Phenomenology of searches for new neutral resonances in top quark pair production at the LHC

Abstract

This report presents the research that I have done in conjunction with my supervisors Lucio Cerrito and Stefano Moretti, as well as in collaboration with Francesco Spanò, over the last three years of my studies. Chapter 6 presents work conducted as part of the e/ signature trigger group within the ATLAS collaboration. Chapter 7 presents work released in a publicly available paper, while the study discussed in chapter 8 I hope to be the subject of an upcoming publication.

This thesis presents two studies considering new neutral resonances in top quark pair production at the Large Hadron Collider. Its focus is largely on charge and spin asymmetry observables sensitive to the chiral couplings of a Z′ boson. Both analyses employ a 2 ! 6 simulation accounting for all possible leading order topologies for both signal and (irreducible) top backgrounds including interference effects. The first is a parton-level analysis aimed at the lepton-plus-jets final state, using a reconstruction procedure of the (anti)top quark mass and momenta that closely mimics experimental conditions. Results show the potential of these observables to characterise the chiral couplings of
the Z′ boson and distinguish between different theoretical models, and to improve the discovery potential in combination with the tt differential cross section. The second study extends to an analysis using the dilepton final state in top pair production to observe a new resonance, accounting for parton-shower, hadronisation and simulated reconstruction with the ATLAS detector. Several approaches to top reconstruction and their relative observational power are explored. Finally a study of the sources for single electron trigger inefficiencies with the ATLAS detector is presented.

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Identifiers

ORCID for Stefano Moretti: orcid.org/0000-0002-8601-7246

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