Using Bottom-Quark Hadrons from Top-Quark Decays at the ATLAS Detector to Measure Charge Parity Violation and Explore Lepton Flavour Universality Violation

Abstract

Charge and CP-violation asymmetries are measured in lepton+jets $t\overline{t}$ events using \mbox{$\sqrt{s}=$\SI{13}{\tera\electronvolt}} centre-of-mass energy proton-proton collisions from Run 2 of the ATLAS detector at the LHC, with an integrated luminosity of \SI{140}{\per\femto\barn}. These charge asymmetries are extracted using soft muons from the semileptonic decays of $b$-hadrons and prompt leptons from top-quark decays. Using $b$-hadron decay chain fractions, these charge asymmetries are linked to four CP-violation asymmetries, which are compared with results from other experiments and the Standard Model predictions. Alongside this measurement, a feasibility study is presented, investigating the possibility of using soft muons to make a measurement of Lepton Flavour Universality Violation