Probing the top-quark width through ratios of resonance contributions of e + e − → W + W − b b ¯ $$ {mathrm{e}}^{+}{mathrm{e}}^{-}to {mathrm{W}}^{+}{mathrm{W}}^{-}mathrm{b}overline{mathrm{b}} $$

In this paper we propose a method to gain access to the top-quark width which exploits off-shell regions in the process $$ {e}^{+}{e}^{-}to {w}^{+}{w}^{-}boverline{b} $$ . working at next-to-leading order in qcd we show that carefully selected ratios of off-shell regions to on-shell regions in the reconstructed top and anti-top invariant mass spectra are, 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.