Abstract
A
bstract
A search for the leptonic charge asymmetry (
A
c
ℓ
) of top-quark-antiquark pair production in association with a
W
boson (
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
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
(scale)
±
0
.
006 (MC stat.) and
−
0.063
−
0.004
+
0.007
(scale)
±
0
.
004 (MC stat.) respectively, and in agreement with the measurements.