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Accueil > Thèses, Stages, Formation et Enseignement > Propositions de thèses 2026 > Higgs physics analysis at the ATLAS experiment in view of the High Luminosity LHC phase and study and optimization of the Vertex Detector for future collider experiments
Higgs physics analysis at the ATLAS experiment in view of the High Luminosity LHC phase and study and optimization of the Vertex Detector for future collider experiments
par Tristan Beau - 10 novembre
Titre : Higgs physics analysis at the ATLAS experiment in view of the High Luminosity LHC phase and study and optimization of the Vertex Detector for future collider experiments
Directrice/directeur de thèse : G. Calderini
Groupe d’accueil : ATLAS
Webpage du projet : https://atlas.cern/
Collaboration : ATLAS
Description :
The ATLAS group at LPNHE Paris is doing research in High Energy Physics at the LHC collider at CERN and is strongly involved in the conception and development of a detector for Future Circular Collider (FCC) experiments. The group, among other activities, has a strong expertise in silicon trackers, at the basis of the ongoing construction of the upgraded Inner Tracker of the ATLAS experiment for the High Luminosity phase of the LHC (HL-LHC).
This PhD thesis subject is structured around two main physics axes :
- the study of the impact of the new ATLAS Inner tracker detector on future Higgs analyses at the High Luminosity phase of the LHC
- the development of silicon sensors for the vertex detector and the timing layers of the future FCC-ee experiments
In this Thesis work, the performance of the new inner tracker and the impact on Higgs physics at the HL-LHC is validated using processes such as the di-Higgs. While the Higgs boson has been studied in detail in many of its decay modes using the present integrated dataset collected by the ATLAS experiment, the production of two or three Higgs bosons in the same event is a rare process which cannot be analyzed in detail with the present statistics, but this will be possible with the HL-LHC dataset. This is among the few processes which allow to probe directly the self-coupling of the Higgs boson, a fundamental parameter for the study of the shape of the Higgs potential and to confirm or disprove the Standard Model nature of the Higgs. The present thesis subject will cover studies of the di-Higgs events in decay modes such as the bbtautau or the four b jets which represent some of the milestones Higgs analyses at the LHC High Luminosity phase and for which the tracking and tagging capability of the new tracker plays a major role.
This thesis work will have a second physics axis oriented to the longer-term experiments, in particular related to the Future Circular Collider FCC and the first phase of its running, based on electron-positron collisions (FCC-ee).
All current vertex detector concepts for the FCC-ee envisage the use of Monolithic Active Pixel Sensors (MAPS). These sensors integrate signal generation, amplification, and readout within a single silicon substrate, thereby simplifying the design and construction of the detectors and reducing the quantity of material crossed by particles and the power consumption. Our work focuses on the design and characterization of MAPS prototypes implemented in the 65 nm TPSCo technology, with the ultimate goal of producing a large-area, efficient, and fully functional sensor offering a spatial resolution of about few µm, suitable for operation at the FCC-ee.
A precision timing layer surrounding the tracker, with a time resolution of a few tens of picoseconds, combined with a spatial resolution of ten microns or less, is a key component of the FCC-ee concept. By exploiting time-of-flight measurements, the timing layer contributes to particle identification, an essential feature for effective flavor tagging. The excellent spatial resolution also contributes to improved momentum reconstruction of the tracks. The technologies developed by our group for the timing layer are represented by pixels sensors based on low-gain avalanche diodes (LGADs) or Monolithic Active Pixel Sensors with an additional multiplication layer to improve the timing resolution.
The PhD position offers the opportunity to work on cutting-edge technologies at the interface of instrumentation, computing, and particle physics analysis. As part of the ATLAS LPNHE group, the candidate will join international collaborations, work on front line detector R&D, and contribute to shaping the future of collider experiments.
Lieu(x) de travail : LPNHE Paris
Déplacements éventuels : CERN / DESY Hambourg
Stage proposé avant la thèse : Oui
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