Projet de thèse en Physique Subatomique et Astroparticules
Sous la direction de Tetiana Berger-hryn'ova.
Le projet de thèse consiste en une recherche de nouveau phénomène dans l'état final e+e- avec les données du Run2 du LHC á l'experiment ATLAS.
A resonance search in the e+e- final state with the Run 2 LHC data with the ATLAS experiment and ATLAS Liquid Argon Calorimeter upgrade
This PhD proposal is focused on the searches for new phenomena in the dilepton final state in protonproton collisions with the ATLAS experiment at the LHC at CERN. This analysis was one of the main searches of the ATLAS experiment in Run 1, and presents renewed interest in Run 2 due to the increase of the center-of-mass energy to 13TeV. Full Run 2 dataset (2015-2018) will provide an opportunity to extend the discovery reach in this channel up to a mass of nearly 4TeV. Many aspects of this analysis such as electron efficiency measurements and background estimation are still being reviewed in the view of much higher electron energy reach in the Run 2 data. In addition to the above a range of long-term analysis improvements will be investigated to increase potential discovery significance: e.g. the lower dielectron mass region contains a lot of background events, thus it is possible to find a functional shape which describes this smooth background in data and to search for a resonance structures on top of it (similarly to the work done in LAPP for ATLAS Collaboration, Phys. Lett. B 716 (2012) 1-29). To further maximize the statistical significance of the discovery over the full search mass range it is possible to introduce electron categories in which events are split according to the electron resolution (barrel and endcap). Neither of those two proposals has been yet studied in the context of the ATLAS exotics dilepton search and the expected rate of incoming data in Run 2 makes improvements of this kind very interesting. This work will benefit from and contribute to the strong electron reconstruction expertise already available at LAPP. We collaborate with theorists from University of Granada on the model-independent interpretation of the results. A part of the thesis work is expected to be on development towards the upgrade of the liquid argon calorimeter trigger electronics upgrade. The goal is to design and install the new trigger readout electronics allowing for higher-granularity, higher-resolution and longitudinal shower information at the first level of the calorimeter trigger. The new electronics will be installed in ATLAS during the second long shutdown of the LHC in 2019 and 2020, but a demonstrator system have been installed on the ATLAS detector since the beginning of Run 2. This upgrade will improve the trigger energy resolution and efficiency for all objects based on calorimeter information while enhancing discrimination against backgrounds and fakes in an environment with high instantaneous luminosity. The LAPP team is engaged in the construction of high speed and high bandwidth digital electronics which will allows to deliver fully calibrated transverse energy to the first level of the calorimeter trigger. Among other tasks, student will participate in the tests of the demonstrator system and the analysis of data collected with it.