Measurement of lepton differential distributions and the top quark mass in $t\bar{t}$ production in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

TL;DR

This paper measures lepton and top quark distributions in top-antitop events at 8 TeV with the ATLAS detector, compares results to theoretical models, and determines the top quark pole mass with high precision.

Contribution

It provides detailed differential cross-section measurements in dileptonic top pair production and extracts the top quark pole mass from these distributions, enhancing understanding of top quark properties.

Findings

Measured differential cross-sections in dileptonic $t\bar{t}$ events.

Compared measurements with Monte Carlo and QCD predictions.

Determined the top quark pole mass as 173.2 GeV with combined uncertainties.

Abstract

This paper presents single lepton and dilepton kinematic distributions measured in dileptonic $t\bar{t}$ events produced in 20.2 fb$^{-1}$ of $\sqrt{s}=8$ TeV $pp$ collisions recorded by the ATLAS experiment at the LHC. Both absolute and normalised differential cross-sections are measured, using events with an opposite-charge $e\mu$ pair and one or two $b$-tagged jets. The cross-sections are measured in a fiducial region corresponding to the detector acceptance for leptons, and are compared to the predictions from a variety of Monte Carlo event generators, as well as fixed-order QCD calculations, exploring the sensitivity of the cross-sections to the gluon parton distribution function. Some of the distributions are also sensitive to the top quark pole mass; a combined fit of NLO fixed-order predictions to all the measured distributions yields a top quark mass value of $m_t^{\rm pole}=173.2\pm 0.9\pm0.8\pm1.2$ GeV, where the three uncertainties arise from data statistics, experimental systematics, and theoretical sources.