Top quark pair property measurements using the ATLAS detector at the LHC

TL;DR

This paper presents precise measurements of top quark properties using ATLAS data at 8 TeV, including charge asymmetry, non-Standard Model decays, and spin correlations, testing the Standard Model and constraining new physics.

Contribution

It provides the first comprehensive set of measurements of top quark pair properties at 8 TeV, including charge asymmetry, rare decay searches, and spin correlation analyses.

Findings

Results agree with Standard Model predictions.

No evidence for non-SM top decays was observed.

Constraints placed on new physics models affecting top quark properties.

Abstract

Precise measurements of the properties of the top quark test the Standard Model (SM) and can be used to constrain new physics models. The top quark pair charge asymmetry is an asymmetry predicted to occur beyond leading-order QCD in the SM, and may be significantly enhanced by the presence of new physics. The $t\bar{t}$ production charge asymmetry is measured inclusively and differentially using the 8 TeV ATLAS dataset in the lepton+jets final state, including a dedicated measurement for highly boosted top quarks. The results are in agreement with the SM and compared to new physics models. The top quark is predicted in the SM to decay almost exclusively to a \textit{W} boson and \textit{b} quark. Searches for non-SM top quark decays using the 8 TeV ATLAS dataset, including $t \rightarrow qH$ and $t \rightarrow qZ$ are presented. In addition, the measurement of the spin correlations in top quark pair production using the polar angles distribution is discussed.