Radially excited baryons in the MIT bag model

Abstract

We investigate radially excited baryon states in the cavity approximation to the MIT bag, with particular reference to the phenomenology of $\mathrm{NP}11\mathrm{}$ states. We show that, contrary to earlier surmìse, exchange gluon contributions to the energy are important. The model predicts $\mathrm{NP}11\mathrm{}$ states at 1525 and 1631 MeV in fair agreement with $\pi N$ phase-shift analyses, both states having nonvanishing photoproduction matrix elements. We also examine the coupling of breathing modes of the bag and conclude that their effect is small on phenomenological grounds.