Measurement of the <em>tZq</em> differential cross-section with the ATLAS detector at the LHC

Abstract

The production of a top quark in association with a Z boson is studied using proton-proton collision data collected by the ATLAS detector at the LHC during 2015 to 2018 at a centre of mass energy of 13 TeV. The differential cross-sections are measured in the trilepton decay channel, in which both the top quark and the Z boson decay into final states involving charged leptons. Events containing three leptons (electron and/or muon), 2-5 jets out of which 1-2 are identified as b-quark jets are selected. Dominant background processes include Z+ jets, ttZ and diboson production. The technique of profile likelihood unfolding (PLU) is implemented for the measurement. Various validation tests are performed before unfolding real data. This measurement is the first differential cross-section measurement of the <em>tZq</em> production within the ATLAS collaboration. The result is in agreement with the Standard Model prediction.