Measurement of the charge asymmetry in top-quark pair production in proton-proton collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports a measurement of the charge asymmetry in top-quark pair production at 7 TeV proton-proton collisions, finding results consistent with the Standard Model predictions within uncertainties.

Contribution

First measurement of the charge asymmetry in top-quark pairs at 7 TeV using CMS data, employing two variables based on top quark pseudorapidities and rapidities.

Findings

Measured asymmetries are consistent with Standard Model predictions.

Results: A[C,eta] = -0.017 +/- 0.032 (stat.) +0.025/-0.036 (syst.)

Results: A[C,y] = -0.013 +/- 0.028 (stat.) +0.029/-0.031 (syst.)

Abstract

The difference in angular distributions between top quarks and antiquarks, commonly referred to as the charge asymmetry, is measured in pp collisions at the LHC with the CMS experiment. The data sample corresponds to an integrated luminosity of 1.09 inverse femtobarns at a centre-of-mass energy of 7 TeV. Top-quark pairs are selected in the final state with an electron or muon and four or more jets. At least one jet is identified as originating from b-quark hadronization. The charge asymmetry is measured in two variables, one based on the pseudorapidities (eta) of the top quarks and the other on their rapidities (y). The results A[C,eta] = -0.017 +/- 0.032 (stat.) + [+0.025/-0.036] (syst.) and A[C,y] = -0.013 +/- 0.028 (stat.) + [+0.029/-0.031] (syst.) are consistent within uncertainties with the standard-model predictions.