Unit:
Κατεύθυνση Πυρηνική Φυσική και Φυσική Στοιχειωδών ΣωματιδίωνLibrary of the School of Science
Supervisors info:
Νίκη Σαουλίδου, Αναπληρώτρια καθηγήτρια , τμήμα Φυσικής, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Original Title:
Μελέτες πολυμεταβλητών αναλυτών με πραγματικά δεδομένα και δεδομένα προσομοίωσης για την διαδικασία ttH, H->bbbar στο διλεπτονικό κανάλι με το πείραμα CMS στον LHC του CERN
Translated title:
Development and studies of Multivariate Analyzers with real and simulated data for the ttH, H->bbbar process in the dileptonic final state with the CMS Experiment at the CERN LHC
Summary:
The Large Hadron Collider (LHC) at the CERN laboratory provides proton-proton collisions at 13 TeV, the highest energy to date, enabling experiments to investigate the Standard Model of physics (SM) with great accuracy. The discovery of the Higgs boson (July 4, 2012) confirmed the existence of a mechanism that gives mass to particles. The coupling constant of the Higgs' particle with fermions, which is proportional to the mass of the fermion, prompts us to study its coupling with the heaviest fermion of SM, the top quark. In the present work, the associated production of Higgs boson with a top quark - antiquark pair (ttH), with Higgs finally decaying into a bbbar pair and both top quarks decaying into leptons, is being studied. The purpose of this work is the improvement in the significance of the measurements, namely the detection of the signal over the expected background. The "Tag Rate Function" (TRF) method of a data driven prediction for the main ttbar + jets background, namely TRF, is being reviewed. The method is then verified in the real datasets, and the agreement between real and simulation data is also examined. Finally, a new Artificial Neural Network is developed, which can be used as an additional pre-selection criterion for the signal separation over the background and increases the significance of the measurement by a large factor. The Neural Network's training occurs via enriched data statistics, applying the weights produced by the TRF method. Finally the performance of the overall analysis in the near (Run III) and longer term (HL-LHC) future is being briefly presented.
Main subject category:
Science
Keywords:
High Energy Physics, CMS Experiment, LHC, CERN, Higgs Particle, ttH dilepton channel
