2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/193123In the framework of effective field theory we show that, at two-loop order, the mass and width of the Δresonance defined via the (relativistic) Breit-Wigner parametrization both depend on the choice of field variables. In contrast, the complex-valued position of the pole of the propagator is independent of this choice.3 pages, 1 figure, REVTeX 4High Energy Physics - Phenomenologytext