Dynamically broken chiral symmetry with bag confinement

Abstract

We lay the groundwork for a model of low-lying mesons in the spirit of the MIT bag model but which also takes into account dynamical chiral-symmetry breaking. We depart from the static cavity approximation in that we dynamically break chiral symmetry prior to confinement and we confine only in the $q\overline{q}$ relative coordinate. We show that single-gluon exchange in the $q\overline{q}$ system is a strong component of the force that drives the symmetry breaking. We verify that our approximations respect the chiral Ward identity prior to confinement. For the pion, we find that our boundary condition on the relative coordinate results in a small chiral breaking in that it raises the pion mass from zero to \ensuremath{\sim}120 MeV.