Measurement of the Charge Asymmetry in Highly Boosted Top-Quark Pair Production in √s̅ = 8 TeV pp Collision Data Collected by the ATLAS Experiment

In the pp → tt̅ process the angular distributions of top and anti-top quarks are expected to present a subtle difference, which could be enhanced by processes not included in the Standard Model. This Letter presents a measurement of the charge asymmetry in events where the top-quark pair is produced with a large invariant mass. The analysis is performed on 20.3 fb⁻¹ of pp collision data at √s̅ = 8 TeV collected by the ATLAS experiment at the LHC, using reconstruction techniques specifically designed for the decay topology of highly boosted top quarks. The charge asymmetry in a fiducial region with large invariant mass of the top-quark pair m{tt̅} > 0.75 TeV) and an absolute rapidity difference of the top and anti-top quark candidates within ⁻² < |y{t} - |y{t̅}| < ² is measured to be 4.2 ± 3.2% in agreement with the Standard Model prediction at next-to-leading order. A differential measurement in three tt̅ mass bins is also presented.mass bins is also presented. ⊕