ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2016). Measurement of the charge asymmetry in highly boosted top-quark pair production in root s=8 TeV pp collision data collected by the ATLAS experiment. Phys. Lett. B, 756, 52–71.
Abstract: In the pp -> t (t) over bar 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 root s=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(t (t) over bar) > 0.75 TeV) and an absolute rapidity difference of the top and anti-top quark candidates within -2 vertical bar y(t)vertical bar – vertical bar y(<(t) over bar)vertical bar < 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)over bar> mass bins is also presented.
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