ATLAS and CMS measurements of the $t\bar{t}$ cross section, including off-shell and near threshold

TL;DR

This paper reviews recent ATLAS and CMS measurements of the top-antitop cross section, including off-shell effects, threshold phenomena, and potential quasi-bound state formation, highlighting new insights into top quark properties.

Contribution

It presents new measurements of the $t\bar{t}$ cross section, explores off-shell effects, and discusses the observation of an excess near threshold indicating possible quasi-bound states.

Findings

Off-shell effects are probed in specific processes.

An excess of events near the top pair threshold is observed.

An indirect extraction of the top quark Yukawa coupling is reviewed.

Abstract

Recent measurements of the $t\bar{t}$ cross section, performed both inclusively and differentially by the ATLAS and CMS Collaborations, are reported. In particular, off-shell effects are probed in the $pp\to W^+bW^-\bar{b}$ and $pp\to e^\pm\mu^\mp +b\bar{b}$ processes, and modelling aspects of the POWHEG bb4$\ell$ Monte Carlo generator are discussed. Cross section and properties measurements are also performed at the threshold: we review an indirect extraction of the top quark Yukawa coupling, as well as the recent observations by both experiments of an excess of events near the top pair production threshold that is consistent with the formation of quasi-bound states.