Physique des particules (en)
cp3 |
Our group has a strong tradition of involvement in major experimental collaborations at CERN, including ALEPH, CMS, and NA62. Our contributions span the entire lifecycle of these experiments, from construction and data processing to analysis, reconstruction, and operations. This hands-on experience enables us to test and validate ideas developed within the CP3 group.
Members
Academic staff
Research scientists
Physicists, engineers and computer scientists
Postdocs
PhD students
Technical staff
Projects
Click the title to show project description.-
Software tools and data processing
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 (<latex>$tt\bar$</latex>, 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) -
Commissioning and operation of instrumentation Experimental
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. -
Data analysis Phenomenology Software tools and data processing
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.
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Computing Phenomenology Theory
CP3 is coordinating and leading the development of the MadGraph suite of tools. Tools use for the simulation of High-Energy Physics collision.
This project includes:
- NLO computation
- MadNIS: Neural Importance Sampler (AI for the phase-space integration)
- HardWare: How to port the code on modern facility (GPU, quantum computer, ...) -
We take advantage of the large statistics already recorded in Run 2 and being recorded in Run 3 by the CMS experiment to launch a systematic study of cross section, angular asymmetries and other properties in the ttW and ttH processes, which have a potentially large sensitivity to non-SM effects.
In synergy with the CP3 phenomenology group, we aim at reporting our results in a form that can be easily translated in EFT constraints. -
Data analysis Experimental
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. -
Data analysis Experimental
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. -
Data analysis Experimental
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. -
Experimental Software tools and data processing
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.
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Commissioning and operation of instrumentation Experimental Instrumentation R&D
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. -
Data analysis Experimental
The top quark, being the heaviest known elementary particle, is a powerful tool to test QCD.
The study of top quark pair production in Heavy Ion collisions at the LHC, making use of the dedicated Pb-Pb and p-Pb runs, will open a new road in the investigation of the Quark-Gluon Plasma.
This research project started with the first measurement of top-pair cross section in pp collisions at 5.02 TeV, taking advantage of a "reference run" in Nov.2015. We then update the result with a new publication making use of the larger statistics collected at the end of 2017. This measurement, in addition to being useful as a reference for measurements in Pb-Pb and p-Pb collisions at the same center-of-mass energy per nucleon, also provides a significant broadening of the lever arm for global PDF fits making use of top-quark data.
We then reported the first observation of top quark production in p-Pb collisions, using the data at 8.16 TeV taken in Nov.2016, testing the models of nuclear modification of the gluon PDF at high Bjorken-x. Finally, we provided evidence of top quark production also in Pb-Pb collisions.
We are interested in using future PbPb collision data to probe the time evolution of the QGP using top quarks.
Recent Publications
Click the title to show details.-
Colpani Serri, Alice and Flett, Chris A. and Lansberg, Jean-Philippe and Mattelaer, Olivier and Shao, Hua-Sheng and Simon, Lukas, November 7, 2025
Refereed paper. [Abstract] [PDF] [Local file] -
Céline Degrande, Matteo Maltoni, November 6, 2025
Refereed paper. [Abstract] [PDF] [Local file] -
Hayrapetyan, Aram and others, September 22, 2025
Refereed paper. [Abstract] [PDF] [Local file] [Journal] [Dial] -
Dorukhan Boncukcu, (Istanbul Tech. U.); Acelya Deniz Gungordu; Samuel Louis Bein (Louvain U.); Kevin Pedro (Fermilab) ; Moritz Wolf (Hamburg U.); Ekim Vural, Cakir, Altan Muammer (Istanbul Tech. U.), July 2, 2025
Contribution to proceedings. [Local file] [Full text]