Critical analysis of baryon masses and sigma-terms in heavy baryon chiral perturbation theory

Abstract

We present an analysis of the octet baryon masses and the πN andKN σ-terms in the framework of heavy baryon chiral perturbation theory. At next-to-leading order,O(q ³), knowledge of the baryon masses and σ_πN (0) allows to determine the three corresponding finite low-energy constants and to predict the twoKN σ-terms σ ^(1,2) _KN (0). We also include the spin-3/2 decuplet in the effective theory. The presence of the non-vanishing energy scale due to the octet-decuplet splitting shifts the average octet baryon mass by an infinite amount and leads to infinite renormalizations of the low-energy constants. The first observable effect of the decuplet intermediate states to the baryon masses starts out at orderq ⁴. We argue that it is not sufficient to retain only these but no other higher order terms to achieve a consistent description of the three-flavor scalar sector of baryon CHPT. In addition, we critically discuss anSU (2) result which allows to explain the large shift σ_πN (2M ²_π )-σ_πN (0) via intermediate Δ (1232) states.