PARTICLES NEAR-THRESHOLD

We propose returning to the definition of the width of a particle in t erms of the pole in the particle's propagator. Away from thresholds, t his definition of width is equivalent to the standard perturbative def inition, up to next-to-leading order; however, near a threshold, the t wo definitions differ significantly. The width as defined by the pole position provides more information in the threshold region than the st andard perturbative definition and, in contrast with the perturbative definition, does not vanish when a two-particle s-wave threshold is ap proached from below.