Effects of Baryon-Meson Intermediate States on Baryon Masses

Abstract

The mass shifts of experimentally well-known baryons due to meson-baryon self-energy loops are calculated, and their impact on the observed splitting of the baryon spectrum is studied. Configuration-mixed wave functions adapted from a `relativized' model are used with the 3P0 model to provide predictions for the strength and analytical momentum dependence of the strong vertices. Intermediate states include all the lightest pseudoscalar and vector mesons and corresponding baryons required to provide a complete set of spin-flavor symmetry related baryon-meson states. The sum over intermediate-state baryons is extended to include the second (N=3) band of negative-parity excited states, to provide the most complete calculation of its kind to date. It is found that with reduced-strength one-gluon-exchange interactions between the quarks, roughly half of the splitting between the nucleon and Delta ground states arises from loop effects. The effects of such loops on the spectrum of negative-parity excited states are also studied, and it is found that the resulting splittings are sensitive to configuration mixing caused by the residual interactions. With the extensive set of intermediate baryon-meson states used, a reasonable correspondence is found between model masses and the bare masses required to fit the masses of the states extracted from data analyses.