On mass corrections and the axial coupling constant in the chiral quark model

Abstract

We investigate the higher order corrections to the baryon masses and the baryon axial coupling constant g A in a perturbative treatment of the Goldstone pion field. The zeroth-order quark equations of motion in the chiral quark bag model gives the MIT bag results. The next order gives the dominant corrections to the masses and g A . We show that the perturbation expansion of the pion field is justified for large quark bag radii R, but even for R ∼ 1 fm these higher order corrections calculated here are not negligible. A new spacial configuration for the quarks is introduced by the pion tensor force between different up and/or down quarks. The result is that the quarks in baryons have a mixture of S- and D-state wave functions which have important implications on, e.g., g A and the magnetic moments for different baryons as discussed by Glashow. Only baryons with two or more u/d quarks can have D-states. We neglect the tensor forces (and D-states) implied by the gluon exchange between quarks in this discussion.