Baryon Masses and Axial Couplings in the Combined 1/Nc and Chiral Expansions

Understand

The effective theory for baryons with combined 1/Nc and chiral expansions is analyzed for non-strange baryons.

• Results for baryon masses and axial couplings are obtained in the small scale expansion, to be coined as the \xi-expansion, in which the 1/Nc and the low energy power countings are linked according to 1/Nc=O(\xi)=O(p).
• Masses and axial couplings are analyzed to O(\xi^3) and O(\xi^2) respectively, which correspond to next-to-next to leading order evaluations, and require one-loop contributions in the effective theory.
• The role of the spin-flavor approximate symmetry in baryons, consequence of the large Nc limit, is manifested in the physical world with Nc=3 in a significant way, as the analysis of its breaking in the masses and the axial couplings shows.