Measurement of the charge asymmetry in dileptonic decays of top quark pairs in proton-proton collisions at 7 TeV using the ATLAS detector

TL;DR

This paper reports a measurement of the top-antitop charge asymmetry in dileptonic decays at 7 TeV using ATLAS data, finding results consistent with Standard Model predictions.

Contribution

First measurement of top-antitop charge asymmetry in dileptonic channel at 7 TeV with two different observables using ATLAS data.

Findings

Measured asymmetries are consistent with Standard Model.

Results show no significant deviation from predictions.

Analysis techniques for dileptonic top pair decays are validated.

Abstract

A measurement of the top--antitop ($t\bar{t}$) charge asymmetry is presented using 2011 LHC data collected by the ATLAS detector corresponding to an integrated luminosity of 4.6 fb$^{-1}$ at a centre-of-mass energy of 7 TeV. The analysis is performed in the dilepton channel, and two different observables are studied: $A^{\ell\ell}_{\mathrm{C}}$, based on the identified charged leptons, and $A^{t\bar{t}}_{\mathrm{C}}$, based on the reconstructed $t\bar{t}$ final state. The asymmetries, measured to be $A^{\ell\ell}_{\mathrm{C}} = 0.024 \pm 0.015 \mathrm{(stat.)} \pm 0.009 \mathrm{(syst.)}$ and $A^{t\bar{t}}_{\mathrm{C}} = 0.021 \pm 0.025 \mathrm{(stat.)} \pm 0.017 \mathrm{(syst.)}$, are in agreement with the Standard Model predictions.