How to define physical properties of unstable particles

Abstract

In the framework of effective quantum field theory we address the definition of physical quantities characterizing unstable particles. With the aid of a one-loop calculation, we study this issue in terms of the charge and the magnetic moment of a spin-1/2 resonance. By appealing to the invariance of physical observables under field redefinitions we demonstrate that physical properties of unstable particles should be extracted from the residues at complex (double) poles of the corresponding S-matrix.

11 pages, 3 figures, REVTeX 4

References in corpus (6)

• Electromagnetic excitation of the Delta(1232)-resonance
• Chiral Perturbation Theory: Introduction and Recent Results in the One-Nucleon Sector
• Electroproduction of the N*(1535) resonance at large momentum transfer
• Pole Mass, Width, and Propagators of Unstable Fermions
• The physical meaning of scattering matrix singularities in coupled-channel formalisms
• On the definition of the Δmass and width

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