Baryon masses and σ terms in SU(3) BChPT × 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 associated with the scalar density u¯u+d¯d−2s¯s 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 relatively large uncertainty. Keywords: Sigma terms, Nucleon mass, Baryon masses, Gell-Mann–Okubo mass formula