On the definition of the Δmass and width

Abstract

In 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 4