Nucleon matrix elements and baryon masses in the Dirac orbital model

Abstract

Using the expansion of the baryon wave function in a series of products of single-quark bispinors (Dirac orbitals), the nonsinglet axial and tensor charges of a nucleon are calculated. The leading term yields g _A = 1.27 in good agreement with experiment. Calculation is essentially parameter-free and depends only on the strong coupling constant value α _s . The importance of lower Dirac bispinor component, yielding 18% to the wave-function normalization is stressed. As a check, the baryon decupletmasses in the formalism of this model are also computed using standard values of the string tension σ and the strangequark mass m _s ; the results being in a good agreement with experiment.