matière ordinaire et unifications (quark-lepton) Anti-matière et symétries discrètes (C,P,T) Matière extraordinaire et masses (matrices de mélange CKM et MNS) Pour 2/3 du cours : partie expérimentale On discute ici plus en détail les expériences présentées dans le cours PHY1331. Une revue des découvertes de ces particules + des expérience liées à la violation de CP

LPHY2135 - Computing et Méthodes numériques en physique des particules
Sélection en ligne d'événements (systèmes de déclanchement et sélection hardware et software) - Méthodes de reconstruction d'événements : Tracking, vertexing, clustering et identification de particules. Techniques de calibration et alignement. - Techniques d'analyse des données - Générateurs MonteCarlo d'interactions entre particules - Simulation de la propagation de particules dans la matière. Des travaux personnels, largement informatisés, ayant pour but la simulation d'une expérience en physique des particules intégreront les cours théoriques.
People responsibilities
Sandhya Jain (IISN - CMS phase 2) (member since December 2020)
Experimental high energy physicist working with the CMS experiment at the LHC. Currently involved in phase-2 outer tracker R & D activities and exploring physics possibilities with upgraded CMS detector at the HL-LHC. Profound background in physics analysis and in the CMS data analysis framework. Important responsible for performing SEU tests and analysis for the CMS outer tracker FE ASIC Concentrator Integrated Circuit (CIC) for Phase-II upgrades. Worked on key aspects within test beam activities for tracker as well as Endcap Calorimeter (HGCal) for Phase-II CMS detector. Performed system tests for High Granularity Calorimeter (HGCal).
Sébastien Wertz (IISN - IISN CMS-BSM) (member since September 2013)
Experimentalist with the CMS collaboration. Searches for non-resonant new physics in the llbb+MET topology (hh and ttbar processes). Also involved in the development of new tools easing the use of the Matrix Element Method.

PhD students
Suat Donertas (IISN) (member since October 2019)
Experimentalist, working on CMS Tracker Phase 2 Upgrade.
Khawla Jaffel (EOS) (member since December 2018)
** Search for heavy resonance decaying into H/A -> Z A/H -> ll bb ** I am a PhD student working on beyond the Standard Model (BSM) physics. Addressing the question of whether additional scalar resonance exists, searching for a signature consisting of two b-tagged jets and two opposite-charge, same flavour leptons originating from Z bosons in one of the simplest extensions of the Standard Model (SM), the Two Higgs Doublet Model (2HDM).

Former members
Research directions:
Data analysis in HEP, astroparticle and GW experiments
Detector commissioning, operation and data processing
Phenomenology of elementary particles
Research and development of new detectors

Experiments and collaborations:

Active projects
a C++ software package to compute Matrix Element weights: MoMEMta
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)
Advanced Multi-Variate Analysis for New Physics Searches at the LHC
Christophe Delaere, Andrea Giammanco, Vincent Lemaitre, Fabio Maltoni

With the 2012 discovery of the Higgs boson at the Large Hadron Collider, LHC, the Standard Model of particle physics has been completed, emerging as a most successful description of matter at the smallest distance scales. But as is always the case, the observation of this particle has also heralded the dawn of a new era in the field: particle physics is now turning to the mysteries posed by the presence of dark matter in the universe, as well as the very existence of the Higgs. The upcoming run of the LHC at 13 TeV will probe possible answers to both issues, providing detailed measurements of the properties of the Higgs and extending significantly the sensitivity to new phenomena.

Since the LHC is the only accelerator currently exploring the energy frontier, it is imperative that the analyses of the collected data use the most powerful possible techniques. In recent years several analyses have utilized multi-variate analysis techniques, obtaining higher sensitivity; yet there is ample room for further improvement. With our program we will import and specialize the most powerful advanced statistical learning techniques to data analyses at the LHC, with the objective of maximizing the chance of new physics discoveries.

We have been part of AMVA4NewPhysics, a network of European institutions whose goal is to foster the development and exploitation of Advanced Multi-Variate Analysis for New Physics searches. The network offered between 2015 and 2019 extensive training in both physics and advanced analysis techniques to graduate students, focusing on providing them with the know-how and the experience to boost their career prospects in and outside academia. The network develops ties with non-academic partners for the creation of interdisciplinary software tools, allowing a successful knowledge transfer in both directions. The network studies innovative techniques and identifies their suitability to problems encountered in searches for new physics at the LHC and detailed studies of the Higgs boson sector.

