Baryon masses and pion-nucleon σ-term to second order in the quark masses

We analyze the octet baryon masses and the pion-nucleon σ-term in the framework of heavy baryon chiral perturbation theory. In contrast to previous investigations, we include all terms up-to-and-including quadratic order in the light quark masses. The pertinent low-energy constants are fixed from resonance exchange. This leaves as the only free parameter the baryon mass in the chiral limit, m̊. We find m̊=749 ± 125 MeV together with σπN(0) = 48 ± 10 MeV. We discuss various implications of these results.