Séminaires
Séminaire étudiants (fin de la première année)
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Europe/Paris
Amphiteatre (CPPM)
Amphiteatre
CPPM
Description
Pierre Li Cavoli
"Theoretical and experimental studies of the impact of Single Event Effect induced by atmospheric muons of nanoscales CMOS technologies"
Since the technological roadmap tend to shrink the dimensions of the transistors from the micrometric to the nanometric scales, the sensitivity thresholds of electronic circuits has increased. Thus more and more effects due to SEE appear in electronic devices. Among the encountered problems, those created by cosmic radiations are significant. Recent researches have demonstrated the occurrence of soft errors due to protons and to muons. Multiphysics modeling based on MonteCarlo simulations, allow to characterize the interaction between muons and semiconductors by modeling the radiation field, the generation of electronhole pairs in the semiconductor, the charge transport and collection, and the circuit electrical response. This kind of model has to be adjusted by experimental measures. In order to do that, the metrology of the muon environment is necessary. By its depth, the Laboratoire Souterrain Bas Bruit's facility cuts the proton and neutron contributions.
Thus it allows us to only measure the muon flux by using detectors (CCDcamera and scintillators). The aim of this PhD is to investigate the atmospheric muon effects along the scaling trend of CMOS technologies by using a modelisation software as GEANT4 in order to simulate the interaction between atmospheric muons and semiconductors.
Royer Edson Ticse Torres
"Tagging jets with double B-hadron using multiple secondary vertices"
Following the discovery of the Higgs boson in July 2012, further data will allow in-depth investigation of the boson's properties. The associated production of a Higgs boson with top quarks will be accessible for the first time after the LHC upgrade in 2015 and will be the subject of my PhD thesis. The search for the Higgs boson in the associated production with two top quarks, with the Higgs decaying in two b quarks(pp→ttH (H→bb)) have as dominant background: ttbb, where the b-quark pair are merge in a same jet. Thus, a tool for identification of jets containing two b quarks will be used to control the dominant background (ttbb production).
The most advanced ATLAS b-tagging algorithms do not provide information on the number of b-quark within the jet. I use multi secondary vertex finder(MSV) to reconstruct multiple vertices within jet then I developed a multivariate analysis (Boosted Decision Tree) to increase the discrimination power between jet with two b hadrons from single b jets, c jets and light jets. I developed two versions of double b-hadron tagger using multi-vertexing properties. As a part of this work, several studies have been done to determine a good set of input variables to train a BDT.
Sébastien Kahn
"Optimization of the electron identification criterion for the 2015 ATLAS data taking at high pile-up configuration"
The Large Hadron Collider will resume data taking in spring 2015, with a proton-proton collision center of mass energy increased to 13 TeV and at higher luminosity. The first part of my PhD work was to adapt the online and offline electron identification criteria to these new data taking conditions, in particular the increased pile-up level ( ~x2 ). The main challenges were to maintain good online/offline performances ( electron efficiency/ jet rejection) within a limited trigger bandwidth. And to keep have a good stability with respect to pile-up and robustness with espect to potential initial detector mis-alignments. I will show how this has been achieved, providing a single electron trigger menu and a full set of offline identification menus adapted to the need of the physics analyses.