2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/219686In this talk, I review the effective theory approach to unstable particle production and present results of a calculation of the process e- e+ ->mu- nubar_mu u dbar X near the W-pair production threshold up to next-to-leading order in GammaW/MW ~ alpha ~ v^2. The remaining theoretical uncertainty and the impact on the measurement of the W mass is discussed.7 pages (ilcws07.cls included), to appear in the proceedings of the International Linear Collider Workshop (LCWS/ILC07), 30 May - 3 Jun 2007, Hamburg, GermanyHigh Energy Physics - Phenomenologytext