Virtual decuplet effects on octet baryon masses in covariant baryon chiral perturbation theory

We extend a previous analysis of the lowest-lying octet baryon masses in covariant baryon chiral perturbation theory by explicitly taking into account the contribution of the virtual decuplet baryons. Up to next-to-next-to-next-to-leading order, the effects of these heavier degrees of freedom are systematically studied. Their effects on the light-quark mass dependence of the octet baryon masses are shown to be relatively small and can be absorbed by the available low-energy constants up to next-to-next-to-next-to-leading order. Nevertheless, a better description of the finite-volume corrections of the lattice QCD data can be achieved, particularly those with small M_φL ($<4$), which is demonstrated by a careful study of the NPLQCD and QCDSF-UKQCD small-volume data. Finally, we show that the predicted pion- and strangeness-baryon sigma terms are only slightly changed by the inclusion of the virtual decuplet baryons.