Direct top-quark decay width measurement in the tt ̄ 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 tt ̄ events in the lep- ton+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 distribu- tions of kinematic observables associated with the hadroni- cally and semileptonically decaying top quarks. The result, Γt = 1.76 ± 0.33 (stat.) +0.79 −0.68 (syst.) GeV for a top-quark mass of 172.5 GeV, is consistent with the prediction of the Standard Model.