For a stable particle represented by an isolated propagator pole, the pole mass is defined by the pole at invariant momentum squared . It is a property of the complete propagator pole, distinct from an arbitrary running mass parameter defined in a renormalization scheme.
An unstable resonance generally has a complex pole, often parametrized as ; its real mass and width conventions must then be specified. A peak position in a measured distribution need not coincide exactly with that pole parameter because of backgrounds, thresholds and resolution. Confined fields or infrared-singular charged states require further qualifications before the simple isolated stable-particle picture applies. The pole location and the chosen field's pole residue are different quantities.
Articles by others on the same topic
The term "pole mass" is commonly used in the context of particle physics and refers to the mass of a particle as it would be measured in a specific way. More precisely, the pole mass is defined as the mass of a particle that corresponds to the position of the pole of the particle's propagator in a quantum field theory. The propagator describes how the particle behaves in terms of its interactions with other particles.