Problems of describing spin-(3/2 baryon resonances in the effective Lagrangian theory

Abstract

We investigate some important theoretical issues associated with the treatment of the spin-(3/2 baryons in the effective Lagrangian theory. These are the form of the spin-(3/2 particle propagator, off-shell parameters involving the spin-(3/2 field; strategies of implementing gauge invariance, and unitarity. We comment on previous works by Peccei, Nath et al., Williams, and Adelseck et al., the last three works being in the context of recent revival of interest of baryon resonance structure in quantum chromodynamics. Our experience on the \ensuremath{\Delta}(1232) resonance is invoked as a concrete example of dealing with these problems. Examples of some related problems in theories of massive vector and spin-(3/2 particles, in pion decay and supersymmetry, respectively, are also discussed. These discussions should trigger new theoretical and experimental investigations in the study of baryon resonances excited from free hadrons and in complex nuclei.