Würzburg 2018 – scientific programme
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T: Fachverband Teilchenphysik
T 34: Top-Quarks: Eigenschaften I
T 34.3: Talk
Tuesday, March 20, 2018, 17:00–17:15, Z6 - SR 1.002
Direct measurement of the top-quark decay width with the ATLAS detector — •Tomas Dado1,2, Thomas Peiffer1, Arnulf Quadt1, Elizaveta Shabalina1, Philipp Stolte-Cord to Krax1, Stano Tokar2, and Royer Ticse Torres1 — 1II. Physikalisches Institut, Georg-August-Universität Göttingen — 2Comenius University in Bratislava
The top quark is the heaviest known elementary particle in the Standard Model of elementary particle physics (SM). Due to its large mass, the lifetime of the top quark is expected to be extremely short and thus, its decay width is the largest among the SM fermions. If a deviation from the predicted value is observed, the result may hint at non-SM decay channels of the top quark or non-SM top couplings.
Direct measurements of the top-quark decay width using a dataset of proton-proton collisions at a center-of-mass energy of 8 TeV and 13 TeV are discussed. Both measurements exploit the template fitting technique, where the templates for alternative top-quark decay widths are created by reweighting simulated events using theoretical Breit-Wigner distributions. The measurement at 8 TeV focuses on the single lepton channel of tt decays. Templates from two uncorrelated observables, one from the hadronic and one from the leptonic hemisphere are simultaneously fitted to data. The resulting top-quark decay width for the 8 TeV measurement is Γt = 1.76 ± 0.33 (stat.) −0.68+0.79(syst.) GeV. Status and outlook for a measurement at 13 TeV are presented. Experimental techniques for 8 TeV and 13 TeV measurements are compared.