Inclusive and differential measurements of the t t-bar charge asymmetry in pp collisions at sqrt(s) = 8 TeV

TL;DR

This paper reports on measurements of the t t-bar charge asymmetry in proton-proton collisions at 8 TeV using CMS data, including inclusive and differential analyses, with results consistent with the Standard Model predictions.

Contribution

First measurement of t t-bar charge asymmetry in a reduced fiducial phase space at the LHC, providing new insights into top quark pair production asymmetries.

Findings

Inclusive asymmetry near zero with uncertainties

Differential asymmetries as functions of rapidity, transverse momentum, and invariant mass

Results consistent with Standard Model predictions within two standard deviations

Abstract

The t t-bar charge asymmetry is measured in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data, collected with the CMS experiment at the LHC, correspond to an integrated luminosity of 19.7 inverse femtobarns. Selected events contain an electron or a muon and four or more jets, where at least one jet is identified as originating from b-quark hadronization. The inclusive charge asymmetry is found to be 0.0010 +/- 0.0068 (stat) +/- 0.0037 (syst). In addition, differential charge asymmetries as a function of rapidity, transverse momentum, and invariant mass of the t t-bar system are studied. For the first time at the LHC, the measurements are also performed in a reduced fiducial phase space of top quark pair production, with an integrated result of -0.0035 +/- 0.0072 (stat) +/- 0.0031 (syst). All measurements are consistent within two standard deviations with zero asymmetry as well as with the predictions of the standard model.