Study of the underlying event in top quark pair production in pp collisions at 13 TeV

TL;DR

This paper presents the first measurements of the underlying event in top quark pair production at 13 TeV, analyzing charged-particle tracks to understand event properties and test universality at high energy scales.

Contribution

It provides the first characterization of the underlying event in top quark pair production at 13 TeV, using CMS data and differential cross sections.

Findings

No deviation from universality hypothesis at high energy scales.

First measurement of underlying event properties in top quark pairs.

Differential cross sections as functions of multiplicity and kinematic variables.

Abstract

Measurements of normalized differential cross sections as functions of the multiplicity and kinematic variables of charged-particle tracks from the underlying event in top quark and antiquark pair production are presented. The measurements are performed in proton-proton collisions at a center-of-mass energy of 13 TeV, and are based on data collected by the CMS experiment at the LHC in 2016 corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Events containing one electron, one muon, and two jets from the hadronization and fragmentation of b quarks are used. These measurements characterize, for the first time, properties of the underlying event in top quark pair production and show no deviation from the universality hypothesis at energy scales typically above twice the top quark mass.