Direct top-quark decay width measurement in the t(t)over-bar lepton plus jets channel at root s=8 TeV with the ATLAS experiment

Abstract

This paper presents a direct measurement of the decay width of the top quark using

t

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,

Γ t

= 1.76 ± 0.33

( stat. )

- 0.68

+ 0.79

( syst. )

GeV

for a top-quark mass of 172.5 GeV, is consistent with the prediction of the Standard Model.