# Observation of the associated production of a top quark and a Z boson in pp collisions at √s = 13 TeV with the ATLAS detector

Collaboration, ATLAS
(2020) Observation of the associated production of a top quark and a Z boson in pp collisions at √s = 13 TeV with the ATLAS detector. The Journal of High Energy Physics.

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## Abstract

Single top-quark production in association with a Z boson, where the Z boson decays to a pair of charged leptons, is measured in the trilepton channel. The proton-proton collision data collected by the ATLAS experiment from 2015 to 2018 at a centre-of-mass energy of 13 TeV are used, corresponding to an integrated luminosity of 139 fb−1. Events containing three isolated charged leptons (electrons or muons) and two or three jets, one of which is identified as containing a b-hadron, are selected. The main backgrounds are from tt¯Z and diboson production. Neural networks are used to improve the background rejection and extract the signal. The measured cross-section for tℓ+ℓ−q production, including non-resonant dilepton pairs with mℓ+ℓ−> 30 GeV, is 97 ± 13 (stat.) ± 7 (syst.) fb, consistent with the Standard Model prediction.

Item Type: Article Comments: 44 pages in total, author list starting page 28, 6 figures, 4 tables, submitted to JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2018-01/ hep-ex, hep-ex Symplectic Admin 10 Aug 2020 08:03 17 May 2021 11:36 10.1107/JHEP07(2020)124 https://link.springer.com/article/10.1007%2FJHEP07... https://livrepository.liverpool.ac.uk/id/eprint/3096807