Cross section measurement of tttt production and its sensitivity to the CP property of the top-Higgs Yukawa coupling with the ATLAS detector

  • Martin Murin

Student thesis: Phd

Abstract

This thesis presents a measurement of the \tttt production cross section using proton-proton collision data at a centre-of-mass energy of 13~TeV. The data was collected by the ATLAS detector at the Large Hadron Collider corresponding to an integrated luminosity of $139~\ifb$. The measurement uses events containing exactly one or two leptons ($e$ or $\mu$) with opposite electric charges. The events are categorised based on the number of jets and their likelihood to contain $b$-hadrons. A multivariate technique is used to discriminate between the signal and background events. The measured \tttt production cross section is $\sigma_{\tttt}=26^{+17}_{-15}\ \mathrm{fb}$, with a corresponding observed (expected) significance of 1.9 (1.0) standard deviations over the background-only hypothesis. The result is combined with a measurement performed using events with two same-sign leptons and at least three leptons. The combination yields an observed (expected) significance of 4.7 (2.6) standard deviations against the background-only prediction, with a measured cross section of $\sigma_{\tttt}=24^{+7}_{-6}\ \mathrm{fb}$. Both results are consistent with the SM prediction within 2 standard deviations.
Date of Award31 Dec 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorAndrew Pilkington (Supervisor) & Yvonne Peters (Supervisor)

Keywords

  • CP
  • Yukawa coupling
  • four top
  • Higgs boson
  • top quark

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