Description of the thesis topic

Heterogeneous computing for the HL-LHC and quark top and Higgs boson physics with CMS at the LHC

The CCLab team at the Centre de Calcul de l'IN2P3 (CC-IN2P3) and the CMS group at the Institut de Physique des 2 Infinis de Lyon (IP2I) are inviting applications for a PhD student position in particle physics. The subject of the thesis is twofold: firstly, the analysis of data from the CMS experiment at the LHC in the top-Higgs sector, and secondly, the development of CMS reconstruction software based on a heterogeneous computing architecture.

Work Context

The Centre de Calcul de l'Institut national de physique nucléaire et de physique des particules (CC-IN2P3) is a support and research unit of the CNRS. It is involved in about fifty international experiments, and plays a key role in the data management of the major physics experiment. In particular, it is one of the 14 main international data processing centers for experiments at CERN's LHC accelerator. It also provides computing resources for the VIRGO gravitational wave experiment. Future challenges for CC-IN2P3 include data processing for the future High Luminosity LHC project at CERN, the new SPIRAL 2 particle gas pedal at GANIL, the BELLE II detector in Japan, as well as promising astroparticle physics projects such as the future LSST telescope, and the European EUCLID satellite.

The Institut de Physique des 2 Infinis (IP2I) is a joint research unit (UMR 5822) of CNRS/IN2P3 and Université Claude Bernard Lyon 1 (UCBL). IP2I is a founding member of CMS and played a key role in the development, installation and commissioning of the electromagnetic calorimeter and tracker detectors. The group has also made important contributions in the fields of top quark physics (top mass measurements, top-antitop resonance searches, vector-like top searches and Lorentz invariance breaks, etc.), and Higgs boson searches and measurements (two-photon decay channel, HH, top-Higgs coupling). In addition, the group has major responsibilities in the effort to improve CMS for the HL-LHC (future outer tracker and improved muon RPC).

The CMS experiment is a multi-purpose detector at the LHC proton-proton collider at CERN. It has a vast physics programme ranging from the study of the Standard Model (including the Higgs boson) to the search for extra dimensions and particles that could make up dark matter. In 2022, the CMS restarted the data taking with the beginning of the Run 3 of the LHC. The Run 3 data, which will be collected until the end of 2025, will form the basis of the thesis analysis.
The successful candidate will play an active role in the analysis of the multilepton ttH final state measurement. The aim is to search for CP violation in the Yukawa coupling of the top quark to the Higgs boson, in order to contribute to the understanding of the asymmetry between matter and antimatter observed in the universe.


In parallel with the physics analysis, the PhD student will be working with the CCLab team on the development of CMS software for offline data reconstruction. This will involve rewriting new reconstruction algorithms so that they can be run on heterogeneous platforms, i.e. systems where a traditional processor (CPU) is coupled with an accelerator (e.g. a GPU). The PhD student will therefore gain experience in writing and developing algorithms for parallel computing, which will be of the utmost importance for the HL-LHC: one of CMS's key objectives is to have 80% of the reconstruction software running on heterogeneous architectures by Run 5. The successful candidate will develop algorithms for the reconstruction of the tracker detector and the muon system, exploring in particular the possibilities of extending this approach to other detector and experiment geometries.

Additional Information

Candidates must hold a master's degree in physics or be about to obtain one. A good knowledge of particle physics, mathematical methods of data analysis and computer programming is required.

The position is funded by CNRS-IN2P3 for three years. The successful candidate will be enrolled in the "Physics and Astrophysics" doctoral school (ED-HAST) at the University of Lyon, and will travel regularly to CERN.

Applications must include a statement of interest (1 page), a CV (2 pages maximum), two letters of recommendation and, if already available, (preliminary) Master's grades.

The statement of interest, CV and grades should be submitted via the CNRS portal. Letters of reference should be sent to Adriano Di Florio (adriano.di.florio@cern.ch) and before the application deadline. The appointment will start on October 1, 2024.