Differential measurement of $\mathrm{t}\bar{\mathrm{t}}\mathrm{Z}$ production at $\sqrt{s}=13\,\mathrm{TeV}$ with the CMS experiment

TL;DR

This paper presents the first differential measurement of top quark pair production with a Z boson at 13 TeV, testing the Standard Model and constraining anomalous couplings using CMS data.

Contribution

It introduces a novel differential measurement of t-tbar-Z production, analyzing key kinematic variables with CMS data from 2016-2017.

Findings

Measured differential cross sections as functions of Z boson pT and decay angles.

Results agree with state-of-the-art theoretical predictions.

Provides constraints on anomalous top-Z couplings.

Abstract

Measurements of top quark pair production in association with a Z boson ($\mathrm{t}\bar{\mathrm{t}}\mathrm{Z}$) provide direct tests of the coupling of top quarks and Z bosons, as well as the description of the production mechanism in QCD. The measurements can be used to constrain possible contributions from anomalous top quark-Z boson couplings. A first differential $\mathrm{t}\bar{\mathrm{t}}\mathrm{Z}$ production measurement has been performed by the CMS experiment using events with three leptons collected in 2016 & 2017. The differential cross sections are reported as functions of the Z boson transverse momentum, and of the angle between the Z boson and one of its decay leptons, boosted to the Z boson's rest frame. The results are compared to state-of-the-art theory predictions.