Probing the top-quark width through ratios of resonance contributions of $e^+e^-\rightarrow W^+W^-b\bar{b}$

TL;DR

This paper proposes a method to measure the top-quark width at electron-positron colliders by analyzing ratios of offshell to onshell regions in the $e^+e^- o W^+W^-bar{b}$ process, which are insensitive to certain couplings.

Contribution

It introduces a novel approach using offshell region ratios in $e^+e^-$ collisions to determine the top-quark width independently of the $g_{tbW}$ coupling.

Findings

Ratios are sensitive to the top-quark width.

Method is effective at different energies and polarizations.

Potential application at the LHC discussed.

Abstract

We exploit offshell regions in the process $e^+e^-\rightarrow W^+W^-b\bar{b}$ to gain access to the top-quark width. Working at next-to-leading order in QCD we show that carefully selected ratios of offshell regions to onshell regions in the reconstructed top and antitop invariant mass spectra are, \emph{independently} of the coupling $g_{tbW}$, sensitive to the top-quark width. We explore this approach for different centre of mass energies and initial-state beam polarisations at $e^+e^-$ colliders and briefly comment on the applicability of this method for a measurement of the top-quark width at the LHC.