Baryon masses and σ-terms in SU(3) BChPT x 1/Nc

Abstract

Baryon masses and nucleon σ-terms are studied with the effective theory that combines the chiral and 1/Nc expansions for three flavors. In particular the connection between the deviation of the Gell-Mann-Okubo relation and the σ-term corresponding to the scalar density associated with the hypercharge is emphasized. The latter is at lowest order related to a mass combination whose low value has given rise to a σ- term puzzle. It is shown that while the nucleon σ-terms have a well behaved low energy expansion, that mass combination is affected by large higher order corrections non-analytic in quark masses. Adding to the analysis lattice QCD baryon masses, it is found that σπN=69(10) MeV and σs has natural magnitude within its relative large uncertainty.

8 pages, 1 table, 1 figure