A Direct Measurement of the Total Decay Width of the Top Quark

TL;DR

This paper reports the most precise direct measurement of the top quark's total decay width using Tevatron data, reconstructing top and W boson masses to compare with simulations and extract the width.

Contribution

It introduces a novel analysis method combining mass reconstruction and in-situ calibration to measure the top quark width directly from collider data.

Findings

Measured top-quark width consistent with Standard Model

Established the most precise direct measurement to date

Constrained the width to 1.10-4.05 GeV at 68% CL

Abstract

We present a measurement of the total decay width of the top quark using events with top-antitop-quark pair candidates reconstructed in the final state with one charged lepton and four or more hadronic jets. We use the full Tevatron Run II data set of $\sqrt{s} = 1.96$ TeV proton-antiproton collisions recorded by the CDF II detector. The top-quark mass and the mass of the hadronically-decaying $W$ boson are reconstructed for each event and compared with distributions derived from simulated signal and background samples to extract the top-quark width (\gmt) and the energy scale of the calorimeter jets with {\it in-situ} calibration. For a top-quark mass $\mtop = \gevcc{172.5}$, we find $1.10<\gmt<\gev{4.05}$ at 68% confidence level, which is in agreement with the standard-model expectation of \gev{1.3} and is the most precise direct measurement of the top-quark width to date.