Search for leptonic charge asymmetry in tt¯ W production in final states with three leptons at √s = 13 TeV

Abstract

Abstract A search for the leptonic charge asymmetry ($$ {A}_{\textrm{c}}^{\ell } $$ A c ℓ

) of top-quark-antiquark pair production in association with a W boson ($$ t\overline{t}W $$ t

t ¯

W ) is presented. The search is performed using final states with exactly three charged light leptons (electrons or muons) and is based on $$ \sqrt{s} $$

s

= 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN during the years 2015–2018, corresponding to an integrated luminosity of 139 fb−1. A profile-likelihood fit to the event yields in multiple regions corresponding to positive and negative differences between the pseudorapidities of the charged leptons from top-quark and top-antiquark decays is used to extract the charge asymmetry. At reconstruction level, the asymmetry is found to be −0.12 ± 0.14 (stat.) ± 0.05 (syst.). An unfolding procedure is applied to convert the result at reconstruction level into a charge-asymmetry value in a fiducial volume at particle level with the result of −0.11 ± 0.17 (stat.) ± 0.05 (syst.). The Standard Model expectations for these two observables are calculated using Monte Carlo simulations with next-to-leading-order plus parton shower precision in quantum chromodynamics and including next-to-leading-order electroweak corrections. They are $$ -{0.084}_{-0.003}^{+0.005} $$ −

0.084

− 0.003

+ 0.005

(scale) ± 0.006 (MC stat.) and $$ -{0.063}_{-0.004}^{+0.007} $$ −

0.063

− 0.004

+ 0.007

(scale) ± 0.004 (MC stat.) respectively, and in agreement with the measurements.