Direct top-quark decay width measurement in the t t ¯ lepton+jets channel at s = 8 TeV with the ATLAS experiment

Abstract

This paper presents a direct measurement of the decay width of the top quark using $t\overline{t}$ events in the lepton+jets final state. The data sample was collected by the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 8 TeV and corresponds to an integrated luminosity of 20.2 fb ${}^{-1}$ . The decay width of the top quark is measured using a template fit to distributions of kinematic observables associated with the hadronically and semileptonically decaying top quarks. The result, ${\Gamma }_t=1.76\pm 0.33\left(\text{stat.}\right){}_{-0.68}^{+0.79}\left(\text{syst.}\right)\text{GeV}$ for a top-quark mass of 172.5 GeV, is consistent with the prediction of the Standard Model.