Measurements of the inclusive and differential production cross sections of a top-quark–antiquark pair in association with a Z boson at $$\sqrt{s} = 13$$ s = 13 TeV with the ATLAS detector

Abstract

Abstract Measurements of both the inclusive and differential production cross sections of a top-quark–antiquark pair in association with a Z boson (

$$t{\bar{t}}Z$$

t

t

¯

Z

) are presented. The measurements are performed by targeting final states with three or four isolated leptons (electrons or muons) and are based on

$$\sqrt{s} = 13$$

s

= 13

TeV proton–proton collision data with an integrated luminosity of 139

$$\hbox {fb}^{-1}$$

fb

- 1

, recorded from 2015 to 2018 with the ATLAS detector at the CERN Large Hadron Collider. The inclusive cross section is measured to be

$$\sigma _{t{\bar{t}}Z} = 0.99 \pm 0.05$$

σ

t

t

¯

Z

= 0.99 ± 0.05

(stat.)

$$\pm \, 0.08$$

±

0.08

(syst.) pb, in agreement with the most precise theoretical predictions. The differential measurements are presented as a function of a number of kinematic variables which probe the kinematics of the

$$t{\bar{t}}Z$$

t

t

¯

Z

system. Both absolute and normalised differential cross-section measurements are performed at particle and parton levels for specific fiducial volumes and are compared with theoretical predictions at different levels of precision, based on a

$$\chi ^{2}/$$

χ 2

/

ndf and p value computation. Overall, good agreement is observed between the unfolded data and the predictions.