Measurement of the charge asymmetry in highly boosted top-quark pair production in √s=8 TeV pp collision data collected by the ATLAS experiment

Abstract

In the pp →t¯tprocess 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 20.3fb−1of ppcollision data at √s=8 TeVcollected 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 (mt¯t>0.75TeV) and an absolute rapidity difference of the top and anti-top quark candidates within −2 <|yt| −|y¯t| <2is measured to be 4.2 ±3.2%, in agreement with the Standard Model prediction at next-to-leading order. A differential measurement in three t¯tmass bins is also presented.