External collaborators: University of Oxford, INFN, University of Padova, Université Blaise Pascal, LIP, IASA, CERN, UCI, EPFL, B12 Consulting, SDG Consulting, Yandex, MathWorks.
CMS Tracker commissioning and performance assessment
Christophe Delaere

The CMS silicon strip tracker is the largest device of its type ever built. There are 24244 single-sided micro-strip sensors covering an active area of 198m2.
Physics performance of the detector are being constantly assessed and optimized as new data comes.
Members of UCL are playing a major role in the understanding of the silicon strip tracker and in the maintenance and development of the local reconstruction code.

External collaborators: CMS tracker collaboration.
Development of a framework for fast simulation of a generic collider experiment: Delphes
Jérôme de Favereau, Christophe Delaere, Pavel Demin, Andrea Giammanco, Vincent Lemaitre

Observability of new phenomenological models in High Energy experiments is delicate to evaluate, due to the complexity of the related detectors, DAQ chain and software. Delphes is a new framework for fast simulation of a general purpose experiment. The simulation includes a tracking system, a magnetic field, calorimetry and a muon system, and possible very forward detectors arranged along the beamline. The framework is interfaced to standard file format from event generators and outputs observable analysis data objects. The simulation takes into account the detector resolutions, usual reconstruction algorithms for complex objects (FastJet) and a simplified trigger emulation. Detection of very forward scattered particles relies on the transport in beamlines with the Hector software.
Machine-learning Optimized Design of Experiments
Christophe Delaere, Andrea Giammanco

We are among the founders of MODE (Machine-learning Optimized Design of Experiments,, a multi-disciplinary consortium of European and American physicists and computer scientists who target the use of differentiable programming in design optimization of detectors for particle physics applications, extending from fundamental research at accelerators, in space, and in nuclear physics and neutrino facilities, to industrial applications employing the technology of radiation detection.

We aim to develop a modular, customizable, and scalable, fully differentiable pipeline for the end-to-end optimization of articulated objective functions that model in full the true goals of experimental particle physics endeavours, to ensure optimal detector performance, analysis potential, and cost-effectiveness.
The main goal of our activities is to develop an architecture that can be adapted to the above use cases but will also be customizable to any other experimental endeavour employing particle detection at its core. We welcome suggestions, as well as interest in joining our effort, by researchers focusing on use cases for which this technology can be of benefit.

Two CP3 members currently serve as members of the MODE Supervisory Board.

External collaborators: University of Padova, INFN, Université Clermont Auvergne, Higher School of Economics of Moscow, CERN, University of Oxford, New York University, ULiege.
Search for Higgs boson(s) in CMS at the LHC in the llbb topology
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 nonresonant Higgs boson pair production in the llbb+MET final state
Christophe Delaere, 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
Christophe Delaere, 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
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
Eduardo Cortina Gil, Jérôme de Favereau, Christophe Delaere, Pavel Demin, Suat Donertas, Khawla Jaffel, Sandhya Jain, Vincent Lemaitre, 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 IRMP
All my publications on Inspire

Number of publications as IRMP member: 55
Last 5 publications


CP3-22-38: Strategies and performance of the CMS silicon tracker alignment during LHC Run~2
Tumasyan, Armen and others

[Abstract] [PDF] [Local file] [Journal] [Dial] [Full text]
Published in Nucl. Instrum. Meth. A
Refereed paper. August 12.


CP3-21-14: Advances in Multi-Variate Analysis Methods for New Physics Searches at the Large Hadron Collider
Stakia, Anna and others

[Abstract] [PDF] [Journal]
Published in Rev. Phys. 7 (2021) 100063
Refereed paper. May 18.
CP3-21-10: Toward Machine Learning Optimization of Experimental Design
MODE collaboration

[Full text]
Nuclear Physics News, 31:1 (2021), 25-28
March 31.


CP3-20-49: Search for new neutral Higgs bosons through the H$\to$ ZA $\to \ell^{+}\ell^{-} \mathrm{b\bar{b}}$ process in pp collisions at $\sqrt{s} =$ 13 TeV
Sirunyan, Albert M and others

[Abstract] [PDF] [Journal] [Dial] [Full text]
Published in JHEP 03, 2020, 055
Refereed paper. November 2.
CP3-20-37: Matrix Element Regression with Deep Neural Networks -- breaking the CPU barrier
Bury, Florian and Delaere, Christophe

[Abstract] [PDF] [Journal] [Dial]
Published in Journal of High Energy Physics volume 2021, Article number: 20 (2021)
Refereed paper. July 14.

More publications