Misconceptions regarding spin 3/2

Abstract

Recent work involving virtual excitation of a spin (3/2) baryon resonance is seen to contain two distinct problems. The Feynman propagator for spin (3/2) from the Rarita-Schwinger formalism has often been mistaken for its on-mass-shell limit. In nonrelativistic work the direct channel exchange of a Δ resonance is normally included, but with the exclusion of a term for the intermediate anti-Δ. It is shown that both of these terms are of equal importance in the resonance region for the case of nucleon Compton scattering.